Thyroid hormones in fetal growth and prepartum maturation

Parabens effects on female reproductive health - Review of evidence from epidemiological and rodent-based studies

Parabens have been used as antimicrobial preservatives since the 1920s. The prevalent use of parabens increases their detection in the environment and in women's biological samples including reproductive tissues. Recent studies suggest parabens may alter endocrine function and thus female reproductive health may be affected. In this literature review, we summarize findings on parabens and female reproduction while focusing on epidemiological and rodent-based studies. The topics reviewed include paraben effects on cyclicity, pregnancy, newborn and pubertal development, reproductive hormones, and ovarian and uterine specific outcomes. Overall, the scientific literature on paraben effects on female reproduction is limited and with some conflicting results. Yet, some epidemiological and/or rodent-based experimental studies report significant findings in relation to paraben effects on cyclicity, fertility, gestation length, birth weight, postnatal development and pubertal onset, hormone levels, and hormone signaling in reproductive tissues. Future epidemiological and experimental studies are needed to better understand paraben effects on female reproduction while focusing on human related exposures including mixtures, physiologic concentrations of parabens, and multi-generational studies.

Maternal high fat-high energy diet alters metabolic factors in the non-human primate fetal heart

The consumption of high fat-high energy diets (HF-HEDs) continues to rise worldwide and parallels the rise in maternal obesity (MO) that predisposes offspring to cardiometabolic disorders. Although the underlying mechanisms are unclear, thyroid hormones (TH) modulate cardiac maturation in utero. Therefore, we aimed to determine the impact of a high fat-high energy diet (HF-HED) on the hormonal, metabolic and contractility profile of the non-human primate (NHP) fetal heart. At ∼9 months preconception, female baboons (Papio hamadryas) were randomly assigned to either a control diet or HF-HED. At 165 days gestational age (term = 184 days), fetuses were delivered by Caesarean section under anaesthesia, humanely killed, and left ventricular cardiac tissue (Control (n = 6 female, 6 male); HF-HED (n = 6 F, 6 M)) was collected. Maternal HF-HED decreased the concentration of active cardiac TH (i.e. triiodothyronine (T3)), and type 1 iodothyronine deiodinase (DIO1) mRNA expression. Maternal HF-HED decreased the abundance of cardiac markers of insulin-mediated glucose uptake phosphorylated insulin receptor substrate 1 (Ser789) and glucose transporter 4, and increased protein abundance of key oxidative phosphorylation complexes (I, III, IV) and mitochondrial abundance in both sexes. Maternal HF-HED alters cardiac TH status, which may induce early signs of cardiac insulin resistance. This may increase the risk of cardiometabolic disorders in later life in offspring born to these pregnancies. KEY POINTS: Babies born to mothers who consume a high fat-high energy diet (HF-HED) prior to and during pregnancy are predisposed to an increased risk of cardiometabolic disorders across the life course. Maternal HF-HED prior to and during pregnancy decreased thyroid hormone triiodothyronine (T3) concentrations and type 1 iodothyronine deiodinase DIO1 mRNA expression in the non-human primate fetal heart. Maternal HF-HED decreased markers of insulin-dependent glucose uptake, phosphorylated insulin receptor substrate 1 and glucose transporter 4 in the fetal heart. Maternal HF-HED increased mitochondrial abundance and mitochondrial OXPHOS complex I, III and IV in the fetal heart. Fetuses from HF-HED pregnancies are predisposed to cardiometabolic disorders that may be mediated by changes in T3, placing them on a poor lifetime cardiovascular health trajectory.

Sex-specific effect of maternal thyroid peroxidase antibody exposure during pregnancy on 5- to 6-year-old children's cardiometabolic risk score: the Ma'anshan birth cohort study

OBJECTIVE

To explore the association between maternal thyroid peroxidase antibody (TPOAb) exposure and 5- to 6-year-old children's cardiometabolic risk (CMR).

METHODS

A total of 2129 mother-child pairs were recruited from the Ma'anshan Birth Cohort (MABC) study. Serum TPOAb was retrospectively measured in pregnant women using an electrochemiluminescence immunoassay. CMR score was evaluated by the serum glycolipids, blood pressure, and waist circumference for children aged 5-6 years. Growth mixture modelling was used to fit trajectories of TPOAb levels throughout pregnancy. Multiple linear regression models and logistic regression models were used for statistical analyses.

RESULTS

Two thousand one hundred twenty-nine mother-child pairs (mean [SD] age, 26.6 [3.6] years) were enrolled for the final study. Maternal TPOAb exposure in the first trimester increased children's overall CMR, glucose level, HOMA-IR, triglyceride level, boys' overall CMR, boys' glucose level, and girls' glucose level. TPOAb exposure in the first trimester was also associated with lower boys' high-density lipoprotein cholesterol (HDL-C) level. In the second trimester, maternal TPOAb exposure was positively associated with children's triglyceride level. Compared with low TPOAb trajectory, children with high maternal TPOAb trajectory had an increased risk of developing high CMR (OR = 3.40; 95% CI, 1.30-8.90), hyperglycemia (OR = 5.20; 95% CI, 2.20-12.28), insulin-resistance (adjusted OR = 2.12; 95% CI, 1.10-4.07), and hypertriglyceridemia (OR = 2.55; 95% CI, 1.06-6.14).

CONCLUSIONS

The first trimester of pregnancy is a critical period for maternal TPOAb exposure to affect CMR in children, with some sex specificity, mainly to the detriment of boys.

Neonatal Thyrotoxicosis in Infants of Mothers with Graves' Disease Treated for Radioiodine-Induced Hypothyroidism: A Literature Review

Fetal and neonatal thyrotoxicosis occurs in up to 5% of pregnancies in mothers with Graves' disease (GD). This condition is caused by stimulating antibodies against the thyrotropin receptor (TRAbs) that cross the placenta and may stimulate the fetal thyroid, typically in the second half of pregnancy. GD is often treated with radioiodine, resulting in hypothyroidism in most patients, but TRAbs can persist for several years. Even if a pregnant mother is hypothyroid after radioiodine therapy or surgery, her TRAbs can still, although rarely, induce fetal hyperthyroidism. In this review, we first present two cases of neonatal hyperthyroidism in mothers with GD who became hypothyroid after prior radioiodine therapy, identified through a 10-year analysis of the National Perinatal System in Slovenia. Based on these cases, we provide an overview of existing data on this rare clinical condition in neonates. We also discuss the underlying mechanisms and clinical outcomes based on currently available data. In conclusion, our review highlights the importance of careful monitoring during pregnancy in all women with GD, even in those well managed after radioiodine therapy or surgery.

Effect of thyroid disruption on ovarian development following maternal exposure to Bisphenol S

Thyroid hormones play a crucial role in numerous physiological processes, including reproduction. Bisphenol S (BPS) is a structural analog of Bisphenol A known for its toxic effects. Interference of this substitute with normal thyroid function has been described. To investigate the effect of thyroid disruption on ovarian development following maternal exposure to BPS, female rats were exposed, daily, to either AT 1-850 (a thyroid hormone receptor antagonist) (10 nmol/rat) or BPS (0.2 mg/kg) during gestation and lactation. The effects on reproductive outcome, offspring development, histological structures, hormone levels, oxidative status, cytoskeleton proteins expression, and oocyte development gene expression were examined. Our results are in favor of offspring ovarian development disruption due to thyroid disturbance in adult pregnant females. During both fetal and postnatal stages, BPS considerably altered the histological structure of the thyroid tissue as well as oocyte and follicular development, which led to premature ovarian failure and stimulation of oocyte atresia, being accompanied with oxidative stress, hypothalamic-pituitary-ovarian axis disorders, and cytoskeletal dynamic disturbance. Crucially, our study underscores that BPS may induce reproductive toxicity by blocking nuclear thyroid hormone receptors, evidenced by the parallelism and the perfect meshing between the data obtained following exposure to AT 1-850 and those after the treatment by this substitute.

Association between pre- and postnatal exposure to endocrine-disrupting chemicals and birth and neurodevelopmental outcomes: an extensive review

Endocrine-disrupting chemicals (EDCs) are natural or synthetic chemicals that mimic, block, or interfere with the hormones in the body. The most common and well- studied EDCs are bisphenol A, phthalates, and persistent organic pollutants including polychlorinated biphenyls, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances, other brominated flame retardants, organochlorine pesticides, dioxins, and furans. Starting in embryonic life, humans are constantly exposed to EDCs through air, diet, skin, and water. Fetuses and newborns undergo crucial developmental processes that allow adaptation to the environment throughout life. As developing organisms, they are extremely sensitive to low doses of EDCs. Many EDCs can cross the placental barrier and reach the developing fetal organs. In addition, newborns can be exposed to EDCs through breastfeeding or formula feeding. Pre- and postnatal exposure to EDCs may increase the risk of childhood diseases by disrupting the hormone-mediated processes critical for growth and development during gestation and infancy. This review discusses evidence of the relationship between pre- and postnatal exposure to several EDCs, childbirth, and neurodevelopmental outcomes. Available evidence suggests that pre- and postnatal exposure to certain EDCs causes fetal growth restriction, preterm birth, low birth weight, and neurodevelopmental problems through various mechanisms of action. Given the adverse effects of EDCs on child development, further studies are required to clarify the overall associations.

HDAC1/2/3-mediated downregulation of neurogranin is involved in cognitive impairment in offspring exposed to maternal subclinical hypothyroidism

Subclinical hypothyroidism (SCH) in pregnancy is the most common form of thyroid dysfunction in pregnancy, which can affect fetal nervous system development and increase the risk of neurodevelopmental disorders after birth. However, the mechanism of the effect of maternal subclinical hypothyroidism on fetal brain development and behavioral phenotypes is still unclear and requires further study. In this study, we constructed a mouse model of maternal subclinical hypothyroidism by exposing dams to drinking water containing 50 ppm propylthiouracil (PTU) during pregnancy and found that its offspring were accompanied by severe cognitive deficits by behavioral testing. Mechanistically, gestational SCH resulted in the upregulation of protein expression and activity of HDAC1/2/3 in the hippocampus of the offspring. ChIP analysis revealed that H3K9ac on the neurogranin (Ng) promoter was reduced in the hippocampus of the offspring of SCH, with a significant reduction in Ng protein, leading to reduced expression levels of synaptic plasticity markers PSD95 (a membrane-associated protein in the postsynaptic density) and SYN (synaptophysin, a specific marker for presynaptic terminals), and impaired synaptic plasticity. In addition, administration of MS-275 (an HDAC1/2/3-specific inhibitor) to SCH offspring alleviated impaired synaptic plasticity and cognitive dysfunction in offspring. Thus, our study suggests that maternal subclinical hypothyroidism may mediate offspring cognitive dysfunction through the HDAC1/2/3-H3K9ac-Ng pathway. Our study contributes to the understanding of the signaling mechanisms underlying maternal subclinical hypothyroidism-mediated cognitive impairment in the offspring.

Association between maternal and cord blood thyroid hormones, and urine iodine concentration with fetal growth

OBJECTIVES

We planned to evaluate the association of fetal and maternal thyroid hormones and maternal iodine status with neonates' anthropometric parameters.

METHODS

In this cross-sectional study, levels of thyrotropin were measured in maternal serum in the first trimester of pregnancy, and thyrotropin (TSH) and free thyroxin (fT4) were measured in cord blood serum samples at birth. Urinary iodine concentration (UIC) levels in random urine samples of mothers were measured in the third trimester of pregnancy. The relationship between UIC and thyroid hormone levels of mothers with neonates' anthropometric birth parameters of neonates was evaluated.

RESULTS

One hundred eighty-eight mother-newborn pairs completed the study. Mean (SD) of cord blood TSH (CB-TSH), cord blood-free thyroxin (CB-FT4) values, and maternal TSH (M-TSH) levels were 8.8 (7.3) mIU/L, 1.01 (0.2) ng/dL, and 2.2 (0.9) mIU/L, respectively. After adjusting for confounders, there was a positive significant association between female neonate length and maternal TSH and log log-transformed CB TSH (LN_CB-TSH) (p<0.05). Median UIC (Q1-Q3) was 157 (53-241) μg/L, and there was no association between birth weight, birth length, and head circumferences of neonates and mothers' UIC (p>0.05).

CONCLUSIONS

We found a positive correlation between maternal TSH in the first trimester of pregnancy and the birth length of newborns, and a negative correlation was observed between CB-TSH and birth length in girls, but it did not provide conclusive evidence for the relationship between maternal and neonatal thyroid hormone levels and birth weight. There was no association between maternal UIC levels in the third trimester and birth anthropometric parameters.

Lack of beneficiary effect of levothyroxine therapy of pregnant women with subclinical hypothyroidism in terms of neurodevelopment of their offspring

PURPOSE

Despite the beneficial effects of levothyroxine (LT4) therapy on pregnancy outcomes of women with subclinical hypothyroidism (SCH), its impact on the developmental status of offspring remains unclear. We aimed to assess the effects of LT4 therapy on the neurodevelopment of infants of SCH women in the first 3 years of life.

METHODS

A follow-up study was conducted on children born to SCH pregnant women who had participated in a single-blind randomized clinical trial (Tehran Thyroid and Pregnancy Study). In this follow-up study, 357 children of SCH mothers were randomly assigned to SCH + LT4 (treated with LT4 after the first prenatal visit and throughout pregnancy) and SCH-LT4 groups. Children born of euthyroid TPOAb-women served as the control group (n = 737). The neurodevelopment status of children was assessed in five domains (communication, gross motor, fine motor, problem-solving, and social-personal domains) using the Ages and Stages Questionnaires (ASQ) at the age of 3 years.

RESULTS

Pairwise comparisons of ASQ domains between euthyroid, SCH + LT4, and SCH-LT4 groups show no statistically significant difference between groups in the total score [median 25-75 total score: 265 (240-280); 270 (245-285); and 265 (245-285); P-value = 0.2, respectively]. The reanalyzing data using the TSH cutoff value of 4.0 mIU/L indicated no significant difference between groups in the score of ASQ in each domain or total score with TSH levels < 4.0 mIU/L, however, a statistically significant difference in the median score of the gross motor was observed between those SCH + LT4 with baseline TSH values ≥ 4.0 mIU/L and SCH-LT4 [60 (55-60) vs. 57.5 (50-60); P = 0.01].

CONCLUSIONS

Our study does not support the beneficiary effect of LT4 therapy for SCH pregnant women in terms of the neurological development of their offspring in the first three years of life.

Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals

Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.

Association of Gestational Free and Total Triiodothyronine With Gestational Hypertension, Preeclampsia, Preterm Birth, and Birth Weight: An Individual Participant Data Meta-analysis

CONTEXT

Triiodothyronine (T3) is the bioactive form of thyroid hormone. In contrast to thyroid-stimulating hormone and free thyroxine, we lack knowledge on the association of gestational T3 with adverse obstetric outcomes.

OBJECTIVE

To investigate the associaiton of gestational free or total T3 (FT3 or TT3) with adverse obstetric outcomes.

METHODS

We collected individual participant data from prospective cohort studies on gestational FT3 or TT3, adverse obstetric outcomes (preeclampsia, gestational hypertension, preterm birth and very preterm birth, small for gestational age [SGA], and large for gestational age [LGA]), and potential confounders. We used mixed-effects regression models adjusting for potential confounders.

RESULTS

The final study population comprised 33 118 mother-child pairs of which 27 331 had data on FT3 and 16 164 on TT3. There was a U-shaped association of FT3 with preeclampsia (P = .0069) and a J-shaped association with the risk of gestational hypertension (P = .029). Higher TT3 was associated with a higher risk of gestational hypertension (OR per SD of TT3 1.20, 95% CI 1.08 to 1.33; P = .0007). A lower TT3 but not FT3 was associated with a higher risk of very preterm birth (OR 0.72, 95% CI 0.55 to 0.94; P = .018). TT3 but not FT3 was positively associated with birth weight (mean difference per 1 SD increase in TT3 12.8, 95% CI 6.5 to 19.1 g, P < .0001) but there was no association with SGA or LGA.

CONCLUSION

This study provides new insights on the association of gestational FT3 and TT3 with major adverse pregnancy outcomes that form the basis for future studies required to elucidate the effects of thyroid function on pregnancy outcomes. Based on the current study, routine FT3 or TT3 measurements for the assessment of thyroid function during pregnancy do not seem to be of added value in the risk assessment for adverse outcomes.

Clinical Characteristics and Risk Factors Associated With Adverse Pregnancy Outcomes in Patients With Gestational Hypothyroidism: A Case-Control Study

OBJECTIVE

To synthesize evidence, summarize the clinical features of patients diagnosed with gestational hypothyroidism (GH), and analyze the risk factors associated with adverse pregnancy outcomes.

METHODS

From February 2021 to March 2023, a case-control study was conducted on 298 hospitalized patients with GH and 312 pregnant women without GH who underwent physical examinations. The 312 pregnant women without GH were randomly selected during the same time period. They were allocated into the study and control groups for further comparison of clinical characteristics and pregnancy outcomes.

RESULTS

The parameters, including age, gestational diabetes, gestational hypertension, gravidity, parity, spontaneous abortion, history of gestation, thyroid-stimulating hormone, free triiodothyronine, thyroid peroxidase antibody (TPO-Ab), and free thyroxine were significantly different between the 2 groups (P <.05). Moreover, significant differences were found between the 2 groups in terms of preterm delivery, preeclampsia, premature rupture of membranes, placental abruption, and postpartum hemorrhage (P <.05). The multivariate logistic regression analysis revealed that the influencing factors of pregnancy outcome in patients with GH were age (≥30 years), gestational diabetes, gestational hypertension, gravidity (≥3 times), spontaneous abortion, parity, history of gestation (multiparity), and TPO-Ab (positive).

CONCLUSION

Our study revealed that the clinical features of patients with GH were age, gestational diabetes, gestational hypertension, gravidity, parity, spontaneous abortion, history of gestation, thyroid-stimulating hormone, free triiodothyronine, TPO-Ab, and free thyroxine.

Molecular pathways in placental-fetal development and disruption

The first trimester of pregnancy ranks high in priority when minimizing harmful exposures, given the wide-ranging types of organogenesis occurring between 4- and 12-weeks' gestation. One way to quantify potential harm to the fetus in the first trimester is to measure a corollary effect on the placenta. Placental biomarkers are widely present in maternal circulation, cord blood, and placental tissue biopsied at birth or at the time of pregnancy termination. Here we evaluate ten diverse pathways involving molecules expressed in the first trimester human placenta based on their relevance to normal fetal development and to the hypothesis of placental-fetal endocrine disruption (perturbation in development that results in abnormal endocrine function in the offspring), namely: human chorionic gonadotropin (hCG), thyroid hormone regulation, peroxisome proliferator activated receptor protein gamma (PPARγ), leptin, transforming growth factor beta, epiregulin, growth differentiation factor 15, small nucleolar RNAs, serotonin, and vitamin D. Some of these are well-established as biomarkers of placental-fetal endocrine disruption, while others are not well studied and were selected based on discovery analyses of the placental transcriptome. A literature search on these biomarkers summarizes evidence of placenta-specific production and regulation of each biomarker, and their role in fetal reproductive tract, brain, and other specific domains of fetal development. In this review, we extend the theory of fetal programming to placental-fetal programming.

Interactive transgenerational effects of parental co-exposure to prochloraz and chlorpyrifos: Disruption in multiple biological processes and induction of genotoxicity

The application of different types of pesticides can result in the coexistence of multiple pesticide residues in our food and the environment. This can have detrimental effects on the health of offspring across generations when parents are exposed to these pesticides. Therefore, it is imperative to understand the long-term effects that can be inherited by future generations when assessing the risks associated with pesticides. To study the genotoxic effects of commonly used pesticides, prochloraz (PRO) and chlorpyrifos (CHL), and assess whether their combined exposures have a different toxic effect, we modeled the transgenerational effects of parental (F0-generation) and/or offspring (F1-generation) exposures on zebrafish embryos in the F1-generation. Following the exposures, we proceeded to assess the impacts of these exposures on a range of biological processes in F1-generation zebrafish. Our results revealed that exposure to PRO and CHL altered multiple biological processes, such as inflammation, apoptosis, oxidative stress, and thyroid hormone synthesis, and detoxification system, providing molecular targets for subsequent studies on toxicity mechanisms. Notably, our study also found that the biological processes of F1-generation zebrafish embryos were altered even though they were not exposed to any pesticide when F0-generation zebrafish were exposed to PRO or CHL, suggesting potential genotoxicity. In conclusion, we provided in-vivo evidence that parental exposure to PRO and/or CHL can induce genotoxicity in the offspring. Moreover, we observed that the toxic effects resulting from the combined exposure were interactive, suggesting a potential synergistic impact on the offspring.

Associations of Organophosphate Ester Flame Retardant Exposures during Pregnancy with Gestational Duration and Fetal Growth: The Environmental influences on Child Health Outcomes (ECHO) Program

BACKGROUND

Widespread exposure to organophosphate ester (OPE) flame retardants with potential reproductive toxicity raises concern regarding the impacts of gestational exposure on birth outcomes. Previous studies of prenatal OPE exposure and birth outcomes had limited sample sizes, with inconclusive results.

OBJECTIVES

We conducted a collaborative analysis of associations between gestational OPE exposures and adverse birth outcomes and tested whether associations were modified by sex.

METHODS

We included 6,646 pregnant participants from 16 cohorts in the Environmental influences on Child Health Outcomes (ECHO) Program. Nine OPE biomarkers were quantified in maternal urine samples collected primarily during the second and third trimester and modeled as log 2 -transformed continuous, categorized (high/low/nondetect), or dichotomous (detect/nondetect) variables depending on detection frequency. We used covariate-adjusted linear, logistic, and multinomial regression with generalized estimating equations, accounting for cohort-level clustering, to estimate associations of OPE biomarkers with gestational length and birth weight outcomes. Secondarily, we assessed effect modification by sex.

RESULTS

Three OPE biomarkers [diphenyl phosphate (DPHP), a composite of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP), and bis(1,3-dichloro-2-propyl) phosphate] were detected in > 85 % of participants. In adjusted models, DBUP/DIBP [odds ratio (OR) per doubling = 1.07 ; 95% confidence interval (CI): 1.02, 1.12] and bis(butoxyethyl) phosphate (OR for high vs. nondetect = 1.25 ; 95% CI: 1.06, 1.46), but not other OPE biomarkers, were associated with higher odds of preterm birth. We observed effect modification by sex for associations of DPHP and high bis(2-chloroethyl) phosphate with completed gestational weeks and odds of preterm birth, with adverse associations among females. In addition, newborns of mothers with detectable bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate had higher birth weight-for-gestational-age z -scores (β for detect vs. nondetect = 0.04 - 0.07 ); other chemicals showed null associations.

DISCUSSION

In the largest study to date, we find gestational exposures to several OPEs are associated with earlier timing of birth, especially among female neonates, or with greater fetal growth. https://doi.org/10.1289/EHP13182.

Additional effects using progestins in mares on levels of thyroid hormones and steroids in neonates

The risk of pregnancy loss in mares leads to the use of exogenous hormones to help pregnancy maintenance. The objective was to evaluate the proportion of thyroid hormones and steroids in neonates, in the following postpartum period, born to mares fed with synthetic progesterone and to verify the existence of a correlation between the level of progesterone between mother and neonate. Twenty-seven mares and their foals were used. The animals were divided into 5 experimental groups: group 1 (control, without hormonal supplementation), group 2 (random samples fed to 120 days of pregnancy with long-term progesterone), group 3 (mares fed with short-term progesterone as of 280.º day of pregnancy), group 4 (mares fed with long-term progesterone as of 280.º day of pregnancy) and group 5 (mares fed with synthetic hormone [altrenogest] as of 280.º day of pregnancy). The animal's blood collection took place immediately after parturition for the hormonal measurement. The hormones measured in neonates were total T3, free T4, TSH, progesterone and cortisone. In mares, only levels of progesterone. The groups of neonates showed no difference on levels of total T3, free T4, TSH and progesterone. There was no difference on levels of progesterone in mares among the groups. Neonates from groups 4 and 5 had higher and lower cortisone levels, respectively. No neonate showed clinical change. There was also no correlation between levels of progesterone in mares and foals. Thus, hormonal supplementation with long-term progesterone as of 280 days of pregnancy leds to an increase in the neonate's cortisone levels, in the meantime, supplementation with altrenogest as of 280 days of pregnancy caused a decrease on cortisone levels in foals, despite clinical signs have not been observed on these animals.

Maternal isolated hypothyroxinemia in the first trimester is not associated with adverse pregnancy outcomes, except for macrosomia: a prospective cohort study in China

Objective

Insufficient thyroid hormone levels during pregnancy, especially in the first trimester, adversely affect maternal and fetal health. However, the impact of isolated hypothyroxinemia (IH) on adverse pregnancy outcomes remains controversial. Therefore, this study aimed to investigate the association between IH during the first trimester and adverse pregnancy outcomes.

Methods

This prospective cohort study included 1236 pregnant women. Thyroid-stimulating hormone and free thyroxine levels were measured before 13 weeks of gestation. Logistic regression analysis and the Cochran-Armitage trend test were used to assess the association between IH in the first trimester and adverse pregnancy outcomes.

Results

IH during the first trimester was associated with an increased risk of macrosomia. After adjusting for confounding factors, including age, body mass index, parity, abnormal pregnancy history, fasting blood glucose, and total cholesterol, multivariate logistic regression analysis showed that IH in the first trimester remained an independent risk factor for macrosomia. In addition, the risk of macrosomia increased with IH severity. However, no significant relationship was found between IH during the first trimester and gestational diabetes mellitus, hypertensive disorders of pregnancy, spontaneous abortion, premature rupture of membranes, placental abruption, oligohydramnios, premature delivery, fetal distress, or low birth weight.

Conclusion

IH during the first trimester did not increase the risk of adverse pregnancy outcomes, except for macrosomia.

Transcriptomic Changes in Response to Form of Selenium on the Interferon-Tau Signaling Mechanism in the Caruncular Tissue of Beef Heifers at Maternal Recognition of Pregnancy

We have reported that selenium (Se) provided to grazing beef cattle in an inorganic (ISe) form versus a 1:1 mixture (MIX) of inorganic and organic (OSe) forms affects cholesterol biosynthesis in the corpus luteum (CL), the abundance of interferon tau (IFNτ) and progesterone (P4)-induced mRNAs in the caruncular (CAR) tissue of the endometrium, and conceptus length at maternal recognition of pregnancy (MRP). In this study, beef heifers were supplemented with a vitamin-mineral mix containing 35 ppm Se as ISe or MIX to achieve a Se-adequate status. Inseminated heifers were killed at MRP (d 17, n = 6 per treatment) for tissue collection. In CAR samples from MIX versus ISe heifers, qPCR revealed that mRNA encoding the thyroid regulating DIO2 and DIO3 was decreased (p < 0.05) and a complete transcriptomic analysis revealed effects on the interferon JAK-STAT1/2 pathway, including decreased expression of mRNAs encoding the classical interferon stimulated genes IFIT1, IFIT2, IFIT3, IRF1, IRF9, ISG15, OAS2, and RSAD2 (p < 0.05). Treatment also affected the abundance of mRNAs contributing to the immunotolerant environment (p < 0.05). In combination, these findings suggest more advanced preparation of the CAR and developing conceptus for implantation and to evade immune rejection by the maternal system in MIX- vs. ISe-treated heifers.

Association of maternal thyroid disease with obesity in child

OBJECTIVES

During pregnancy, many women develop thyroid disorders, which can result in fetal and neonatal development defects. We investigated whether maternal thyroid dysfunction would affect their children's growth and obesity.

STUDY DESIGN

We conducted a nationwide population-based cohort study using a combination of data from several Korean nationwide registries to investigate the association between maternal thyroid dysfunction, offspring growth, and obesity. Childhood growth was repeatedly measured at three periods of age from 42 to 80 months, using body mass index (BMI).

RESULTS

A total of 1,123,499 women were enrolled in this study; 78,902 (7.0 %) had pre-pregnancy thyroid disease. Significant association was found between maternal hyperthyroidism and obesity in all children aged 42-66 months (42-54 months, adjusted odds ratio (aOR) 0.93, 95 % confidence interval (CI) 0.89-0.98; 54-66 months, aOR 0.93, 95 % CI 0.87-0.99), but not at later ages. In the analysis by sex, maternal hyperthyroidism was associated with childhood obesity in boys, whereas it was not associated with those in girls of any age. No association was observed between maternal hypothyroidism and child BMI or obesity.

CONCLUSIONS

The association between maternal thyroid function and obesity in offspring is attenuated from early to late childhood, suggesting that many other factors may be involved in developing childhood obesity.

Assessment of the Iodine Status of Lactating Women and Infants in Shanghai, China

There is a risk of iodine deficiency among pregnant women in China. However, research on the iodine status of lactating women and infants is scarce. In this study, we aimed to evaluate the iodine status of lactating women and their infants and explore the relationship between breast milk iodine concentrations (BMICs) and urinary iodine concentrations (UICs). In total, 257 lactating women and their infants were recruited from the Shanghai Sixth People's Hospital East campus between May 2018 and May 2019. The BMIC and UIC were measured by inductively coupled plasma‒mass spectrometry (ICP‒MS). One-day 24-h dietary recall was used to determine the dietary intake of iodine. The mean dietary intake of iodine among the lactating women was 145.1 μg/day, and 97.83% (n = 225) of the lactating women had a dietary iodine intake below 240 μg/day. The median BMIC and UIC of the lactating women was 150.7 μg/L (interquartile range, IQR 102.9, 205.5) and 110.0 μg/L (IQR 65.8, 171.4), respectively, and the median UIC of the infants was 212.7 μg/L (IQR 142.1, 320.6). The BMIC of lactating women who consumed iodized salt was significantly higher than that of lactating women who did not consume iodized salt (p = 0.015). The infants' UIC values were significantly correlated with the BMIC values (r = 0.597**, p < 0.001). The iodine nutritional status of lactating women and infants in Shanghai was generally sufficient according to the WHO's iodine nutritional status recommendation. The use of iodized salt was related to increasing dietary iodine intake and the BMIC. Improvements in BMICs have positive effects on the nutritional levels of iodine in infants.

A meta-analysis of epigenome-wide association studies on pregnancy vitamin B12 concentrations and offspring DNA methylation

Circulating vitamin B12 concentrations during pregnancy are associated with offspring health. Foetal DNA methylation changes could underlie these associations. Within the Pregnancy And Childhood Epigenetics Consortium, we meta-analysed epigenome-wide associations of circulating vitamin B12 concentrations in mothers during pregnancy (n = 2,420) or cord blood (n = 1,029), with cord blood DNA methylation. Maternal and newborn vitamin B12 concentrations were associated with DNA methylation at 109 and 7 CpGs, respectively (False Discovery Rate P-value <0.05). Persistent associations with DNA methylation in the peripheral blood of up to 482 children aged 4-10 y were observed for 40.7% of CpGs associated with maternal vitamin B12 and 57.1% of CpGs associated with newborn vitamin B12. Of the CpGs identified in the maternal meta-analyses, 4.6% were associated with either birth weight or gestational age in a previous work. For the newborn meta-analysis, this was the case for 14.3% of the identified CpGs. Also, of the CpGs identified in the newborn meta-analysis, 14.3% and 28.6%, respectively, were associated with childhood cognitive skills and nonverbal IQ. Of the 109 CpGs associated with maternal vitamin B12, 18.3% were associated with nearby gene expression. In this study, we showed that maternal and newborn vitamin B12 concentrations are associated with DNA methylation at multiple CpGs in offspring blood (PFDR<0.05). Whether this differential DNA methylation underlies associations of vitamin B12 concentrations with child health outcomes, such as birth weight, gestational age, and childhood cognition, should be further examined in future studies.

Levothyroxine Treatment Among Pregnant Women and Risk of Seizure in Children: A Population-Based Cohort Study

INTRODUCTION AND OBJECTIVE

The risk of seizure in offspring following prenatal exposure to levothyroxine is not well investigated. This study aimed to evaluate the association between levothyroxine treatment among pregnant women and the risk of seizure in their offspring.

METHODS

This population-based cohort study included all pregnant women who delivered a live birth between January 2001 to January 2018, with a follow-up to December 2020, using data from the Hong Kong Clinical Data Analysis and Reporting System. Propensity score fine-stratification weighted hazard ratios (wHR) with 95% confidence intervals (CIs) were presented to assess the association between maternal levothyroxine use during pregnancy and seizures in children.

RESULTS

Among 528,343 included mother-child pairs, 3044 children were prenatally exposed to levothyroxine at any time during the pregnancy period. A significantly increased risk of seizure was observed in children of the prenatally exposed group compared with the prenatally unexposed group (wHR 1.12, 95% CI 1.02-1.22). An increased risk of seizure was observed when comparing the prenatally exposed group with euthyroid mothers who had no history of thyroid-related diagnosis or prescriptions (wHR 1.12, 95% CI 1.02-1.23). However, no significant difference was observed between the prenatally exposed group and those previously exposed to levothyroxine but had stopped during pregnancy (wHR 0.97, 95% CI 0.66-1.44). No significant difference was observed in the sibling-matched analysis either (wHR 1.23, 95% CI 0.76-2.01).

CONCLUSION

The observed increased risk of seizure in children born from mothers exposed to levothyroxine during pregnancy might be due to residual confounding by maternal thyroid disease. The findings support the current guidelines on the safe use of levothyroxine treatment during pregnancy.

Thyroid hormone treatment counteracts cellular phenotypical remodeling in diabetic organs

Diabetes mellitus and alterations in thyroid hormone (TH) signaling are closely linked. Though the role of TH signaling in cell differentiation and growth is well known, it remains unclear whether its alterations contribute to the pathobiology of diabetic cells. Here, we aim to investigate whether the administration of exogenous T3 can counteract the cellular remodeling that occurs in diabetic cardiomyocytes, podocytes, and pancreatic beta cells. Treating diabetic rats with T3 prevents dedifferentiation, pathological growth, and ultrastructural alterations in podocytes and cardiomyocytes. In vitro, T3 reverses glucose-induced growth in human podocytes and cardiomyocytes, restores cardiomyocyte cytoarchitecture, and reverses pathological alterations in kidney and cardiac organoids. Finally, T3 treatment counteracts glucose-induced transdifferentiation, cell growth, and loss in pancreatic beta cells through TH receptor alpha1 activation. Our studies indicate that TH signaling activation substantially counteracts diabetes-induced pathological remodeling, and provide a potential therapeutic approach for the treatment of diabetes and its complications.

Exogenous corticosterone administration during pregnancy in mice alters placental and fetal thyroid hormone availability in females

INTRODUCTION

Maternal prenatal psychological stress is associated with adverse pregnancy outcomes and increased risk of adverse health outcomes in children. While the molecular mechanisms that govern these associations has not been fully teased apart, stress-induced changes in placental function can drive sex-specific phenotypes in offspring. We sought to identify and examine molecular pathways in the placenta that are altered in response to maternal prenatal stress.

METHODS

We previously employed a mouse model of maternal prenatal stress where pregnant dams were treated with stress hormone (CORT) beginning in mid-gestation. Using this model, we conducted RNAseq analysis of whole placenta at E18.5. We used qRT-PCR to validate gene expression changes in the placenta and in a trophoblast cell line. ELISAs were used to measure the abundance of thyroid hormones in maternal and fetal serum and in the placenta.

RESULTS

Dio2 was amongst the top differentially expressed genes in response to exogenous stress hormone. Dio2 expression was more downregulated in placenta of female fetuses from CORT-treated dams than both control placenta from females and placenta from male fetuses. Consistent with Dio2's role in production of bioactive thyroid hormone (T3), we found that there was a reduction of T3 in placenta and serum of female embryos from CORT-treated dams at E18.5. Both T3 and T4 were reduced in the fetal compartment of the placenta of female fetuses from CORT-treated dams at E16.5. Exogenous stress hormone induced reduction in thyroid hormone in females was independent of circulating levels of TH in the dams.

DISCUSSION

The placental thyroid hormone synthesis pathway may be a target of elevated maternal stress hormone and modulate fetal programming of health and disease of offspring in a sex-specific fashion.

Effects of maternal hypothyroidism on postnatal cardiomyocyte proliferation and cardiac disease responses of the progeny

Maternal hypothyroidism (MH) could adversely affect the cardiac disease responses of the progeny. This study tested the hypothesis that MH reduces early postnatal cardiomyocyte (CM) proliferation so that the adult heart of MH progeny has a smaller number of larger cardiac myocytes, which imparts adverse cardiac disease responses following injury. Thyroidectomy (TX) was used to establish MH. The progeny from mice that underwent sham or TX surgery were termed Ctrl (control) or MH (maternal hypothyroidism) progeny, respectively. MH progeny had similar heart weight (HW) to body weight (BW) ratios and larger CM size consistent with fewer CMs at postnatal day 60 (P60) compared with Ctrl (control) progeny. MH progeny had lower numbers of EdU+, Ki67+, and phosphorylated histone H3 (PH3)+ CMs, which suggests they had a decreased CM proliferation in the postnatal timeframe. RNA-seq data showed that genes related to DNA replication were downregulated in P5 MH hearts, including bone morphogenetic protein 10 (Bmp10). Both in vivo and in vitro studies showed Bmp10 treatment increased CM proliferation. After transverse aortic constriction (TAC), the MH progeny had more severe cardiac pathological remodeling compared with the Ctrl progeny. Thyroid hormone (T4) treatment for MH mothers preserved their progeny's postnatal CM proliferation capacity and prevented excessive pathological remodeling after TAC. Our results suggest that CM proliferation during early postnatal development was significantly reduced in MH progeny, resulting in fewer CMs with hypertrophy in adulthood. These changes were associated with more severe cardiac disease responses after pressure overload.NEW & NOTEWORTHY Our study shows that compared with Ctrl (control) progeny, the adult progeny of mothers who have MH (MH progeny) had fewer CMs. This reduction of CM numbers was associated with decreased postnatal CM proliferation. Gene expression studies showed a reduced expression of Bmp10 in MH progeny. Bmp10 has been linked to myocyte proliferation. In vivo and in vitro studies showed that Bmp10 treatment of MH progeny and their myocytes could increase CM proliferation. Differences in CM number and size in adult hearts of MH progeny were linked to more severe cardiac structural and functional remodeling after pressure overload. T4 (synthetic thyroxine) treatment of MH mothers during their pregnancy, prevented the reduction in CM number in their progeny and the adverse response to disease stress.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.

Gene coexpression network analysis reveals perirenal adipose tissue as an important target of prenatal malnutrition in sheep

We have previously demonstrated that pre- and early postnatal malnutrition in sheep induced depot- and sex-specific changes in adipose morphological features, metabolic outcomes, and transcriptome in adulthood, with perirenal (PER) as the major target followed by subcutaneous (SUB) adipose tissue. We aimed to identify coexpressed and hub genes in SUB and PER to identify the underlying molecular mechanisms contributing to the early nutritional programming of adipose-related phenotypic outcomes. Transcriptomes of SUB and PER of male and female adult sheep with different pre- and early postnatal nutrition histories were used to construct networks of coexpressed genes likely to be functionally associated with pre- and early postnatal nutrition histories and phenotypic traits using weighted gene coexpression network analysis. The modules from PER showed enrichment of cell cycle regulation, gene expression, transmembrane transport, and metabolic processes associated with both sexes' prenatal nutrition. In SUB (only males), a module of enriched adenosine diphosphate metabolism and development correlated with prenatal nutrition. Sex-specific module enrichments were found in PER, such as chromatin modification in the male network but histone modification and mitochondria- and oxidative phosphorylation-related functions in the female network. These sex-specific modules correlated with prenatal nutrition and adipocyte size distribution patterns. Our results point to PER as a primary target of prenatal malnutrition compared to SUB, which played only a minor role. The prenatal programming of gene expression and cell cycle, potentially through epigenetic modifications, might be underlying mechanisms responsible for observed changes in PER expandability and adipocyte-size distribution patterns in adulthood in both sexes.

Developmental and environmental modulation of fecal thyroid hormone levels in wild Assamese macaques (Macaca assamensis)

Thyroid hormones are key modulators of development, as well as mediators of environmental conditions, by regulating developmental processes and metabolism in primates. Hormone measurement in noninvasively collected samples, that is, feces and urine, is a valuable tool for studying the endocrine function of wildlife, and recent studies have demonstrated the feasibility of measuring thyroid hormones in fecal samples of zoo-housed and wild nonhuman primates. Our study aimed to (i) validate the measurement of immunoreactive fecal total triiodothyronine (IF-T3) in wild Assamese macaques (Macaca assamensis) and (ii) to investigate its developmental changes and its response to environmental changes, including stress responses, in immature individuals. Fecal samples and environmental parameters were collected from individuals of three social groups of wild Assamese macaques living at Phu Khieo Wildlife Sanctuary, Northeastern Thailand. Our study confirmed the methodological feasibility and biological validity of measuring IF-T3 in this population. Specifically, the biological validation demonstrated higher IF-T3 levels in immatures compared to adults, and higher levels in females during late gestation compared to the preconception stage. Our analysis of IF-T3 levels in developing immature macaques revealed a significant increase with age. Furthermore, we found a positive association between IF-T3 and immunoreactive fecal glucocorticoid levels, an indicator of the physiological stress response. Neither minimum temperature nor fruit abundance predicted variation in IF-T3 levels in the immatures. Our findings indicate the possibility for differing effects of climatic factors and food availability on thyroid hormone level changes in immature versus adult animals and in wild compared to experimental conditions. Overall, our study provides the basis for further investigations into the role of thyroid hormones in shaping species-specific traits, growth, and overall primate development.

Exogenous corticosterone administration during pregnancy alters placental and fetal thyroid hormone availability in females

Introduction

Maternal prenatal stress is associated with adverse pregnancy outcomes and predisposition to long-term adverse health outcomes in children. While the molecular mechanisms that govern these associations has not been fully teased apart, stress-induced changes in placental function can drive sex-specific phenotypes in offspring. We sought to identify and examine molecular pathways in the placenta that are altered in response to maternal prenatal stress.

Methods

Using a mouse model of maternal prenatal stress, we conducted RNA-seq analysis of whole placenta at E18.5. We used qRT-PCR to validate gene expression changes in the placenta and in a trophoblast cell line. ELISAs were used to measure the abundance of thyroid hormones in maternal and fetal serum and in the placenta.

Results

Dio2 was amongst the top differentially expressed genes in response to elevated maternal stress hormone. Dio2 expression was more downregulated in female placenta from stressed dams than both female control and male placenta. Consistent with Dio2's role in production of bioactive thyroid hormone (T3), we found that there was a reduction of T3 in placenta and serum of female embryos from stressed dams at E18.5. Both T3 and T4 were reduced in the fetal compartment of the female placenta from stressed dams at E16.5. Stress hormone induced reduction in thyroid hormone in females was independent of circulating levels of TH in the dams.

Discussion

The placental thyroid hormone synthesis pathway may be a target of maternal stress and modulate fetal programming of health and disease of offspring in a sex-specific fashion.

Maternal exposure to organophosphate flame retardants and neonatal anthropometric measures

BACKGROUND

Organophosphate flame retardants (OPFRs) are widely used as flame retardants and plasticizers. Laboratory evidence has suggested that maternal OPFR exposure may adversely affect fetal growth, but the epidemiological data are limited.

OBJECTIVES

To investigate the association of maternal OPFR exposure with neonatal anthropometric measures.

METHODS

This study included 354 mother-newborn pairs from the Laizhou Wan Birth Cohort (LWBC), China. Ten OPFR metabolites were measured in maternal urine samples collected before delivery. Neonatal anthropometric data was collected from medical records and standardized into z-scores using the WHO standards (2007), including the weight-for-age (WAZ), length-for-age (LAZ), body mass index-for-age (BMIZ), weight-for-length (WLZ), and head circumference-for-age z-score (HCZ). Multiple linear regression and weighted quantile sum (WQS) regression were used to estimate the associations of individual OPFR metabolites and their mixtures with neonatal anthropometrics, respectively. Stratified analysis by sex was performed.

RESULTS

The detection rates of BCEP, DPHP, BCIPP, BDCIPP, BBOEP, DnBP and DiBP were above 60%, with median concentrations ranging from 0.14 to 3.60 μg/g creatinine. Most OPFR metabolites (i.e., BCIPP, BDCIPP, DiBP, DnBP, or BBOEP) were associated with decreased offspring WAZ and HCZ. When using WQS analysis, the OPFR metabolite mixture was inversely associated with the WAZ, BMIZ and HCZ, whereas DnBP had the highest weights. After stratified by gender, the negative associations were more pronounced among males.

CONCLUSIONS

Maternal OPFR exposure was negatively associated with offspring WAZ, BMIZ, and HCZ, and males seemed to be more vulnerable to the developmental toxicity of certain OPFRs.

Associations of Maternal Serum Iodine Concentration with Obstetric Complications and Birth Outcomes-Longitudinal Analysis Based on the Huizhou Mother-Infant Cohort, South China

This study aimed to explore the temporal associations between maternal serum iodine concentration (SIC) and common pregnancy outcomes in Chinese women. Eligible singleton pregnant women aged 20-34 years were selected, and their fasting blood samples were collected during early (T1, n = 1101) and mid-pregnancy (T2, n = 403) for SIC testing by inductively coupled plasma mass spectrometry. Multivariable linear regression indicated that log₁₀SIC at T1 (β = -0.082), T2 (β = -0.198), and their % change (β = -0.131) were inversely associated with gestational weight gain (GWG, all p < 0.05). Maternal log₁₀SIC at both T1 (β = 0.077) and T2 (β = 0.105) were positively associated with the Apgar score at 1 min (both p < 0.05). Women in the third quartile (Q3) of SIC at T1 had a lower risk of small for gestational age (SGA, OR = 0.405, 95% CI: 0.198-0.829) compared with those in Q4. Restricted cubic spline regression suggested a U-shaped association between SIC and SGA risk, and SIC above 94 μg/L at T1 was the starting point for an increased risk of SGA. The risk of premature rupture of membrane (PROM) increased by 96% (OR = 1.960, 95% CI: 1.010-3.804) in Q4 compared to that in Q1. Our longitudinal data from an iodine-replete region of China indicated that high maternal SIC could restrict GWG and improve Apgar scores at delivery, but might increase the risk of SGA and PROM.

Attenuating effects of selenium and zinc against hexavalent chromium-induced oxidative stress, hormonal instability, and placenta damage in preimplanted rats

As a toxic metal, hexavalent chromium (CrVI) has effects on both the reproductive and endocrine systems. This study aimed to evaluate the protective effects of selenium (Se) and zinc (Zn) against the toxicity of chromium on the placenta in pregnant Wistar albino rats. Thirty pregnant Wistar rats were divided into control and four treated groups, receiving subcutaneously (s.c) on the 3rd day of pregnancy, K₂Cr₂O₇ (10 mg/kg body weight (bw)) alone, or in association with Se (0.3 mg/kg bw), ZnCl₂ (20 mg/kg bw), or both of them simultaneously. Plasma steroid hormones, placenta histoarchitecture, oxidative stress profile, and developmental parameters were investigated. These results showed that K₂Cr₂O₇ exposure induced a significant increase in the levels of both plasma estradiol (E₂) and placenta malondialdehyde (MDA), the number of fetal resorptions, and percent of post-implantation loss. On the other hand, K₂Cr₂O₇ significantly reduced developmental parameters, maternal body and placenta weight, and plasma progesterone (P) and chorionic gonadotropin hormone (β HCG) levels. However, K₂Cr₂O₇ significantly decreased the placenta activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), and nonprotein sulfhydryl (NPSH). These changes have been reinforced by histopathological evaluation of the placenta. Se and/or ZnCl₂ supplementation provoked a significant improvement in most indices. These results suggest that the co-treatment with Se or ZnCl₂ strongly opposes the placenta cytotoxicity induced by K₂Cr₂O₇ through its antioxidant action.

A change of heart: understanding the mechanisms regulating cardiac proliferation and metabolism before and after birth

Mammalian cardiomyocytes undergo major maturational changes in preparation for birth and postnatal life. Immature cardiomyocytes contribute to cardiac growth via proliferation and thus the heart has the capacity to regenerate. To prepare for postnatal life, structural and metabolic changes associated with increased cardiac output and function must occur. This includes exit from the cell cycle, hypertrophic growth, mitochondrial maturation and sarcomeric protein isoform switching. However, these changes come at a price: the loss of cardiac regenerative capacity such that damage to the heart in postnatal life is permanent. This is a significant barrier to the development of new treatments for cardiac repair and contributes to heart failure. The transitional period of cardiomyocyte growth is a complex and multifaceted event. In this review, we focus on studies that have investigated this critical transition period as well as novel factors that may regulate and drive this process. We also discuss the potential use of new biomarkers for the detection of myocardial infarction and, in the broader sense, cardiovascular disease.

Long read isoform sequencing reveals hidden transcriptional complexity between cattle subspecies

The Iso-Seq method of full-length cDNA sequencing is suitable to quantify differentially expressed genes (DEGs), transcripts (DETs) and transcript usage (DTU). However, the higher cost of Iso-Seq relative to RNA-seq has limited the comparison of both methods. Transcript abundance estimated by RNA-seq and deep Iso-Seq data for fetal liver from two cattle subspecies were compared to evaluate concordance. Inter-sample correlation of gene- and transcript-level abundance was higher within technology than between technologies. Identification of DEGs between the cattle subspecies depended on sequencing method with only 44 genes identified by both that included 6 novel genes annotated by Iso-Seq. There was a pronounced difference between Iso-Seq and RNA-seq results at transcript-level wherein Iso-Seq revealed several magnitudes more transcript abundance and usage differences between subspecies. Factors influencing DEG identification included size selection during Iso-Seq library preparation, average transcript abundance, multi-mapping of RNA-seq reads to the reference genome, and overlapping coordinates of genes. Some DEGs called by RNA-seq alone appear to be sequence duplication artifacts. Among the 44 DEGs identified by both technologies some play a role in immune system, thyroid function and cell growth. Iso-Seq revealed hidden transcriptional complexity in DEGs, DETs and DTU genes between cattle subspecies previously missed by RNA-seq.

Evaluation of Clinical and Biochemical Traits in Egyptian Barki Sheep with Different Growth Performances

The Barki sheep industry is becoming increasingly important in Egypt because of the high quality of their meat and wool. This sheep breed is also commonly known for its resistance to arid and harsh environmental conditions. Such characteristics can be exploited in solving the problematic situation of inadequate animal protein for human consumption, particularly under climatic changes. However, very few studies have investigated aspects of breeding, nutrition, and susceptibility to infectious or non-infectious diseases in Barki sheep. Herein, we propose to unravel the differences in the clinical and biochemical profiles among Barki sheep of different growth rates. We measured clinical and biochemical parameters in stunted (n = 10; test group) and in good body condition (n = 9; control group) Barki sheep. Animals subjected to this experiment were of the same sex (female), age (12 months old), and housed in the same farm with similar conditions of feeding, management practice, and vaccination and deworming regimens. Regarding clinical examination, stunted/tested sheep showed a significantly higher pulse and respiratory rate compared to sheep with a good body condition/control group. The appetite, body temperature, and digestion processes were the same in both groups. In biochemical investigations, nutritional biomarkers were reduced markedly in stunted sheep compared with the control sheep, including total protein (p = 0.0445), albumin (p = 0.0087), cholesterol (p = 0.0007), and triglycerides (p = 0.0059). In addition, the Barki sheep test group suffered from higher levels of urea and blood urea nitrogen than the control group. Consistently, growth and thyroid hormone levels were lower in stunted sheep than the control sheep, although the differences were not statistically significant (p > 0.05). No significant differences were detected in both groups for serum levels of calcium, phosphorus, magnesium, iron, and zinc (p > 0.05). To detect the reasons for emaciation, certain debilitating infections were tested. All tested sheep showed negative coprological tests for gastrointestinal parasites, and had no obvious seropositivity to brucellosis, toxoplasmosis, neosporosis, or Q fever. This study demonstrates the useful biochemical markers for monitoring growth performance in Egyptian Barki sheep and unravels the usefulness of this breed in nationwide breeding and farming.

Hypothyroidism impairs development of the gastrointestinal tract in the ovine fetus

Growth and maturation of the fetal gastrointestinal tract near term prepares the offspring for the onset of enteral nutrition at birth. Structural and functional changes are regulated by the prepartum rise in cortisol in the fetal circulation, although the role of the coincident rise in plasma tri-iodothyronine (T3) is unknown. This study examined the effect of hypothyroidism on the structural development of the gastrointestinal tract and the activity of brush-border digestive enzymes in the ovine fetus near term. In intact fetuses studied between 100 and 144 days of gestation (dGA; term ∼145 days), plasma concentrations of T3, cortisol and gastrin; the mucosal thickness in the abomasum, duodenum, jejunum and ileum; and intestinal villus height and crypt depth increased with gestational age. Removal of the fetal thyroid gland at 105-110 dGA suppressed plasma thyroxine (T4) and T3 concentrations to the limit of assay detection in fetuses studied at 130 and 144 dGA, and decreased plasma cortisol and gastrin near term, compared to age-matched intact fetuses. Hypothyroidism was associated with reductions in the relative weights of the stomach compartments and small intestines, the outer perimeter of the intestines, the thickness of the gastric and intestinal mucosa, villus height and width, and crypt depth. The thickness of the mucosal epithelial cell layer and muscularis propria in the small intestines were not affected by gestational age or treatment. Activities of the brush border enzymes varied with gestational age in a manner that depended on the enzyme and region of the small intestines studied. In the ileum, maltase and dipeptidyl peptidase IV (DPPIV) activities were lower, and aminopeptidase N (ApN) were higher, in the hypothyroid compared to intact fetuses near term. These findings highlight the importance of thyroid hormones in the structural and functional development of the gastrointestinal tract near term, and indicate how hypothyroidism in utero may impair the transition to enteral nutrition and increase the risk of gastrointestinal disorders in the neonate.

Free thyroxine measurement in clinical practice: how to optimize indications, analytical procedures, and interpretation criteria while waiting for global standardization

Thyroid dysfunctions are among the most common endocrine disorders and accurate biochemical testing is needed to confirm or rule out a diagnosis. Notably, true hyperthyroidism and hypothyroidism in the setting of a normal thyroid-stimulating hormone level are highly unlikely, making the assessment of free thyroxine (FT4) inappropriate in most new cases. However, FT4 measurement is integral in both the diagnosis and management of relevant central dysfunctions (central hypothyroidism and central hyperthyroidism) as well as for monitoring therapy in hyperthyroid patients treated with anti-thyroid drugs or radioiodine. In such settings, accurate FT4 quantification is required. Global standardization will improve the comparability of the results across laboratories and allow the development of common clinical decision limits in evidence-based guidelines. The International Federation of Clinical Chemistry and Laboratory Medicine Committee for Standardization of Thyroid Function Tests has undertaken FT4 immunoassay method comparison and recalibration studies and developed a reference measurement procedure that is currently being validated. However, technical and implementation challenges, including the establishment of different clinical decision limits for distinct patient groups, still remain. Accordingly, different assays and reference values cannot be interchanged. Two-way communication between the laboratory and clinical specialists is pivotal to properly select a reliable FT4 assay, establish reference intervals, investigate discordant results, and monitor the analytical and clinical performance of the method over time.

Genome wide association study of thyroid hormone levels following challenge with porcine reproductive and respiratory syndrome virus

Introduction: Porcine reproductive and respiratory syndrome virus (PRRSV) causes respiratory disease in piglets and reproductive disease in sows. Piglet and fetal serum thyroid hormone (i.e., T3 and T4) levels decrease rapidly in response to Porcine reproductive and respiratory syndrome virus infection. However, the genetic control of T3 and T4 levels during infection is not completely understood. Our objective was to estimate genetic parameters and identify quantitative trait loci (QTL) for absolute T3 and/or T4 levels of piglets and fetuses challenged with Porcine reproductive and respiratory syndrome virus. Methods: Sera from 5-week-old pigs (N = 1792) at 11 days post inoculation (DPI) with Porcine reproductive and respiratory syndrome virus were assayed for T3 levels (piglet_T3). Sera from fetuses (N = 1,267) at 12 or 21 days post maternal inoculation (DPMI) with Porcine reproductive and respiratory syndrome virus of sows (N = 145) in late gestation were assayed for T3 (fetal_T3) and T4 (fetal_T4) levels. Animals were genotyped using 60 K Illumina or 650 K Affymetrix single nucleotide polymorphism (SNP) panels. Heritabilities, phenotypic correlations, and genetic correlations were estimated using ASREML; genome wide association studies were performed for each trait separately using Julia for Whole-genome Analysis Software (JWAS). Results: All three traits were low to moderately heritable (10%-16%). Phenotypic and genetic correlations of piglet_T3 levels with weight gain (0-42 DPI) were 0.26 ± 0.03 and 0.67 ± 0.14, respectively. Nine significant quantitative trait loci were identified for piglet_T3, on Sus scrofa chromosomes (SSC) 3, 4, 5, 6, 7, 14, 15, and 17, and collectively explaining 30% of the genetic variation (GV), with the largest quantitative trait loci identified on SSC5, explaining 15% of the genetic variation. Three significant quantitative trait loci were identified for fetal_T3 on SSC1 and SSC4, which collectively explained 10% of the genetic variation. Five significant quantitative trait loci were identified for fetal_T4 on SSC1, 6, 10, 13, and 15, which collectively explained 14% of the genetic variation. Several putative immune-related candidate genes were identified, including CD247, IRF8, and MAPK8. Discussion: Thyroid hormone levels following Porcine reproductive and respiratory syndrome virus infection were heritable and had positive genetic correlations with growth rate. Multiple quantitative trait loci with moderate effects were identified for T3 and T4 levels during challenge with Porcine reproductive and respiratory syndrome virus and candidate genes were identified, including several immune-related genes. These results advance our understanding of growth effects of both piglet and fetal response to Porcine reproductive and respiratory syndrome virus infection, revealing factors associated with genomic control of host resilience.

Developmental programming of mitochondrial substrate metabolism in skeletal muscle of adult sheep by cortisol exposure before birth

Prenatal glucocorticoid overexposure causes adult metabolic dysfunction in several species but its effects on adult mitochondrial function remain largely unknown. Using respirometry, this study examined mitochondrial substrate metabolism of fetal and adult ovine biceps femoris (BF) and semitendinosus (ST) muscles after cortisol infusion before birth. Physiological increases in fetal cortisol concentrations pre-term induced muscle- and substrate-specific changes in mitochondrial oxidative phosphorylation capacity in adulthood. These changes were accompanied by muscle-specific alterations in protein content, fibre composition and abundance of the mitochondrial electron transfer system (ETS) complexes. In adult ST, respiration using palmitoyl-carnitine and malate was increased after fetal cortisol treatment but not with other substrate combinations. There were also significant increases in protein content and reductions in the abundance of all four ETS complexes, but not ATP synthase, in the ST of adults receiving cortisol prenatally. In adult BF, intrauterine cortisol treatment had no effect on protein content, respiratory rates, ETS complex abundances or ATP synthase. Activity of citrate synthase, a marker of mitochondrial content, was unaffected by intrauterine treatment in both adult muscles. In the ST but not BF, respiratory rates using all substrate combinations were significantly lower in the adults than fetuses, predominantly in the saline-infused controls. The ontogenic and cortisol-induced changes in mitochondrial function were, therefore, more pronounced in the ST than BF muscle. Collectively, the results show that fetal cortisol overexposure programmes mitochondrial substrate metabolism in specific adult muscles with potential consequences for adult metabolism and energetics.

Stress-Sensitive Regulators of Fetal Neurodevelopment in HIV and Preeclampsia: An Immunocytochemical Appraisal of Placental OGT and T4 Levels

Preeclampsia and HIV are a significant burden to maternal health globally, especially in low-middle income countries such as South Africa. In the KwaZulu-Natal province, SA antenatal HIV prevalence is 41.1%, while PE is 12%. PE and HIV infections are maternal stress and inflammation that impact placental function and fetal development. Therefore, this study investigated the impact of the comorbidity of PE and HIV on placental stress and neurodevelopment. Placentae were obtained from four cohorts of pregnant women: normotensive HIV negative, normotensive HIV positive, preeclamptic HIV negative, and preeclamptic HIV positive. The placental tissue sections were immunostained for OGT and T4. Our findings showed that the maternal weight, diastolic, and systolic blood pressures (BP) were higher in PE vs. the normotensive groups, irrespective of HIV status. In addition, significant changes were noticed in the placental weight, fetoplacental ratio, and placental efficiency coefficient. Our findings showed that the maternal weight, diastolic, and systolic blood pressures (BP) were statistically higher in the PE compared to the normotensive. No significant differences were observed between HIV positive and HIV negative groups. In addition, significant changes were noticed in the placental weight, fetoplacental ratio, and placental coefficient. Furthermore, considerable upregulation in the placental expression of OGT in both the conducting and exchange villi of PE and concomitant downregulation in HIV-positive patients compared with Normotensive and HIV-negative individuals, respectively. Our results provide inferential evidence on the dysregulation of OGT in the comorbidity of PE and HIV. This may mediate a compromised programmed outcome of an adverse maternal environment during pregnancy and consequently affect fetal development.

Thyroid hormones and carnitine in the second trimester negatively affect neonate birth weight: A prospective cohort study

BACKGROUND

Maternal thyroid hormones and carnitine are reported to affect neonate birth weight during the second trimester, which is one of the most important markers for fetal growth and perinatal mortality and morbidity. Nevertheless, the effect of thyroid hormone and carnitine in the second trimester on birth weight has yet to be understood.

METHOD

This was a prospective cohort study with 844 subjects enrolled during the first trimester. Thyroid hormones, free carnitine (C0), neonate birth weight, as well as other related clinical and metabolic data were collected and assessed.

RESULTS

Pre-pregnancy weight and body mass index (BMI) as well as neonate birth weight were significantly different among different free thyroxine (FT4) level groups. Maternal weight gain and neonate birth weight varied significantly when grouped by different thyroid-stimulating hormone (TSH) levels. There was a significantly positive correlation between C0 and TSH (r = 0.31), free triiodothyronine (FT3) (r = 0.37), and FT4 (r = 0.59) (all P < 0.001). In addition, a significantly negative influence was found between birth weight and TSH (r = -0.48, P = 0.028), so as C0 (r = -0.55, P < 0.001) and FT4 (r = -0.64, P < 0.001). Further assessment detected a stronger combined effect of C0 and FT4 (P < 0.001) and of C0 and FT3 (P = 0.022) on birth weight.

CONCLUSION

Maternal C0 and thyroid hormones are of great importance in neonate birth weight, and routine examination of C0 and thyroid hormones during the second trimester has a positive effect on the intervention of birth weight.

Prenatal exposure to polybrominated diphenyl ethers and birth outcomes

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) were used as flame retardants and from their end-use products they can be released to accumulate within indoor environments. This may result in exposures to pregnant women with potential adverse effects on the developing fetus. While studies have shown associations between prenatal PBDE exposure and poor birth outcomes, research has mainly focused on birth weight and gestational age and may miss important indicators of newborn size.

METHODS

The sample included a cohort of Dominican and African American mother-child pairs from New York City recruited from 1998 to 2006. PBDE congeners (BDE-47, BDE-99, BDE-100, and BDE-153) were measured in cord serum at birth and dichotomized into low (<80th percentile) and high (>80th percentile) categories. Weight, length, head circumference, and gestational age were measured at birth and the ponderal index (birth weight/length x 100), size for gestational age, and population-based z-scores were calculated (n = 305). Separate regression analyses were conducted to estimate associations between PBDEs or PBDE sum (ng/g lipid) and birth outcomes. Quantile g-computation was performed to estimate the effect of total PBDE mixture. We also assessed effect modification by sex and ethnicity.

RESULTS

Adjusting for relevant covariates, the high exposure category of BDE-153 was associated with lower birth weight z-score (-0.25, 95% CI: -0.5, 0.0) and longer gestation (0.43 weeks, 95% CI: 0.07, 0.79). The high exposure category of BDE-99 was associated with lower birth length z-score (-0.55, 95% CI: -0.98, -0.12). There was a negative association between the overall PBDE mixture and birth length z-score (-0.10, 95% CI: -0.21, 0.00) per 1 quintile increase in PBDEs. There was no effect modification by sex or ethnicity.

CONCLUSIONS

These results suggest that prenatal exposures to BDE-153, BDE-99, and total PBDE mixture are associated with birth outcomes in a cohort of Dominican and African American newborns.

Developmental changes of the fetal and neonatal thyroid gland and functional consequences on the cardiovascular system

Thyroid hormones play an important role in the development and function of the cardiac myocyte. Dysregulation of the thyroid hormone milieu affects the fetal cardiac cells via complex molecular mechanisms, either by altering gene expression or directly by affecting post-translational processes. This review offers a comprehensive summary of the effects of thyroid hormones on the developing cardiovascular system and its adaptation. Furthermore, we will highlight the gaps in knowledge and provide suggestions for future research.

Thyroid hormones: Metabolism and transportation in the fetoplacental unit

The thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3), are of vital importance for fetal development. The concentration of THs in fetal circulation varies throughout gestation and differs from the concentration in the maternal serum, indicating the presence of maternal-fetal thyroid homeostasis regulatory mechanisms in the placenta. The passage of THs from maternal circulation to fetal circulation is modulated by plasma membrane transporters, enzymes, and carrier proteins. Monocarboxylate transporter 8, iodothyronine deiodinases (DIO2 and DIO3), and transthyretin are especially involved in this maternal-fetal thyroid modulation, shown by a greater expression in the placenta. THs also play a role in placental development and as expected, abnormal variations in TH levels are associated with pregnancy complications and can result in damage to the fetus. Although new evidence regarding TH regulation during pregnancy and its effects in the mother, placenta, and fetus has been published, many aspects of these interactions are still poorly understood. The objective of this review is to provide an evidence-based update, drawn from current data, on the metabolism and transport of THs in the placenta and their vital role in the maternal-fetal relationship.

Association of exposure to ambient particulate matter with maternal thyroid function in early pregnancy

BACKGROUND

It is known that maternal thyroid dysfunction during early pregnancy can cause adverse pregnancy complications and birth outcomes. This study was designed to examine the association between ambient particulate matter with aerodynamic diameters ≤2.5 μm (PM2.5) and particulate matter with aerodynamic diameters ≤10 μm (PM10) exposure and maternal thyroid function during early pregnancy.

METHODS

This study was based on data from a birth cohort study of 921 pregnant women in China. We estimated associations between ambient PM2.5 and PM10 exposure during the first trimester of pregnancy (estimated with land-use regression models) and maternal thyroid hormone concentrations (free thyroxine (FT4), free tri-iodothyronine (FT3), and thyroid-stimulating hormone (TSH)) collected between weeks 10 and 17 of gestation using linear regression models adjusting for potential confounders. Ambient PM2.5 and PM10 concentrations were modeled per interquartile range (IQR) increment and as tertiles based on the distribution of the exposure levels.

RESULTS

An IQR increment (68 μg/m3) in PM2.5 exposure was associated with a significant decrease in maternal FT4 levels (β = -0.60, 95% CI: -1.07, -0.12); and a significant decrease in FT4/FT3 ratio (β = -0.13, 95% CI: -0.25, -0.02). Further analyses showed that, relative to the lowest tertile, women in both the middle and highest tertiles of PM2.5 had significantly lower concentrations of maternal FT4 and FT4/FT3 ratio. No significant associations were found between PM2.5 and FT3 or TSH levels. PM10 exposure was not significantly associated with maternal thyroid function.

CONCLUSIONS

Our study suggested that higher ambient PM2.5, not PM10, exposed during the first trimester of pregnancy were associated with a significant decrease in maternal serum FT4 concentrations and FT4/FT3 ratio. Studies in populations with different exposure levels are needed to replicate our study results.

Phenol and Phthalate Effects on Thyroid Hormone Levels during Pregnancy: Relying on In Vitro Assays and Adverse Outcome Pathways to Inform an Epidemiological Analysis

BACKGROUND

Studies characterizing associations between phenols, phthalates and thyroid hormones during pregnancy produce inconsistent results. This divergence may be partly attributable to false positives due to multiple comparison testing of large numbers of chemicals, and measurement error as studies rely on small numbers of biospecimens despite high intra-individual variability in urinary chemical metabolite concentrations.

OBJECTIVES

This study employs a priori chemical filtering and expanded urinary biomonitoring to evaluate associations between phenol/phthalate exposures and serum thyroid hormones assessed during pregnancy.

METHODS

A two-tiered approach was implemented: a) In vitro high-throughput screening results from the ToxCast/Tox21 database, as informed by a thyroid Adverse Outcome Pathway network, were evaluated to select phenols/phthalates with activity on known and putative molecular initiating events in the thyroid pathway; and b) Adjusted linear regressions were used to study associations between filtered compounds and serum thyroid hormones measured in 437 pregnant women recruited in Grenoble area (France) between 2014 and 2017. Phenol/phthalate metabolites were measured in repeated spot urine sample pools (median: 21 samples/women).

RESULTS

The ToxCast/Tox21 screening reduced the chemical set from 16 to 13 and the associated number of statistical comparisons by 19%. Parabens were negatively associated with free triiodothyronine (T3) and the T3/T4 (total thyroxine) ratio. Monobenzyl phthalate was positively associated with total T4 and negatively with the T3/T4 ratio. Effect modification by iodine status was detected for several compounds (among them ΣDEHP and mono-n-butyl phthalate) that were associated with some hormones among women with normal iodine levels.

CONCLUSION

For these chemicals, screening for compounds with an increased likelihood for thyroid-related effects and relying on repeated urine samples to assess exposures improved the overall performance of multichemical analyses of thyroid disruption. This approach may improve future evaluations of human data for the thyroid pathway with implication for fetal health and may serve as a model for evaluating other toxicity outcomes. https://doi.org/10.1289/EHP10239.

Association of maternal urinary fluoride concentrations during pregnancy with size at birth and the potential mediation effect by maternal thyroid hormones: The Swedish NICE birth cohort

BACKGROUND

Observational studies have indicated that elevated maternal fluoride exposure during pregnancy may impair child neurodevelopment but a potential impact on birth outcomes is understudied.

OBJECTIVES

To evaluate the impact of gestational fluoride exposure on birth outcomes (birth size and gestational age at birth) and to assess the potential mediating role of maternal thyroid hormones.

METHODS

We studied 583 mother-child dyads in the NICE cohort in northern Sweden. Maternal fluoride exposure was assessed by measuring urinary concentrations at late pregnancy (median: 29th gestational week) using an ion selective electrode. Plasma levels of free and total thyroxine (fT4, tT4) and triiodothyronine (fT3, tT3), and thyroid stimulating hormone (TSH) were measured with electrochemiluminescence immunoassays. The infant's weight, length, head circumference, and gestational age at birth were extracted from hospital records.

RESULTS

Median urinary fluoride concentration was 0.71 mg/L (5th-95th percentile 0.31-1.9 mg/L; specific gravity adjusted). In multivariable-adjusted regression models, every 1 mg/L increase of maternal urinary fluoride was associated with a mean increase in birth weight by 84 g (95%CI: 30, 138), length by 0.41 cm (95%CI: 0.18, 0.65), head circumference by 0.3 cm (95%CI: 0.1, 0.4), and with increased odds of being born large for gestational age (OR = 1.39, 95%CI: 1.03, 1.89). Every 1 mg/L increase of maternal urinary fluoride was also associated with a mean increase of the plasma fT3:fT4 ratio (B = 0.007, 95%CI: 0.000, 0.014), but not with the hormones or TSH. In mediation analyses, the maternal fT3:fT4 ratio did not explain the urinary fluoride-birth size relationships.

DISCUSSION

Gestational urinary fluoride concentrations were associated with increased size at birth and even with increased odds of being born large for gestational age. The fluoride-related associations with increased size at birth were not explained by changes in maternal thyroid hormone levels.

Maternal hypothyroidism is associated with M-opsin developmental delay

Thyroid hormones are critical for the development of opsins involved in color vision. Hypothyroid mice show delayed M-opsin development and expanded distribution of S-opsin on the retina. However, the effects of maternal hypothyroidism on opsin development remain unknown. This study investigates the effects of congenital central hypothyroidism and maternal hypothyroidism on opsin development in thyrotropin-releasing hormone knockout (TRH-/-) mice. We examined the mRNA expression and protein distribution of S/M-opsin on postnatal days (P)12 and 17, as well as mRNA expression of type 2 and 3 iodothyronine deiodinase (DIO2 and DIO3, respectively) in the retina and type 1 iodothyronine deiodinase (DIO1) in the liver at P12 in TRH+/- mice born to TRH+/- or TRH-/- dams, and conducted S/M-opsin analysis in TRH+/+ or TRH-/- mice born to TRH+/- dams at P12, P17, and P30. M-opsin expression was lower in TRH+/- mice born to TRH-/- dams than in those born to TRH+/- dams, whereas S-opsin expression did not significantly differ between them. DIO1, DIO2, and DIO3 mRNA expression levels were not significantly different between the two groups; therefore, thyroid function in peripheral tissues in the pups was similar. S/M-opsin expression did not significantly differ between the TRH+/+ and TRH-/- mice born to TRH+/- dams on any postnatal day. These results demonstrate that maternal hypothyroidism causes M-opsin developmental delay during the early developmental stages of neonatal mice, and TRH-/- mice, a model of congenital central hypothyroidism, born to a euthyroid dam do not have delayed opsin development.

Filtered air intervention modulates hypothalamic-pituitary-thyroid/gonadal axes by attenuating inflammatory responses in adult rats after fine particulate matter (PM2.5) exposure

We have previously reported that filtered air (FA) intervention reduces inflammation and hypothalamus-pituitary-adrenal axis activation after fine particulate matter (PM2.5 exposure). Whether FA also modulates the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes in rats after PM2.5 exposure is still unknown. Adult Sprague-Dawley rats were exposed to PM2.5 by using a "real-world" PM2.5 exposure system, and the FA intervention was conducted by renewing for 15 days. PM2.5 inhalation decreased thyrotropin-releasing hormone (TRH) and thyroxine (T4) levels in both male and female rats, and thyroid-stimulating hormone (TSH) level in male rats. FA intervention attenuated the reduction in TRH and TSH levels in male rats and reduction in T4 level in female rats. PM2.5 inhalation also reduced testosterone (T) level in male rats, and estradiol (E2) and progesterone (PROG) levels in female rats, and these changes were attenuated after FA intervention. The FA intervention attenuated the decreases in CD8 T cells and T cells induced by PM2.5 inhalation in female rats only by flow cytometry analysis. In blood, FA interventions ameliorated IL-6 and IL-1β mRNA levels in both male and female rats after PM2.5 exposure. FA intervention restored the IL-4 and IL-10 levels in female rats after PM2.5 exposure. Moreover, FA intervention ameliorated the inflammatory responses induced by PM2.5 inhalation in the thyroid and gonads in both male and female rats. These data indicate that FA intervention exerted an effect on modulating the hormonal balance of the HPT and HPG axes, and this may be related to a reduction in the inflammatory responses in the thyroid and gonads of PM2.5-treated rats, respectively.

Effects of porcine reproductive and respiratory syndrome virus (PRRSV) on thyroid hormone metabolism in the late gestation fetus

Porcine reproductive and respiratory syndrome virus (PRRSV) in late gestation causes a profound suppression of circulating maternal and fetal thyroid hormone during a critical window of development. To understand this relationship, we evaluated thyroid hormone metabolism at the maternal-fetal interface and within fetal tissues, along with hormone metabolite levels in serum. Fetuses were classified using an established model based on viral load in serum and thymus, and preservation status, including uninfected (UNIF), high-viral load viable (HV-VIA), and high-viral load meconium-stained (HV-MEC), with additional controls from sham-inoculated gilts (CON). Expression of three iodothyronine deiodinases, five sulfotransferases, sulfatase, and two solute carriers known to transport thyroid hormone were evaluated in maternal endometrium and fetal placenta, liver, and kidney. Serum thyroxin (T4), reverse triiodothyronine (rT3), and diiodothyronine (T2) were evaluated via liquid chromatography tandem mass spectrometry. Significant changes in gene expression were observed in all four tissues, with the liver being the most severely impacted. We observed local and fetal specific regulation of maternal tissues through significant upregulation of DIO2 and DIO3 expression in the endometrium corresponding to infected but viable fetuses relative to uninfected and control fetuses. Expression levels of DIO2 and DIO3 were significantly higher in the resilient (HV-VIA) fetuses relative to the susceptible (HV-MEC) fetuses. A substantial decrease in serum T4 was confirmed, with no corresponding increase in rT3 or T2. Collectively, these results show that thyroid hormone metabolism is altered at the maternal-fetal interface and within the PRRSV infected fetus and is associated with fetal viability.