Thyroid-stimulating hormone receptor and thyroid hormone receptors are involved in human endometrial physiology

Effect of progestin on thyroid function in female Wistar rats

Introduction

To characterize the influence of female-specific hormones on women's thyroid function, the study investigated the influence of extra progestin from oral contraceptives on inducing thyroid dysfunction.

Methods

Sixty female Wistar rats were divided into six groups based on levonorgestrel or desogestrel administration as the main active agents: control, low (0.0039 mg*20-fold), medium (0.0039 mg*100-fold), high (0.0318 mg*100-fold) levonorgestrel (pure product); and low (0.0083 mg*20-fold) and high (0.0083 mg*100-fold) desogestrel (pure product). Progestin was administered by gavage every 4 days for 1 month. Statistical analysis was performed using one-way analysis of variance and the Kruskal-Wallis test.

Results

Following levonorgestrel gavage, serum free T4 and thyroidstimulating hormone levels were significantly lower in the experimental group than that in the control group (p=0.013 and 0.043). After desogestrel gavage, the serum free T4 and free T3 levels were lower in the experimental group than that in the control group (p=0.019 and 0.030). Thyroid hormone antibody concentrations were lower in rats administered levonorgestrel and desogestrel than that in control rats. Moreover, exposure to progestin upregulated the expression of the thyroid-stimulating hormone receptor and sodium iodide symporter in thyroid.

Discussion

Progestin stimulation enhanced the proliferation of follicular epithelial cells in rat thyroid tissues. Progestin exposure could cause thyroid dysfunction by upregulating the transcription of thyroid-stimulating hormone receptor and sodium iodide symporter in thyroid, thus inducing pathomorphological changes in rats' thyroid.

The effect of levothyroxine and prednisolone treatment on pregnancy in in vitro fertilization patients with positive thyroid autoantibodies

AIM

To investigate the effects of levothyroxine and prednisolone treatment, or in combination, on positive thyroid autoantibodies in infertile patients undergoing in vitro fertilization (IVF) therapy.

METHODS

This retrospective study included a total of 190 patients with positive thyroid autoantibodies (anti-T and anti-TPO) who underwent IVF treatment between January 2008 and March 2016. Patients were divided into four groups: group 1-levothyroxine group (n = 50), group 2-prednisolone group (n = 50), group 3-levothyroxine and prednisolone combination (n = 25), group 4-control group (n = 65). Anti-T and anti-TPO levels before IVF and at the time of embryo transfer (ET), b-hcg positivity, clinical and biochemical pregnancy, miscarriage rate, and live birth rate were compared among groups.

RESULTS

In levothyroxine-treated group, mean anti-TPO levels significantly decreased at the time of ET compared to before IVF treatment levels (p = 0.036). In group 3, mean anti-T and anti-TPO levels significantly decreased at the time of ET compared to levels before IVF treatment (p < 0.05). Patients who became pregnant in group 1, mean anti-T anti-TPO levels significantly decreased compared to before IVF treatment levels (p < 0.05). The biochemical pregnancy rate was significantly higher in group 2 (p = 0.03). Abortion rates were the highest in group 3, but no significant difference was found among groups. The group treated with levothyroxine had a significantly increased rate of live birth compared to the control group (p = 0.02).

CONCLUSIONS

Levothyroxine addition during IVF treatment of patients with positive thyroid antibodies in subclinical hypothyroidism increases the take-home baby pregnancy rate. Whether subclinical hypothyroidism or not in IVF treatment, levothyroxine is more effective than low-dose corticosteroids.

A new prognostic model for recurrent pregnancy loss: assessment of thyroid and thromboelastograph parameters

Objective

This study aimed to identify predictors associated with thyroid function and thromboelastograph (TEG) examination parameters and establish a nomogram for predicting the risk of subsequent pregnancy loss in recurrent pregnancy loss (RPL).

Methods

In this retrospective study, we analyzed the medical records of 575 RPL patients treated at Lanzhou University Second Hospital, China, between September 2020 and December 2022, as a training cohort. We also included 272 RPL patients from Ruian People's Hospital between January 2020 and July 2022 as external validation cohort. Predictors included pre-pregnancy thyroid function and TEG examination parameters. The study outcome was pregnancy loss before 24 weeks of gestation. Variable selection was performed using least absolute shrinkage and selection operator regression and stepwise regression analyses, and the prediction model was developed using multivariable logistic regression. The study evaluated the model's performance using the area under the curve (AUC), calibration curve, and decision curve analysis. Additionally, dynamic and static nomograms were constructed to provide a visual representation of the models.

Results

The predictors used to develop the model were body mass index, previous pregnancy losses, triiodothyronine, free thyroxine, thyroid stimulating hormone, lysis at 30 minutes, and estimated percent lysis which were determined by the multivariable logistic regression with the minimum Akaike information criterion of 605.1. The model demonstrated good discrimination with an AUC of 0.767 (95%CI 0.725-0.808), and the Hosmer-Lemeshow test indicated good fitness of the predicting variables with a P value of 0.491. Identically, external validation confirmed that the model exhibited good performance with an AUC of 0.738. Moreover, the clinical decision curve showed a positive net benefit in the prediction model. Meanwhile, the web version we created was easy to use. The risk stratification indicated that high-risk patients with a risk score >147.9 had a higher chance of pregnancy loss (OR=6.05, 95%CI 4.09-8.97).

Conclusions

This nomogram well-predicted the risk of future pregnancy loss in RPL and can be used by clinicians to identify high-risk patients and provide a reference for pregnancy management of RPL.

Levothyroxine for a high-normal TSH in unexplained infertility

OBJECTIVE

Unexplained infertility affects nearly one-third of infertile couples. Women with unexplained infertility are more likely to have a high-normal thyroid-stimulating hormone level (TSH: 2.5-5 mIU/L) compared to women with severe male factor infertility. Practice guidelines vary on whether treatment should be initiated for TSH levels >2.5 mIU/L in women attempting conception because the effects of treating a high-normal TSH level with levothyroxine are not known. We evaluated conception and live birth rates in women with unexplained infertility and high-normal TSH levels.

DESIGN, PATIENTS AND MEASUREMENTS

Retrospective study including 96 women evaluated for unexplained infertility at a large academic medical centre between 1 January 2000 and 30 June 2017 with high-normal TSH (TSH: 2.5-5 mIU/L and within the normal range of the assay) who were prescribed (n = 31) or not prescribed (n = 65) levothyroxine. Conception and live birth rates were assessed.

RESULTS

The conception rate in the levothyroxine group was 100% compared to 90% in the untreated group (p = .086 unadjusted; p < .05 adjusted for age; p = .370 adjusted for TSH; p = .287 adjusted for age and TSH). The live birth rate was lower in the levothyroxine group (63%) compared to the untreated group (84%) (p = .05 unadjusted; p = .094 adjusted for age; p = .035 adjusted for TSH; p = .057 adjusted for age and TSH).

CONCLUSIONS

Women with unexplained infertility and high-normal TSH levels treated with levothyroxine had a higher rate of conception but lower live birth rate compared to untreated women, with the limitation of a small sample size. These findings assert the need for prospective, randomized studies to determine whether treatment with levothyroxine in women with unexplained infertility and high-normal TSH is beneficial.

Thyroid dysfunction and female infertility. A comprehensive review

INTRODUCTION

Female infertility is defined as the inability to achieve pregnancy following one year of consistent, unprotected sexual intercourse. Among the various endocrine factors contributing to this complex issue, thyroid dysfunction assumes a pivotal and noteworthy role.

METHODS

A narrative review, encompassing 134 articles up to 2023, was conducted utilizing the PubMed/Medline, EMBASE, and Scielo databases. The primary focus of this review was to investigate the effects of thyroid dysfunction on female infertility.

RESULTS

Thyroid disorders exert a significant influence on folliculogenesis, fertilization, and implantation processes. Thyroid autoimmunity, although associated with diminished ovarian reserve, does not typically necessitate levothyroxine therapy. On the other hand, both subclinical and overt hypothyroidism often require levothyroxine treatment to enhance fertility and optimize obstetric outcomes. Hyperthyroidism warrants prompt intervention due to its heightened risk of miscarriage. Furthermore, thyroid dysfunction exerts notable effects on assisted reproductive technologies, underscoring the importance of achieving euthyroidism prior to ovarian stimulation.

CONCLUSION

Women presenting with thyroid dysfunction must undergo meticulous and individualized assessments since fertility outcomes, whether achieved through natural conception or assisted reproductive technologies, can be significantly influenced by thyroid-related factors.

The role of the thyroid in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine and metabolic disease in women of childbearing age and can cause metabolic disorder, infertility, and increased anxiety and depression; as a result, it can seriously affect the physical and mental health of fertile women. PCOS is a highly clinically heterogeneous disease with unclear etiology and pathogenesis, which increases the difficulty of treatment. The thyroid gland has complex regulatory effects on metabolism, reproduction, and emotion, and produces hormones that act on almost all cells of the human body. The clinical manifestations of PCOS are similar to some thyroid diseases. Furthermore, some thyroid diseases, such as subclinical hypothyroidism (SCH), not only increase the incidence rate of PCOS, but also exacerbate its associated metabolic abnormalities and reproductive disorders. Interestingly, PCOS also increases the incidence of some thyroid diseases. However, the role of the thyroid in PCOS remains unclear. This review is intended to thoroughly explore the critical role of the thyroid in PCOS by summarizing the comorbidity of PCOS and thyroid diseases and their combined role in metabolic disorders, related metabolic diseases, and reproductive disorders; and by analyzing the potential mechanism through which the thyroid influences the development and progression of PCOS and its symptoms. We hope this review will provide a valuable reference for the role of the thyroid in PCOS.

The Thyroid Hormone Axis and Female Reproduction

Thyroid function affects multiple sites of the female hypothalamic-pituitary gonadal (HPG) axis. Disruption of thyroid function has been linked to reproductive dysfunction in women and is associated with menstrual irregularity, infertility, poor pregnancy outcomes, and gynecological conditions such as premature ovarian insufficiency and polycystic ovarian syndrome. Thus, the complex molecular interplay between hormones involved in thyroid and reproductive functions is further compounded by the association of certain common autoimmune states with disorders of the thyroid and the HPG axes. Furthermore, in prepartum and intrapartum states, even relatively minor disruptions have been shown to adversely impact maternal and fetal outcomes, with some differences of opinion in the management of these conditions. In this review, we provide readers with a foundational understanding of the physiology and pathophysiology of thyroid hormone interactions with the female HPG axis. We also share clinical insights into the management of thyroid dysfunction in reproductive-aged women.

TSH levels after fresh embryo transfer are associated with reproductive outcomes in euthyroid women undergoing the first IVF/ICSI cycles

To investigate whether there is a relationship between TSH levels on the 14th day post embryo transfer (D14 TSH levels) and the reproductive outcomes in euthyroid women who are free from levothyroxine (LT4) treatment and undergo the first in vitro fertilization /intracytoplasmic sperm injection embryo transfer (IVF/ICSI-ET) cycles with the homogeneous ovarian stimulation protocols. This was a prospective study including a total of 599 euthyroid women undergoing the first IVF/ICSI ET cycles. Serum samples were collected and frozen on the 14th day post embryo transfer. TSH levels were measured after the confirmation of clinical pregnancy. The patients were divided into three groups (low-normal ≤ 2.5 mIU/L; high-normal 2.5-4.2 mIU/L; and high > 4.2 mIU/L) based on D14 TSH levels. Reproductive outcomes were compared among the three groups. Binary logistic regression analyses and generalized additive mixed models with smoothing splines were used to investigate the relationship between TSH levels and reproductive outcomes. D14 TSH levels were significantly elevated compared to basal TSH levels, and the degree of TSH elevation was significantly higher in pregnant women compared to that in non-pregnant women. The clinical pregnancy and live birth rates increased significantly in the high-normal D14 TSH groups, and doubled in the high D14 TSH groups compared to the low TSH groups. When adjusted by age, basal TSH, AMH, E2, endometrial thickness, type and causes of infertility, and transferred embryos, the dose-dependent relationships between D14 TSH and clinical pregnancy and live birth were observed. Obstetric outcomes in singleton or twins live birth among the different D14 TSH groups were similar. Elevated D14 TSH levels were associated with better clinical pregnancy and live birth rates, and were not associated with worse obstetric outcomes. The mechanisms to explain the phenomenon remained to be studied.

Is there an association between endometriosis and thyroid autoimmunity?

OBJECTIVE

It has been suggested that non-uterine endometrial implants can express thyroid-stimulating hormone receptors, thus inducing the formation of thyroid-stimulating immunoglobulin. We aimed to compare the autoantibody positivity in patients with and without endometriosis and to determine whether there is a difference in the incidence of thyroid diseases.

METHODS

This prospective observational study was conducted on 102 women who had been operated on for benign gynecological diseases. Cases enrolling in the study were divided into two groups: the study group with endometriosis (n=51) and the control group without endometriosis (n=51). The blood tests for thyroid-stimulating hormone, free thyroxine (fT4), thyroid-stimulating immunoglobulin, and anti-thyroid peroxidase antibody levels were checked.

RESULTS

The mean thyroid-stimulating immunoglobulin level was found to be higher in the endometriosis group than in the control group. However, this difference was not statistically significant. No significant difference was detected between endometriosis and control groups in terms of anti-thyroid peroxidase antibody and thyroid-stimulating hormone levels. The mean fT4 value (0.97±0.13 ng/dL) of the endometriosis patients was found to be significantly lower than the control group (1.08±0.21 ng/dL) (p=0.002; p<0.05). The mean anti-thyroid peroxidase antibody value of cases with bilateral endometrioma (82.21±252.29 IU/mL) was significantly higher than cases with unilateral endometrioma (15.81±83.13 IU/mL) (p=0.028; p<0.05). There is a positive and significant relationship between the size of endometriosis and anti-thyroid peroxidase antibody values (p=0.011; p<0.05).

CONCLUSION

This study points to an association between endometrioma diameter and anti-thyroid peroxidase antibody values which can be a stepping stone for new studies evaluating this hypothesis further.

Relationship between thyroid antibody levels and ovarian reserve function in infertile chinese women with normal thyroid-stimulating hormone

BACKGROUND

To analyze the relationship of thyroid peroxidase antibody and thyroid globulin antibody levels with ovarian reserve function in infertile women.

METHODS

The data of 721 infertile patients who visited the hospital from January 2019 to September 2022 and whose thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels were in the normal range, were retrospectively analyzed. These patients were divided into two sets of three groups-the negative group, the 2.6 IU/ml ~ 100 IU/ml group and the TPOAb > 100 IU/ml group according to the TPOAb (thyroid peroxidase antibody) level, or the TgAb (anti-thyroglobulin antibody) negative group, the 14.58 IU/ml ~ 100 IU/ml group and the TgAb > 100 IU/ml group according to the TgAb level. They were compared for differences in ovarian reserve function index and thyroid hormone levels and analyzed for the relationship among thyroid antibody levels, ovarian reserve function, and thyroid hormone levels.

RESULTS

When TSH > 2.5 mIU/L, the bFSH (basal follicle stimulating hormone) level in the TPOAb > 100 IU/ml group (9.10 ± 1.16 IU/L) was significantly higher than that in the TPOAb negative group (8.12 ± 1.97 IU/L) and the 2.6 IU/ml ~ 100 IU/ml group (7.90 ± 1.48 IU/L) (P < 0.05); when TSH ≤ 2.5 mIU/L, there were no statistically significant differences in the bFSH and AFC (antral follicle count) number at different TPOAb levels. Whether TSH ≤ 2.5 mIU/L or TSH > 2.5 mIU/L, there were no statistically significant differences in the bFSH and AFC number at different TgAb levels (P > 0.05). FT3/FT4 ratio in the TPOAb 2.6 IU/ml ~ 100 IU/ml group and the > 100 IU/ml group was significantly lower than in the negative group. FT3/FT4 ratio in the TgAb 14.58 ~ 100 IU/ml group and the > 100 IU/ml group was also significantly lower than in the TgAb negative group (P < 0.05). TSH level in the TPOAb > 100 IU/ml group was significantly higher than in the 2.6 ~ 100 IU/ml group and the TPOAb negative group, but there were no statistically significant differences among different TgAb groups.

CONCLUSIONS

When TPOAb > 100 IU/ml and TSH > 2.5 mIU/L, it may affect the ovarian reserve function in infertile patients, and the mechanism may be associated with increased TSH and the imbalance of FT3/FT4 ratio caused by the increase of TPOAb.

Female Papillary Thyroid Cancer Survivors Are at Increased Risk of Adenomyosis and Endometrial Hyperplasia

PURPOSE

Thyroid cancer (TC) is the most common endocrine cancer worldwide, affecting mainly women of reproductive age. However, no data exist about its association with endometrial or uterine disorders. This study aimed to assess the risk of hyperproliferative pathology of the reproductive system in female ТС survivors.

METHODS

This was a cross-sectional study of female patients aged 20-45 years diagnosed with papillary TC (PTC) from 1994-2018. Age-matched females with normal thyroid structures served as controls.

RESULTS

One hundred and sixteen patients (mean age 36.7±61 years) and 90 age-matched controls were included. PTC survivors demonstrated an increased risk for adenomyosis [odds ratio (OR) 2.5, 95% confidence interval (CI) 1.3-4.8] and endometrial hyperplasia (OR 3.9, 95% CI 1.1-14.3), compared with controls. The risk for adenomyosis was higher after the ten post-operative years (OR 5.3, 95% CI 2.29- 12.05) than during the first 5-10 years (OR 2.3, 95% CI 1.02-5.10) and increased with the number of RAI courses and the degree of TSH suppression. The risk of endometrial hyperplasia was most evident during the first five years post-thyroidectomy (OR 6.0, 95% CI 1.4-25.5), especially in patients with TSH <0.1 mU/L (OR 6.8, 95% CI 1.4-33.28) No difference in uterine leiomyomas or endometrial polyps was found between PTC survivors and controls.

CONCLUSIONS

Female PTC survivors are at increased risk of endometrial hyperplasia and adenomyosis compared with those with normal thyroid structures.

Periconceptional biomarkers for maternal obesity: a systematic review

Periconceptional maternal obesity is linked to adverse maternal and neonatal outcomes. Identifying periconceptional biomarkers of pathways affected by maternal obesity can unravel pathophysiologic mechanisms and identify individuals at risk of adverse clinical outcomes. The literature was systematically reviewed to identify periconceptional biomarkers of the endocrine, inflammatory and one-carbon metabolic pathways influenced by maternal obesity. A search was conducted in Embase, Ovid Medline All, Web of Science Core Collection and Cochrane Central Register of Controlled Trials databases, complemented by manual search in PubMed until December 31^st, 2020. Eligible studies were those that measured biomarker(s) in relation to maternal obesity, overweight/obesity or body mass index (BMI) during the periconceptional period (14 weeks preconception until 14 weeks post conception). The ErasmusAGE score was used to assess the quality of included studies. Fifty-one articles were included that evaluated over 40 biomarkers. Endocrine biomarkers associated with maternal obesity included leptin, insulin, thyroid stimulating hormone, adiponectin, progesterone, free T4 and human chorionic gonadotropin. C-reactive protein was associated with obesity as part of the inflammatory pathway, while the associated one-carbon metabolism biomarkers were folate and vitamin B12. BMI was positively associated with leptin, C-reactive protein and insulin resistance, and negatively associated with Free T4, progesterone and human chorionic gonadotropin. Concerning the remaining studied biomarkers, strong conclusions could not be established due to limited or contradictory data. Future research should focus on determining the predictive value of the optimal set of biomarkers for their use in clinical settings. The most promising biomarkers include leptin, adiponectin, human chorionic gonadotropin, insulin, progesterone and CRP.

Impact of photoperiod on uterine redox/inflammatory and metabolic status of golden hamster, Mesocricetus auratus

Photoperiod modulates reproductive physiology at multiple levels in seasonally breeding animals. Golden hamsters are long-day breeders that diminish their fertility during the short days. Photoperiod is known to regulate hormonal milieu and uterus is a hormone-sensitive dynamic tissue. However, there is lack of molecular insight regarding the impact of photoperiod on uterine physiology with respect to redox and metabolic status in Mesocricetus auratus. We evaluated the impact of photoperiod on circulatory hormonal parameters (triiodothyronine [T3], thyroxin [T4], estradiol [E2], progesterone [P4], melatonin, and insulin), their receptor expressions and key markers associated with redox (SIRT-1/FOXO-1), inflammatory (NFĸB/COX-2) and metabolic (IR/GLUT4) status in uterus. Adult female golden hamsters were exposed to different photoperiodic regimes, that is, short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. SP drastically decreased peripheral hormone profiles (T3, T4, E2, and P4) and compromised uterine histoarchitecture when compared with LP-exposed hamsters. Further, SP markedly decreased thyroid hormone receptor-α (TRα), insulin receptor, and glucose uptake transporter-4 (GLUT-4) expressions in uterus. We noted enhanced uterine oxidative (increased MDA and decreased SOD/CAT levels), SIRT-1/FOXO-1 expression and inflammatory (NFĸB/COX-2) load in SP condition. Further, elevated levels of circulatory insulin, melatonin, and its receptor (MT-1) expression in uterus was noted under SP condition. Thus, we may suggest that photoperiod might regulate uterine seasonality through modulation of local hormonal and redox/metabolic homeostasis thereby may restrict offspring bearing capacity under short days.

Investigation of the Histopathological Effects of Hyperthyroidism on Endometrial Tissue in an Experimental Hyperthyroidism Rat Model

Objective: It was aimed to investigate histopathological changes of rat uterus in experimental hyperthyroidism. Methods: 16 new adult Wistar albino female rats weighing 200-220 g were used. Group 1 (Control group) were given 3 ml distilled water for 25 days, Group 2 was given 100 µg/day of L-thyroxine dissolved in 3 mL distilled water by oral gavage for 25 days. In the uterine tissue sections, incubation was performed with the Caspase 3 primary antibody to detect apoptotic cell death and LC3B primary antibody to detect autophagic cell death. Immunositivities were evaluated and histological examination was performed. Results: In terms of apoptotic cell death, no immunopositivity was observed in both group. Differences were found between the groups in terms of autophagic cell death. It was observed that there is hyperplasia in some places in epithelial cells and the cells undergo degenerative changes. In the endometrium, edematous areas and mononuclear inflammatory cell infiltrations were noted. Conclusion: We have observed that hyperthyroidism causes edematous and inflammatory changes in the endometrium of adult rats, increases autophagy. We believe that the increase in autophagy is due to the effect of increased inflammation and impaired homeostasis. Detailed molecular studies are needed to investigate the effects of hyperthyroidism at the tissue level.

TSH receptor antibodies (TRAb) - A potential new biomarker for endometriosis

OBJECTIVES

The prevalence of several autoimmune diseases, including thyroid dysfunction, has been reported to be increased in patients with endometriosis. Upregulated thyroid stimulation hormone (TSH) receptors in ectopic endometrium and elevated serum titers of TSH receptor antibodies (TRAb) IgG in endometriosis patients indicates an overlap in pathophysiology. However, cross-reactivity with other antibodies must be excluded. The objective of this study was to compare the expression of autoantibodies in women with endometriosis and two control groups to evaluate the potential of TRAb IgG as a diagnostic marker for endometriosis.

STUDY DESIGN

This cross-sectional study was carried out in 172 women with surgically confirmed endometriosis and two control groups consisting of 50 healthy blood donors and 114 women from Malmö Offspring Study consisting of people from the general population. Serum levels of thyroid hormones, TSH and TRAb autoantibodies, AXIN1, and autoantibodies against follicle stimulating hormone (FSH), human chorionic gonadotropin (hCG), luteinizing hormone (LH), and their receptors, were analyzed. The patients answered a questionnaire and estimated their gastrointestinal symptoms using the Visual Analogue Scale for Irritable Bowel Syndrome.

RESULTS

Of the endometriosis patients, 29.1 % had TRAb IgG above the present detection limit of ≥ 1.0 IE/L compared to 2.6 % of the controls from MOS (p < 0.001) and 94.5 % had levels of TRAb over the previous detection limit ≥ 0.3 IE/L compared to 7.9 % of the controls (p < 0.001). Titers of both TRAb IgG and IgM were increased in patients compared to controls from MOS and blood donors, respectively (p < 0.001). There was no increase of autoantibodies against FSH, FSH receptor (FSHR), hCG, LH, LH receptor (LHR) or TSH compared to the blood donor controls. TRAb titers did not correlate with age, disease duration, AXIN1, TSH, thyroid hormones or gastrointestinal symptoms.

CONCLUSION

TRAb IgG and IgM are slightly elevated in patients with endometriosis with no cross-reactivity with other autoantibodies. The results indicate that TRAb is truly elevated and thereby has the potential to be used to support the diagnosing of endometriosis.

Unrevealing functional candidate genes for bovine fertility through RNA sequencing meta-analysis and regulatory elements networks of co-expressed genes and lncRNAs

The high genetic heterogeneity and environmental effects of subfertility in livestock species make the elucidation of the genetic mechanisms associated with reproductive efficiency a difficult task. Network and co-expression network meta-analyses were applied alongside genetic variant calling and long non-coding RNA (lncRNA) characterization to identify functionally relevant target genes and regulatory subnetworks associated with fertility in dairy cattle. In total, 505 lncRNAs (441 previously annotated in the bovine reference genome ARS-UCD 1.2 and 64 novel lncRNAs) were identified. Seven differentially expressed genes between high-fertile (HF) and sub-fertile (SF) Holstein cows were identified in the network meta-analysis (CA5A, ENSBTAG00000051149, ENSBTAG00000003272, DEFB7, DIO2, TRPV3, and COL4A4). Additionally, seven functional candidate differentially co-expressed (DcoExp) modules with a differential regulatory pattern (|z-score|>2) were identified between HF and SF cows. The functional candidate genes and DcoExp modules identified were associated with fertility relevant processes such as the regulation of embryonic implantation and proliferation, interaction and molecule transfer between the fetus and the cow, and the immune system. These results help to better understand the genetic mechanisms associated with reproductive efficiency in dairy cattle through the identification of potential biomarkers and genetic variants associated with differentially expressed regulatory gene and lncRNAs regulatory element networks.

Evaluation of the relationship between serum TSH levels and pregnancy outcomes of IVF/ICSI patients in follicular phase long-acting long protocol

ObjectiveTo investigate whether TSH levels are associated with the pregnancy outcomes of patients in the follicular phase long-acting long protocol of IVF/ICSI.MethodsThis was a single-central, retrospective study which was conducted in the Reproductive Medicine Center, Renmin Hospital of Wuhan University from February 2019 to April 2021. A total number of 773 patients underwent the follicular phase long-acting long protocol during in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment were divided into Group A (0.5 mIU/L ≤ TSH ≤2.5 mIU/L, n = 463) and Group B (2.5 mIU/L < TSH≤ 4.5 mIU/L, n = 310) according to their serum TSH levels. The clinical data and pregnancy outcomes were compared between the two groups. The possible relationship between TSH levels and pregnancy outcomes in people who performed follicular phase long-acting long protocol was investigated.ResultsThe proportion of patients with infertility due to ovulation disorders was significantly greater in Group B than in Group A (p = 0.036). The duration of Gn of Group B was significantly longer than that of Group A (p = 0.001). The Gn dose of Group B was significantly larger than that of Group A (p = 0.002). Besides, the implantation rate and miscarriage rate of embryos transferred on D3 were significantly higher in Group B than that of Group A (p = 0.033, p = 0.026 respectively).ConclusionsThe higher implantation and miscarriage rates of D3 of IVF/ICSI in the follicular phase long-acting long protocol may be related to higher serum TSH levels.

Chemerin Effect on the Endometrial Proteome of the Domestic Pig during Implantation Obtained by LC-MS/MS Analysis

Chemerin (CHEM) is a hormone mainly expressed in adipocytes involved in the regulation of energy homeostasis and inflammatory response. CHEM expression has been demonstrated in the structures of the porcine hypothalamic-pituitary-gonadal axis, as well as in the uterus, trophoblasts and conceptuses of pigs. In this study, we performed high-throughput proteomic analyses (liquid chromatography with tandem mass spectrometry, LC-MS/MS) to examine the influence of CHEM (400 ng/mL) on differentially regulated proteins (DRPs) in the porcine endometrial tissue explants during implantation (15 to 16 days of gestation). Among all 352 DRPs, 164 were up-regulated and 188 were down-regulated in CHEM-treated group. DRPs were assigned to 47 gene ontology (GO) terms (p-adjusted < 0.05). Validation of four DRPs (IFIT5, TGFβ1, ACO1 and PGRMC1) by Western blot analysis confirmed the veracity and accuracy of the LC-MS/MS method used in the present study. We suggest that CHEM, by modulating various protein expressions, takes part in the endometrial cell proliferation, migration and invasion at the time of implantation. It also regulates the endometrial immune response, sensitivity to P4 and the formation of new blood vessels. Additionally, CHEM appears to be an important factor involved in endothelial cell dysfunction during the pathogenesis of preeclampsia. The identification of a large number of DRPs under the influence of CHEM provides a valuable resource for understanding the molecular mechanisms of this hormone action during implantation, which is a prerequisite for better control of pig reproduction.

IVF/ICSI outcomes of euthyroid infertile women with thyroid autoimmunity: does treatment with aspirin plus prednisone matter?

Background

Thyroid autoimmunity (TAI) has been demonstrated to be associated with adverse pregnancy including recurrent miscarriage, unexplained infertility, and implantation failure. To settle with the fertility problem, prescribing aspirin combined with prednisone (P + A) to women positive for anti-thyroid antibodies is frequent in clinical practice, but the underlying effect remains controversial.

Methods

A multicenter, retrospective study was conducted in three reproductive centers from 2017 to 2020. A total of 494 euthyroid infertile women were recruited who were positive for anti-thyroperoxidase and/or thyroglobulin antibodies (TPOAb and TgAb, respectively) with thyroid-stimulating hormone (TSH) levels ranging 0.35-4.0mIU/L and underwent their first in vitro fertilization and embryo transfer (IVF-ET) cycle. Ultimately, 346 women were included of which 150 women were treated with prednisone (10 mg/d) and aspirin (100 mg/d). The remaining 196 women were untreated (control group). Treatment started on the day of embryo transfer and continued until clinical pregnancy was determined.

Results

The clinical pregnancy rate was 57.5% vs. 63.5% in the control and treated groups (P = 0.414) for first fresh embryo transfer cycles and 57.8% vs. 61.8% for frozen-thawed embryo transfer cycles (P = 0.606). In addition, the live birth rate for the fresh embryo transfer was 49.6% vs. 47.3% in the control and treated groups (P = 0.762). Logistic regression revealed that aspirin plus prednisone did not improve the clinical pregnancy rate or miscarriage rate. Furthermore, it was observed that low free triiodothyronine (FT3) was associated with high miscarriage rates.

Conclusions

Utilizing an adjuvant treatment of P + A after the embryo transfer may not be necessary in euthyroid women with thyroid autoimmunity undergoing their first IVF-ET, regardless of the embryo type (fresh or frozen).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04532-2.

Thyroid Dysfunction after Gonadotropin-Releasing Hormone Agonist Administration in Women with Thyroid Autoimmunity

GnRH agonists (GnRHa) are a useful tool for pretreatment before artificial endometrial preparation for frozen-thawed embryo-transfer (FET). Their prolonged administration has been associated with thyroid dysfunction, both hyper and hypothyroidism. The aim of this study is to investigate the impact of GnRHa administration on thyroid function in women undergoing artificial endometrial preparation. Seventy-eight euthyroid women undergoing endometrial preparation with hormone replacement for FET were retrospectively reviewed. They were divided into two groups according to pretreatment with GnRHa (group A, 42 women) or with an oral contraceptive (group B, 36 women). Group A was subsequently divided into two subgroups according to thyroid autoimmunity presence. Thyroid function has been evaluated and compared among groups and subgroups. Our results did not show any statistically significant differences in age, body mass index, and basal thyroid stimulating hormone (TSH). Total estradiol dosage, duration of treatment, and endometrial thickness were comparable among groups. When TSH was measured 14 days after embryo transfer, no significant differences between the two groups were reported. Among women of group A, TSH was significantly higher only in women with thyroid autoimmunity. GnRHa seems to be associated with thyroid dysfunction in women with thyroid autoimmunity undergoing hormone replacement therapy for FET.

Thyroid cancer in women of reproductive age: Key issues for the clinical team

Women who are fertile experience a significant burden from thyroid cancer. In reality, delaying childbirth is the current trend in maternity. Women who have thyroid cancer may later want to get pregnant after it has been treated, which presents a multidisciplinary issue for their doctors. A variety of specialists are frequently involved in the treatment of thyroid cancer. This review aims to address the key elements of the strategy and places special emphasis on the significance of fertility in women with thyroid cancer diagnosis and remission. We will cover topics including the role of thyroid hormones in pregnancy and fertility.

Expression of Cytokines and Cytokine Receptors-Genes in Patients with Different Forms of Thyroid Pathology in Ukrainian Population

Multiple susceptibility genes can be involved in the development of Hashimoto’s thyroiditis. Some of these genes are implicated in other autoimmune diseases, while others are specific to thyroid autoimmune response. 153 patients with thyroid pathology were enrolled in the study (152 women and 1 man, the average age was 46,02±14,3). They were divided into 3 groups: 16 patients with postoperative hypothyroidism; 65 patients with hypothyroidism resulting from autoimmune thyroiditis, and 72 patients with both AIT and elevated serum an anti-thyroglobulin and anti-thyroid peroxidase antibodies. We used a pathway-specific real-time Polymerase chain reaction array to identify and verify cytokines and receptor pathway-associated gene expression in peripheral white blood cells in randomly selected 12 individuals from each group. In the patients with postoperative hypothyroidism and those with hypothyroidism resulting from autoimmune thyroiditis, the expression of Chemokine (C-X3-C motif) receptor 1, Chemokine (C-X-C motif) receptor 4, Interleukin 6, and Interleukin 6 receptor significantly decreased, while the expression of IL6ST and IL10RA increased. In contrast, mRNA levels of Chemokine (C-X3-C motif) receptor 1, Chemokine (C-X-C motif) receptor 4, Interleukin 6, and Interleukin 6 receptor increased in the autoimmune thyroiditis patients with elevated serum anti-thyroglobulin and anti-thyroid peroxidase antibodies, while the expression of Interleukin 6 signal transducer and Interleukin 10 receptor, alpha decreased in this group of patients. The patients with hypothyroidism resulting from autoimmune thyroiditis and patients with elevated serum anti-thyroglobulin and anti-thyroid peroxidase antibodies had significantly lowered expression of Interleukin 10, while the expression of Interleukin 1, beta and Interleukin 1 receptor, type I was elevated. autoimmune thyroiditis and hypothyroidism affect the mRNA-level expression of cytokines and cytokine receptor genes in a gene-specific manner, and these changes to gene expression can be among the triggers of autoimmune inflammation progression in the thyroid gland. Transcriptional activity of cytokines, inducer, and receptor genes in the peripheral white blood cells can be used as an important minimally invasive prognostic marker of the autoimmune thyroid disease severity.

Is the link between elevated TSH and gestational diabetes mellitus dependant on diagnostic criteria and thyroid antibody status: a systematic review and meta-analysis

PURPOSE

Clinical studies have investigated the prevalence of gestational diabetes mellitus (GDM) in women with subclinical hypothyroidism (SCH). While some studies demonstrate a clear association, others do not. It is possible this may be due to varied diagnostic criteria for SCH and the presence of thyroid antibodies (TA). We conducted a meta-analysis, separating patients diagnosed with SCH using a diagnostic cut-off <4.0 mIU/L from those diagnosed using a cut-off >4.0 mIU/L and determined the association with GDM and factored TA status into our analysis.

METHODS

A computerised search of five databases including PubMed, Embase, Cochrane Library, Web of Science and CINAHL returned 787 records. Two independent reviewers assessed abstracts and full texts against pre-specified inclusion and exclusion criteria. Ten cohort studies were included in the final analysis. The diagnostic criteria for SCH and incidence of GDM were extracted from each study. Study quality and risk of bias was assessed by two reviewers.

RESULTS

TSH levels <4.0 mIU/L for SCH diagnosis was not associated with GDM unless patients were TA positive. Studies that used a diagnostic cut-off >4.0 mIU/L saw a significant increase in the odds of GDM, regardless of TA status (OR = 1.60, 95% CI 1.33-1.93).

CONCLUSIONS

Women with TSH levels >4.0 mIU/L have an increased odds of GDM regardless of TA status but at TSH levels <4.0 mIU/L, GDM is dependent on TA status. The use of TSH levels to identify pregnancies at risk of GDM is a novel concept that warrants exploration.

Analysis of in vitro fertilization/intracytoplasmic sperm injection outcomes in infertile women with a history of thyroid cancer: a retrospective study

BACKGROUND

Recent studies have revealed that women with infertility have a higher risk of thyroid cancer (TC) than fertile women. However, studies on whether a history of thyroid cancer affects clinical outcomes in women who conceive using in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) are scarce. We investigate whether a history of thyroid cancer (TC) affects the in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcomes and increases the risk of adverse obstetric outcomes in women with infertility.

METHODS

This retrospective study enrolled 384 women with infertility who underwent their first IVF/ICSI treatment at the Peking University Third Hospital between 2010 and 2019. Participants were divided into the TC (64 women with TC history) and control (320 women matched from 85,272 women without thyroid diseases) groups. Controls were individually matched to the TC group according to age, body mass index, concomitant infertility factors, first IVF/ICSI dates, and controlled ovarian stimulation and embryo transfer procedure protocols. IVF/ICSI outcomes, including the numbers of retrieved oocytes and high-grade embryos, clinical pregnancy, miscarriage, preterm delivery, and live birth rates, and adverse obstetric outcome risk were assessed.

RESULTS

The TC group had significantly higher thyroid hormone and lower thyroid-stimulating hormone (TSH) levels than the control group. Despite similar gonadotropin treatment dosage, the TC group had a significantly lower numbers of retrieved oocytes and high-grade embryos than the control group. The occurrence rates of clinical pregnancy, miscarriage, preterm delivery, live births, and adverse obstetric outcomes, including multiple gestation, preterm delivery, gestational diabetes mellitus, gestational hypertension, low birth weight, and large-for-gestational-age infants, were not significantly different between the two groups.

CONCLUSIONS

TC history did not affect the pregnancy outcomes or increase the risk of adverse obstetric outcomes after the first IVF/ICSI, but it may decrease the number of retrieved oocytes and high-grade embryos.

Changes in thyroid function during controlled ovarian hyperstimulation (COH) and its impact on assisted reproduction technology (ART) outcomes: a systematic review and meta-analysis

BACKGROUND

To investigate the thyroid function changes during controlled ovarian hyperstimulation (COH) and ascertain its impact on reproductive outcomes.

METHODS

We conducted meta-analysis in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive literature search was performed to identify studies reported changes in thyroid parameters during COH. We analyzed thyroid-stimulating hormone (TSH) levels, free thyroxin (fT4) levels, changes in estrogens (E2), thyroxine-binding globulin (TBG), relative risks (RRs) of clinical pregnancy rate (CPR), live birth rate (LBR), and mean difference (MD) of TSH increment between the miscarriage group and ongoing pregnancy group.

RESULTS

This meta-analysis included fifteen individual studies (n = 1665 subjects). At the end of COH, the mean TSH (2.53 mIU/L; 95% CI, 2.19 to 2.88; I² = 92.9%) exceeded the upper limit (2.5 mIU/L) and remained above the threshold until one month following embryo transfer (ET). Thyroxin decreased from baseline to the end of COH (-0.18 ng/l; 95% CI, -0.35 to 0.00; I² = 92.2%). The CPR and LBR of patients with TSH exceeding the cutoff after COH were significantly lower than those of patients with TSH below the threshold (CPR: RR, 0.62; 95% CI, 0.47 to 0.82; I² = 0.0% and LBR: RR, 0.64; 95% CI, 0.44 to 0.92; I² = 0.0%). The MD of the increment in TSH levels between the miscarriage and ongoing pregnancy groups was 0.40 mIU/L (95% CI, 0.15 to 0.65; I² = 0.0%).

CONCLUSIONS

This meta-analysis shows that TSH increases and fT4 decreases during COH. COH-induced thyroid disorder impairs reproductive outcomes.

Primary juvenile hypothyroidism concurrent with huge bilateral cystic ovaries: Case report and literature review

Primary hypothyroidism can lead to delayed growth and pseudoprecocious puberty in juvenile patients, which was known as Van Wyk-Grumbach's syndrome (VWGS). There have been very few clinical case reports of primary juvenile hypothyroidism presenting with concurrent huge bilateral cystic ovaries. Here, we report the case of a 14-year-old female patient suffering from primary hypothyroidism in combination with bilateral cystic ovaries. Remarkable improvement of symptoms was observed after one month of hormone replacement therapy and an unnecessary surgical treatment was avoided. A comprehensive literature review of VWGS is summarised here to illustrate the presentation, diagnosis, and treatment of VWGS in pediatric patients. The present study aims to improve the current clinical knowledge of VWGS.

Elevated non-essential metals and the disordered metabolism of essential metals are associated to abnormal pregnancy with spontaneous abortion

Spontaneous abortion is a considerable threat to the physiology and mental health of the mother. The etiology of spontaneous abortion is multifactorial with complicated mechanisms, of which overexposure to non-essential metals (especially heavy metals) has been proposed to be associated with adverse birth outcomes. However, significant knowledge gaps remain to be filled in, such as the deleterious profile of non-essential metals and their interplay with essential metals in abnormal pregnancy. Under this setting, we aimed to address these challenges by conducting a cross-sectional study on 56 patients with spontaneous abortion in the 1^st trimester, by comparing to 55 healthy pregnant women in 1^st the trimester and 41 non-pregnant healthy women. Overexposure to a few non-essential metals, such as arsenic (As), antimony (Sb) and bismuth (Bi), was found in patients with spontaneous abortion, and likewise, some essential elements, such as magnesium (Mg), copper (Cu), vanadium (V), strontium (Sr) and tin (Sn), were also found to be elevated under spontaneous abortion. Further evidence of abnormal pregnancy was induced by a reduced level of internal hormones necessary for normal gestation, such as estradiol (E2) and progesterone (PRGE) in women with spontaneous abortion. Lactate dehydrogenase (LDH) and thyroid-stimulating hormone (TSH) levels were slightly increased in patients with spontaneous abortion. Comprehensive correlation analyses were carried out to identify the crucial factors that result in abortion. Our data stratified the important variables in decreasing order: PRGE, As, Mg, Sb, Sr, Sn, Bi and pregnant times in the progress of spontaneous abortion. Moreover, labyrinthine associations were uncovered between PRGE, non-essential metals and essential elements in causing spontaneous abortion. Therefore, our combined data unveiled the likely synergistic implications of elevated non-essential metals and the disordered metabolism of essential metals in abnormal pregnancy.

Thyroid peroxidase in human endometrium and placenta: a potential target for anti-TPO antibodies

Autoimmune thyroid disease is the most common endocrine disorder during pregnancy. Thyroid autoantibodies (TAs) have been suggested to serve a role in implantation failure and spontaneous abortion. Until now, there are no data on the potential interaction of TAs with human reproductive organs. Here, we set out for the first time to test this hypothesis by studying the expression of thyroid peroxidase (TPO) at gene and protein level in human reproductive organs. Endometrial samples were taken from normal women, and placenta tissues were collected after full-term caesarian section. Expression of TPO messenger RNA (mRNA) was investigated by qRT-PCR. In addition, polyclonal anti-TPO antibodies were produced and the expression of TPO protein in mentioned tissues was evaluated by immunohistochemistry and Western blot analysis. The reactivity of anti-TPO antibody in human embryos was evaluated by immunofluorescent staining. For the first time, our study showed that TPO is expressed at gene and protein levels in endometrium and placenta. TPO expression was mainly localized to glandular and luminal epithelial cells in the endometrium. In placenta, the syncytiotrophoblasts and invasive trophoblast cells were the main cell types that expressed TPO protein. Specific band of approximately 110 kDa was observed in all endometrial and placental tissues by Western blot analysis. However, no expression of TPO protein was observed in human embryo. TPO expression in endometrium and placenta may explain higher frequency of abortion and infertility in patients with thyroid autoimmunity.

The Molecular Function and Clinical Role of Thyroid Stimulating Hormone Receptor in Cancer Cells

The thyroid stimulating hormone (TSH) and its cognate receptor (TSHR) are of crucial importance for thyrocytes to proliferate and exert their functions. Although TSHR is predominantly expressed in thyrocytes, several studies have revealed that functional TSHR can also be detected in many extra-thyroid tissues, such as primary ovarian and hepatic tissues as well as their corresponding malignancies. Recent advances in cancer biology further raise the possibility of utilizing TSH and/or TSHR as a therapeutic target or as an informative index to predict treatment responses in cancer patients. The TSH/TSHR cascade has been considered a pivotal modulator for carcinogenesis and/or tumor progression in these cancers. TSHR belongs to a sub-group of family A G-protein-coupled receptors (GPCRs), which activate a bundle of well-defined signaling transduction pathways to enhance cell renewal in response to external stimuli. In this review, recent findings regarding the molecular basis of TSH/TSHR functions in either thyroid or extra-thyroid tissues and the potential of directly targeting TSHR as an anticancer strategy are summarized and discussed.

Morphological spectrum of endometrium with thyroid hormone profile in infertile female population of Khyber Pakhtunkhwa province of Pakistan

Objectives:

To study the morphological spectrum of endometrial changes with the thyroid hormone levels in infertile women.

Methods:

This cross sectional study was conducted at Department of Pathology, Peshawar Medical College, Health Care Centre and Madina Medical Laboratory, Peshawar from April 2013 to August 2013. Total 160 cases of infertile women were included in the study. Biopsies were taken on 22-23rd day of menstrual cycle. Statistical Analysis was performed using SPSS version 19 statistical program. Difference between endometrial findings of patients with normal thyroid profile and abnormal one were analyzed for statistical significance using Chi square test. Probability values p ≤ 0.05 were considered statistically significant.

Results:

In our study, majority infertile women were euthyroid (80%), followed by hyperthyroid (18%) and only two% to be hypothyroid. The correlation of endometrial morphology with thyroid hormones levels turned out to be insignificant. While correlating histological details of endometrial biopsy with thyroid hormone status, we found significant association of leukocytic infiltrate with thyroid hormone levels.

Conclusion:

This study shows that thyroid hormones may have role in early leukocytic infiltration into stroma, and a possibility of immune modulation by altered thyroid hormones in causing infertility.

Thyroid Hormone Facilitates in vitro Decidualization of Human Endometrial Stromal Cells via Thyroid Hormone Receptors

Endometrial stromal cells differentiate into decidual cells through the process of decidualization. This differentiation is critical for embryo implantation and the successful establishment of pregnancy. Recent epidemiological studies have suggested that thyroid hormone is important in the endometrium during implantation, and it is commonly believed that thyroid hormone is essential for proper development, differentiation, growth, and metabolism. This study aimed to investigate the impact of thyroid hormone on decidualization in human endometrial stromal cells (hESCs) and define its physiological roles in vitro by gene targeting. To identify the expression patterns of thyroid hormone, we performed gene expression profiling of hESCs during decidualization after treating them with the thyroid hormone levothyroxine (LT4). A major increase in decidual response was observed after combined treatment with ovarian steroid hormones and thyroid hormone. Moreover, LT4 treatment also affected the regulation of many transcription factors important for decidualization. We found that type 3 deiodinase, which is particularly important in fetal and placental tissues, was upregulated during decidualization in the presence of thyroid hormone. Further, it was observed that progesterone receptor, an ovarian steroid hormone receptor, was involved in thyroid hormone-induced decidualization. In the absence of thyroid hormone receptor (TR), due to the simultaneous silencing of TRα and TRβ, thyroid hormone expression was unchanged during decidualization. In summary, we demonstrated that thyroid hormone is essential for decidualization in the endometrium. This is the first in vitro study to find impaired decidualization as a possible cause of infertility in subclinical hypothyroidism (SCH) patients.

Effect of levothyroxine supplementation on pregnancy loss and preterm birth in women with subclinical hypothyroidism and thyroid autoimmunity: a systematic review and meta-analysis

BACKGROUND

Subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI) are associated with adverse pregnancy outcomes such as pregnancy loss and preterm birth. However, the ability of levothyroxine (LT4) supplementation to attenuate the risks of these outcomes remains controversial.

OBJECTIVE AND RATIONALE

This systematic review and meta-analysis was conducted to determine the effect of LT4 supplementation on pregnancy loss rate (PLR) and preterm birth rate (PBR) among pregnant women with SCH and TAI.

SEARCH METHODS

A systematic literature search of the PubMed, EMBASE, Web of Science and Cochrane Controlled Trials Register databases and Clinicaltrials.gov was performed to identify all relevant English studies published up to April 2018. The following terms were used for the search: [subclinical hypothyroidism OR thyroid autoimmunity OR thyroperoxidase antibody (TPO-Ab) OR thyroglobulin antibodies (Tg-Ab)] AND (levothyroxine OR euthyrox) AND [pregnancy outcome OR miscarriage OR abortion OR pregnancy loss OR preterm birth OR premature delivery OR early labo(u)r]. The reference lists of the relevant publications were also manually searched for related studies. Published manuscripts were included if they reported data on pregnancy loss, preterm birth or both. We separately analysed the pooled effects of LT4 supplementation on PLR and PBR in women with SCH and TAI.

OUTCOMES

Overall, 13 eligible studies including 7970 women were included in the meta-analysis. Eight and five of these studies were randomized controlled trials (RCTs) and retrospective studies, respectively. The pooled results indicated that LT4 supplementation significantly decreased the PLR [relative risk (RR) = 0.56, 95% confidence interval (CI): 0.42-0.75, I2 = 1%, 12 studies] and PBR (RR = 0.68, 95% CI: 0.51-0.91, I2 = 21%, eight studies) in women with SCH and/or TAI. We further found that LT4 supplementation significantly decreased the risk of pregnancy loss (RR = 0.43, 95% CI: 0.26-0.72, P = 0.001, I2 = 0%) but not of preterm birth (RR = 0.67, 95% CI: 0.41-1.12, P = 0.13, I2 = 0%) in women with SCH. Furthermore, LT4 supplementation significantly decreased the risks of both pregnancy loss (RR = 0.63, 95% CI: 0.45-0.89, P = 0.009, I2 = 0%) and preterm birth (RR = 0.68 95% CI: 0.48-0.98, P = 0.04, I2 = 46%) in women with TAI. These results were consistent when only RCTs were included in the analysis. Further, in women with SCH, LT4 supplementation reduced the risk of pregnancy loss in pregnancies achieved by assisted reproduction (RR = 0.27, 95% CI: 0.14-0.52, P < 0.001, I2 = 14%) but not in naturally conceived pregnancies (RR = 0.60, 95% CI: 0.28-1.30, P = 0.13, I2 = 0%). By contrast, in women with TAI, LT4 supplementation reduced the risks of both pregnancy loss (RR = 0.61, 95% CI: 0.39-0.96, P = 0.03, I2 = 0%) and preterm birth (RR = 0.49, 95% CI: 0.30-0.79, P = 0.003, I2 = 0%) in naturally conceived pregnancies but not in pregnancies achieved by assisted reproduction (RR = 0.68, 95% CI: 0.40-1.15, P = 0.15, I2 = 0% for pregnancy loss and RR = 1.20, 95% CI: 0.68-2.13, P = 0.53, I2 not applicable for preterm birth).

WIDER IMPLICATIONS

This meta-analysis confirmed the beneficial effects of LT4 supplementation, namely the reduced risks of pregnancy loss and preterm birth, among pregnant women with SCH and/or TAI. The different effects of LT4 supplementation on naturally conceived pregnancies and pregnancies achieved by assisted reproduction in women with SCH and/or TAI suggest that these women should be managed separately. Due to the limited number of studies included in this meta-analysis, especially in the subgroup analysis, further large RCTs and fundamental studies are warranted to confirm the conclusions and better clarify the molecular mechanism underlying these associations.

Thyroid and Fertility: Recent Advances

Background: Thyroid disease is prevalent in women of reproductive age, while infertility is common in women with thyroid dysfunction. In this study, we review the recent advances in the field of thyroid and fertility since the publication of the 2017 American Thyroid Association pregnancy guidelines. Summary: Recent studies have confirmed associations of thyrotropin (TSH) elevation and/or thyroid autoimmunity with infertility and low ovarian reserve in subsets of women, and have led to a better understanding of the pathogenesis linking thyroid autoimmunity with infertility. Even though the benefit of treating patients with TSH >4 mIU/L has been confirmed in a large retrospective cohort study, two large randomized controlled trials have failed to show benefit of thyroid hormone on obstetrical outcomes in euthyroid women with thyroid autoimmunity. New data have emerged regarding the potential gonadal toxicity of radioactive iodine (RAI), based on its impact on ovarian reserve and sperm chromosomal abnormalities. Conclusions: There is continued evidence supporting an important role of thyroid hormone in regulation of reproductive tissues at many levels. Recent randomized trials have failed to identify a benefit of thyroid hormone in euthyroid women with thyroid autoimmunity. Further research in the field is needed to more completely delineate the relevant pathways and identify women who may benefit from levothyroxine treatment. The impact of RAI on fertility also merits further investigation.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

Serum and follicular fluid thyroid hormone levels and assisted reproductive technology outcomes

OBJECTIVE

The objective ofthis study was to assess the association between thyroid hormone (TH) levels in follicular fluid (FF) and serum and to determine whether THs impact assisted reproductive technology (ART) outcomes.

METHODS

This study enrolled 299 women undergoing ART. Blood samples were drawn on the day of human chorionic gonadotrophin (HCG) administrationand analysed for thyroid-stimulating hormone (TSH), thyroxine(T4), triiodothyronine(T3),free T4 (fT4),free T3(fT3), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) levels. FF was obtained on the oocyte pick up (OPU) day and analysed forTSH, T4, T3, fT4, fT3, TPOAb, TgAb and estradiol levels.

RESULTS

(1) There were significant positive correlations between serum and FF TH and thyroid autoantibody levels. Statistically significant differences were discovered in serum and FF levels of TSH (p ≤ 0.001), T4 (p ≤ 0.001), T3 (p ≤ 0.001), TPOAbs (p ≤ 0.001) and TGAbs (p = 0.021). (2) Serum T4 levels [121.9(104.8,140.8) vs 114.1(98.6,130.6) nmol/l, p = 0.026], serum fT4 levels[(19.0(17.7,21.8) vs 18.6(17.0,20.1) pmol/l, p = 0.026], serum T4/T3 ratios [62.5 (55.7, 66.2) vs 59.4 (53.4, 64.9), p = 0.029], FF fT4 levels [19.0(17.5,21.3) vs 18.1(16.8,19.9) pmol/l, p = 0.009] and FF T4/T3 ratios [52.6 (46.4, 57.3) vs 50.0 (43.7, 53.1), p = 0.004] were significantly higher in the successful pregnancy group than the implantation failure group. (3) Spearman's rank correlation analysis revealed positive associations of both the FF T4/T3 ratio and serum TSH levels with the numbers of retrieved oocytes (total or MII) and embryos (fertilized, cleavage, and good quality).

CONCLUSIONS

TH levels in FF are strongly correlated with those in serum on the HCG day, and THs on the HCG day may affect ART outcomes.

Thyroid hormones and female reproduction

Thyroid hormones are vital for the proper functioning of the female reproductive system, since they modulate the metabolism and development of ovarian, uterine, and placental tissues. Therefore, hypo- and hyperthyroidism may result in subfertility or infertility in both women and animals. Other well-documented sequelae of maternal thyroid dysfunctions include menstrual/estral irregularity, anovulation, abortion, preterm delivery, preeclampsia, intrauterine growth restriction, postpartum thyroiditis, and mental retardation in children. Several studies have been carried out involving prospective and retrospective studies of women with thyroid dysfunction, as well as in vivo and in vitro assays of hypo- and hyperthyroidism using experimental animal models and/or ovarian, uterine, and placental cell culture. These studies have sought to elucidate the mechanisms by which thyroid hormones influence reproduction to better understand the physiology of the reproductive system and to provide better therapeutic tools for reproductive dysfunctions that originate from thyroid dysfunctions. Therefore, this review aims to summarize and update the available information related to the role of thyroid hormones in the morphophysiology of the ovary, uterus, and placenta in women and animals and the effects of hypo- and hyperthyroidism on the female reproductive system.

Maternal TSH levels at first trimester and subsequent spontaneous miscarriage: a nested case-control study

Thyroid dysfunction is a frequently found endocrine disorder among reproductively aged women. Subclinical hypothyroidism is the most common condition of thyroid disorders during pregnancy and is defined as manifesting a thyroid-stimulating hormone concentration exceeding the trimester-specific reference value, with a normal free thyroxine concentration. Here, we evaluated the prospective association between spontaneous miscarriage and first-trimester thyroid function. We conducted a case-control study (421 cases and 1684 controls) that was nested. Thyroid-stimulating hormone (TSH), free thyroxine (FT4), thyroid-peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) status were measured. We found that higher TSH was related to spontaneous miscarriage (OR 1.21; 95% CI, 1.13-1.30, P < 0.001). Compared with women with TSH levels of 0.4-<2.5 mIU/L, the risk of miscarriage was increased in women with TSH levels of 2.5-<4.87 mIU/L (OR 1.47; 95% CI, 1.16-1.87) and TSH greater than 4.87 mIU/L (OR 1.97; 95% CI, 1.22-3.18). After controlling for the confounding factor, TPOAb positivity status and FT4, the results were similar. The present study showed that higher TSH was associated with miscarriage in early pregnancy. In fact, TSH levels between 2.5 and 4.87 mIU/L increased the risk for miscarriage, with TSH greater than 4.87 mIU/L increasing the risk even further.

Role of thyroid dysimmunity and thyroid hormones in endometriosis

Endometriosis is characterized by the presence of ectopic endometrial cells outside the uterine cavity. Thyroid autoimmunity has been associated with endometriosis. This work investigated the potential pathophysiological link between endometriosis and thyroid disorders. Transcripts and proteins involved in thyroid metabolism are dysregulated in eutopic and ectopic endometrium of endometriotic patients, leading to resistance of ectopic endometrium to triiodothyronine (T3) action and local accumulation of thyroxine (T4). Thyroid-stimulating hormone (TSH) acts as a proliferative and prooxidative hormone on all endometria of endometriosis patients and controls, whereas T3 and T4 act to specifically increase ectopic endometrial cell proliferation and reactive oxygen species (ROS) production. Mouse studies confirmed the data gained in vitro since endometriotic implants were found to be bigger when thyroid hormones increased. A retrospective analysis of endometriosis patients with or without a thyroid disorder revealed an increased chronic pelvic pain and disease score in endometriotic patients with a thyroid disorder.

Implantation failure in rats with subclinical hypothyroidism is associated with LIF/STAT3 signaling

BACKGROUND

Pregnant women with subclinical hypothyroidism are associated with an increased risk of spontaneous abortion. This study aims to investigate the mechanisms underlying the effects of maternal subclinical hypothyroidism during early pregnancy on abortion in the uterus, focusing upon the LIF/STAT3 signaling pathway.

METHODS

One hundred five Wistar rats were randomly divided into three groups (35 rats in each group): control (CON) group, subclinical hypothyroidism (SCH) group and overt hypothyroidism (OH) group. We examined the weight of rat uteri, rat placenta and embryos. We also determined the number of implantation sites and the embryo absorption rates. The protein and mRNA expressions of TSHR, TR-α, TR-β, LIFR, gp130, JAK1, p-STAT3 and STAT3 were measured by immunohistochemical staining, real-time PCR and Western blotting.

RESULTS

The weights of rat uteri, rat placenta and embryos were significantly reduced in the SCH and OH groups. The number of implantation sites was significantly decreased in the SCH and OH groups, while embryo absorption rates were significantly increased. The mRNA and protein expressions of TSHR were upregulated in the SCH and OH groups, while TR-α and TR-β showed no difference when compared between the three groups. The expression levels of LIFR, gp130, JAK1 and p-STAT3 were significantly higher in the SCH and OH groups.

CONCLUSIONS

Clinical and subclinical hypothyroidism during early pregnancy might cause adverse pregnancy outcomes. Implantation failure in rats with subclinical hypothyroidism was associated with abnormal LIF/STAT3 signaling.

Expression of proteins related to thyroid hormone function in the uterus is down-regulated at the day of implantation in hypothyroid pregnant rats

Hypothyroidism has been linked to infertility, but the mechanisms underlying infertility-related hypothyroidism have yet to be fully elucidated. Therefore, in this study, effects of hypothyroidism on expression of the proteins related to thyroid hormone function in the uterus, which were thought to play a role implantation, including thyroid hormone receptor (TR), thyroid stimulating hormone receptor (TSHR), retinoic acid receptor (RAR) and extracellular kinase (ERK) were identified. Pregnant female rats were rendered hypothyroid by giving methimazole (MMI), orally. Following hypothyroid induction, rats were grouped into control (non-treated) and received subcutaneous thyroxine at 20, 40, and 80 μg/kg/day for five consecutive days. At Day 6, which is the day of implantation (GD 6), rats were sacrificed and the number of embryo implantation site in the uterus was calculated. Then, uterine horns were harvested and expression of the above proteins and their mRNAs were identified by Western blotting and real-time PCR, respectively. In non-treated hypothyroid pregnant rats, the number of embryo implantation sites decreased as compared to euthyroid and hypothyroid rats receiving thyroxine treatment. Similarly, expression of TRα-1, TRβ-1, TSHR, ERK1/2 and RAR proteins and mRNA in the uterus of non-treated hypothyroid rats also decreased (P < 0.05 when compared to euthyroid and thyroxine-treated hypothyroid rats). In conclusion, downregulated expression of the thyroid hormone related proteins in the uterus at the day of implantation might result in infertility as reported in hypothyroid condition.

Relationship between Hypothyroidism and Endometrial Cancer

Thyroid dysfunction is involved in several types of carcinoma. Hypothyroidism is one of the most common medical morbidities among patients with endometrial cancer; however, the related mechanism is unclear. Among the risk factors related to endometrial cancer, hypothyroidism interacts with metabolic syndrome, polycystic ovarian syndrome and infertility or directly acts on the endometrium itself, which may influence the development and progression of endometrial cancer. We summarize recent studies on the relationship between hypothyroidism and endometrial cancer and its risk factors to provide references for basic research as well as for clinical treatment and prognostic evaluation.

Does subclinical hypothyroidism and/or thyroid autoimmunity influence the IVF/ICSI outcome? Review of the literature

While overt hypothyroidism is a well-known risk factor for infertility, the association of subclinical hypothyroidism (SCH) or thyroid autoimmunity and reproductive failure has been still not elucidated. In this literature review, the current data on the effect of SCH and/or thyroid autoimmunity and human reproduction is presented. The main ART outcome measures are as follows: number of oocytes retrieved, fertilization rate, implantation rate, clinical pregnancy rate per embryo transfer, embryo quality, miscarriage rate, and live birth rate. Current guidelines on the management of women with SCH and/or thyroid autoimmunity undergoing ART cycles will be presented in this review.

Characteristics of endometriosis: A case-cohort study showing elevated IgG titers against the TSH receptor (TRAb) and mental comorbidity

OBJECTIVES

Endometriosis has been associated with a wide range of factors. The disease share immunological features with autoimmune diseases, and the prevalence of both hypo- and hyperthyroidism has been reported to be increased. However, the associations have to be confirmed and the mechanisms explored. The aim of this observational study was to investigate socioeconomic factors, lifestyle habits, and somatic and mental comorbidities in endometriosis compared to the general population.

STUDY DESIGN

In all, 172 women with endometriosis completed a study questionnaire and were interviewed regarding socioeconomic factors, lifestyle habits, psychological well-being, and medical history. Bowel symptoms were measured by the Visual Analogue Scale for Irritable Bowel Syndrome (VAS-IBS). Serum was analyzed for IgG levels of TSH receptor antibodies (TRAb) and anti-thyroid peroxidase (TPO) antibodies. Women from the general population served as controls. Differences were calculated by logistic regression, adjusted for confounders.

RESULTS

Alcohol intake, leisure time physical activity, body mass index and asthma were inversely, whereas IBS was positively associated with endometriosis. Hypothyroidism and anti-TPO antibodies did not associate, but elevated TRAb antibody titers were associated with endometriosis (odds ratio (OR): 539.26; 95% confidence interval (CI): 114.29-2544.32 for highest versus lowest tertile; p for trend < 0.001). Impaired psychological well-being (p for trend = 0.003) and current intake of antidepressant medication (OR: 3.54; 95% CI: 1.22-10.28; p = 0.020) associated with endometriosis, and impaired psychological well-being correlated with all gastrointestinal symptoms measured (all p < 0.001).

CONCLUSIONS

Lifestyle habits and asthma are inversely associated, and IBS and impaired psychological well-being are positively associated with endometriosis. TRAb titers are associated with endometriosis, supporting a link between endometriosis, autoimmunity and thyroid pathophysiology, although overt thyroid diseases do not associate.

Two Hormones for One Receptor: Evolution, Biochemistry, Actions, and Pathophysiology of LH and hCG

LH and chorionic gonadotropin (CG) are glycoproteins fundamental to sexual development and reproduction. Because they act on the same receptor (LHCGR), the general consensus has been that LH and human CG (hCG) are equivalent. However, separate evolution of LHβ and hCGβ subunits occurred in primates, resulting in two molecules sharing ~85% identity and regulating different physiological events. Pituitary, pulsatile LH production results in an ~90-minute half-life molecule targeting the gonads to regulate gametogenesis and androgen synthesis. Trophoblast hCG, the "pregnancy hormone," exists in several isoforms and glycosylation variants with long half-lives (hours) and angiogenic potential and acts on luteinized ovarian cells as progestational. The different molecular features of LH and hCG lead to hormone-specific LHCGR binding and intracellular signaling cascades. In ovarian cells, LH action is preferentially exerted through kinases, phosphorylated extracellular-regulated kinase 1/2 (pERK1/2) and phosphorylated AKT (also known as protein kinase B), resulting in irreplaceable proliferative/antiapoptotic signals and partial agonism on progesterone production in vitro. In contrast, hCG displays notable cAMP/protein kinase A (PKA)-mediated steroidogenic and proapoptotic potential, which is masked by estrogen action in vivo. In vitro data have been confirmed by a large data set from assisted reproduction, because the steroidogenic potential of hCG positively affects the number of retrieved oocytes, and LH affects the pregnancy rate (per oocyte number). Leydig cell in vitro exposure to hCG results in qualitatively similar cAMP/PKA and pERK1/2 activation compared with LH and testosterone. The supposed equivalence of LH and hCG has been disproved by such data, highlighting their sex-specific functions and thus deeming it an oversight caused by incomplete understanding of clinical data.

Association of Thyroid Function and Autoimmunity with Ovarian Reserve in Women Seeking Infertility Care

BACKGROUND

While overt thyroid disease is a well known risk factor for infertility, the potential consequences of mild thyroid dysfunction or thyroid autoimmunity remain unknown. Experimental studies suggest a considerable role for thyroid hormone in the physiological mechanisms of ovarian reserve, but translation of such findings to human studies remains rare. A potential role for thyroid function in female reproduction could be especially relevant when the cause of infertility remains unknown, such as in women with diminished ovarian reserve (DOR) or unexplained infertility. The aims of this study were to investigate the association of thyroid function and autoimmunity with markers of ovarian reserve day 3 follicle-stimulating hormone (FSH) concentrations and antral follicle count (AFC), and to investigate whether thyroid function or autoimmunity may have different effects in women with DOR or unexplained infertility.

METHODS

Thyrotropin, free thyroxine, thyroxine, free triiodothyronine (fT3), triiodothyronine, thyroid peroxidase antibodies (TPOAbs), and thyroglobulin antibodies (TgAbs), as well as AFC and the day 3 FSH concentration, were measured among women seeking fertility treatment at the Massachusetts General Hospital Fertility Center. Multiple linear or mixed regression models were used to study the association of thyroid function or autoimmunity with AFC or day 3 FSH.

RESULTS

In the total study population (436 women, 530 AFC measurements), there was no association of thyroid function or TPOAb positivity with AFC. However, TgAb positivity was associated with a higher AFC (mean difference = 3.4 [95% confidence interval (CI) 1.8-5.1], p < 0.001). In women with DOR or unexplained infertility, lower fT3 and TPOAb positivity were associated with a lower AFC (fT3: continuous nonlinear association, p = 0.009; TPOAb positivity: -2.3 follicles [confidence interval -3.8 to -0.5], p = 0.01), while TgAb positivity was not associated with AFC. Neither thyroid function nor thyroid antibody positivity was associated with the day 3 FSH concentration.

CONCLUSIONS

This study found that lower fT3 and TPOAb positivity are associated with a lower AFC in women with DOR or unexplained infertility. Future studies are required to replicate these findings and further elucidate the role of TgAbs and underlying mechanisms through which thyroid function and autoimmunity is associated with ovarian reserve.

Effect of levothyroxine supplementation on pregnancy outcomes in women with subclinical hypothyroidism and thyroid autoimmuneity undergoing in vitro fertilization/intracytoplasmic sperm injection: an updated meta-analysis of randomized controlled trials

BACKGROUND

Evidence suggests that subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI) are associated with adverse pregnancy outcomes. This systematic review and meta-analysis was conducted to determine whether levothyroxine (LT4) supplementation would improve pregnancy outcomes among infertile women with SCH and/or TAI who underwent in vitro fertilization (IVF) or intracytoplastic sperm injection (ICSI).

METHODS

We searched databases of PubMed, EMBASE, Web of Science, Cochrane Controlled Trials Register databases, and Clinicaltrials.gov up to April 2018 to identify eligible studies. Studies that focused on the treatment effect of LT4 on pregnancy outcomes of women with SCH and/or TAI who underwent IVF/ICSI were included in the data synthesis. We only included randomized controlled trials (RCTs). Relative risks (RR) and 95% confidence intervals (CI) were calculated using a random-effects model to assess the results of pregnancy outcomes, including clinical pregnancy rate, miscarriage rate, live birth rate and preterm birth rate.

RESULTS

Four published RCTs including 787 infertile couples undergoing IVF/ICSI were included in this meta-analysis. Notably, the study observed no significant associations of LT4 treatment with the clinical pregnancy rate (RR = 1.46, 95% CI: 0.86-2.48), live birth rate (RR = 2.05, 95% CI: 0.96-4.36), or preterm birth rate (RR = 1.13, 95% CI: 0.65-1.96). However, patients receiving LT4 supplementation had a significantly decreased miscarriage rate relative to those receiving a placebo or no treatment (RR = 0.51, 95% CI: 0.32-0.82). A further sub-group analysis showed that LT4 supplementation did not improve the miscarriage rates among patients with SCH (RR = 0.67, 95% CI: 0.39-1.15) or TAI (RR = 0.28, 95% CI: 0.07-1.06).

CONCLUSIONS

Given its potential to reduce the miscarriage rate, LT4 supplementation is recommended for infertile women with SCH and/or TAI who are undergoing IVF/ICSI. However, additional population-based RCTs are needed to confirm this recommendation.

In vitro fertilization/intracytoplasmic insemination and thyroid function: reviewing the evidence

Recent findings, that specific G protein-coupled TSH receptors (TSHR) and the nuclear thyroid hormone receptors (THRs) are widely expressed in reproductive tissues, reveal the close links between hypothalamus-pituitary-thyroid and hypothalamus-pituitary-gonadal axes. It has been suggested that thyroid function as well as thyroid autoimmunity (TAI) have an impact on Assisted Reproduction Technology (ART) reproductive outcome. Lately, it became evident that ovarian stimulation (OS) may also have an impact on thyroid function. This narrative review describes the mutual interaction between thyroid function and OS, by reviewing the current evidence, assessing the pathophysiological links and arriving at practical recommendations.

The association of maternal thyroid function with placental hemodynamics

STUDY QUESTION

What is the clinical association of maternal thyroid function with placental hemodynamic function?

SUMMARY ANSWER

A higher free thyroxine (FT4) concentration in early pregnancy is associated with higher placental vascular resistance.

WHAT IS KNOWN ALREADY

Suboptimal placental function is associated with preeclampsia (which, in turn, further deteriorates placental hemodynamics and impairs the fetal blood supply), fetal growth restriction and premature delivery. Studies have suggested that thyroid hormone (TH) has a role in placental development through effects on trophoblast proliferation and invasion.

STUDY DESIGN, SIZE, DURATION

This study was embedded in The Generation R cohort, a population-based prospective study from early fetal life onwards in Rotterdam, the Netherlands. In total, 7069 mothers with expected delivery date between April 2002 and January 2006 were enrolled during early pregnancy.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) concentrations were measured during early pregnancy (median 13.4 weeks, 95% range 9.7-17.6 weeks). Placental function was assessed by Doppler ultrasound via measurement of arterial vascular resistance, i.e. umbilical artery pulsatility index (PI) and uterine artery resistance index (RI) (both measured twice, between 18-25th and after 25th gestational weeks) and the presence of uterine artery notching (once after the 25th gestational week) in 5184 pregnant women.

MAIN RESULTS AND THE ROLE OF CHANCE

FT4 was positively linearly associated with umbilical artery PI in the second and third trimesters as well as with uterine artery RI in the second trimester and the risk of uterine artery notching in the third trimester (P < 0.05 for all). The association of thyroid function with preeclampsia and birth weight was partially mediated through changes in placental function, with the percentages of mediated effects being 10.4% and 12.5%, respectively.

LIMITATIONS, REASONS FOR CAUTION

A potential limitation is the availability of only a single time point for TH measurements and different numbers of missing placental ultrasound measurements for the adverse outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

A higher FT4 concentration in early pregnancy is associated with higher vascular resistance in the second and third trimesters in both the maternal and fetal placental compartment. These effects on placental function might explain the association of FT4 with adverse pregnancy outcomes, including preeclampsia and fetal growth restriction.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a fellowship from ERAWEB, a project funded by the European Commission (to M.B.) and by clinical fellowship from The Netherlands Organization for Health Research and Development (ZonMw), Project 90700412 (to R.P.P.). The authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.