Thyroid hormone alteration in pre-eclamptic women

Association of thyroid function test abnormalities with preeclampsia: a systematic review and meta-analysis

BACKGROUND

Preeclampsia is a life-threatening disorder during pregnancy and postpartum periods. Preeclampsia can affect the activity of many organs. It is very important because if this disorder is associated with changes in thyroid function, it can affect the results of maternal and fetal tests. Accordingly, the aim of this meta-analysis study was to assess the abnormalities in thyroid function tests in preeclampsia.

METHODS

Studies were selected through a systematic search of the MEDLINE/PubMed, Scopus, Web of Science Core Collection, and Google Scholar databases in 31st August 2021. Also, reference lists of review articles and relevant studies were manual-searched to identify other potentially eligible studies. English studies that compared TSH, T4 and T3 of normal pregnant with preeclamptic women (Known to be normotensive before pregnancy; gestational age 20 week or more; singleton pregnancy; no previous history of thyroid dysfunction) were screened. Data sets were screened for eligibility by two independent reviewers. Articles were assessed by the Newcastle-Ottawa Scale. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used for quality assessment of evidence on outcome levels.

RESULTS

After reviewing 886 published studies, 63 observational studies were selected and used for this meta-analysis. The study population included 21,528 pregnant women. The findings revealed that TSH (SMD = 1.70, 95%CI: 1.39 to 2.02; p < 0.001) was significantly higher in preeclamptic women. TT4 (SMD = -0.82, 95%CI: -1.16, -0.49; p < 0.001), TT3 (SMD = -0.88, 95%CI: -1.36 to -0.41; p < 0.001) and FT3 (SMD = -0.59, 95%CI: -0.91 to -0.27; p < 0.001) were less in preeclamptic women. There was no statistically significant difference in FT4 between two groups (SMD = 0.002, 95%CI: -0.27 to 0.27; p = .990). The results of publication bias and sensitivity analysis confirmed the reliability and stability of this meta-analysis. The quality of evidence was regarded as moderate, low, and very low for these risk factors according to the GRADE approach.

CONCLUSIONS

Findings of this meta-analysis indicated preeclamptic women were more at risk of changes in thyroid function tests. In order to prevent thyroid disorders, it is recommended that thyroid function tests be performed in women with pre-eclampsia.

Endocrine disrupting chemicals (EDCs) and placental function: Impact on fetal brain development

Pregnancy is a critical time of vulnerability for the development of the fetal brain. Exposure to environmental pollutants at any point in pregnancy can negatively impact many aspects of fetal development, especially the organization and differentiation of the brain. The placenta performs a variety of functions that can help protect the fetus and sustain brain development. However, disruption of any of these functions can have negative impacts on both the pregnancy outcome and fetal neurodevelopment. This review presents current understanding of how environmental exposures, specifically to endocrine disrupting chemicals (EDCs), interfere with placental function and, in turn, neurodevelopment. Some of the key differences in placental development between animal models are presented, as well as how placental functions such as serving as a xenobiotic barrier and exchange organ, immune interface, regulator of growth and fetal oxygenation, and a neuroendocrine organ, could be vulnerable to environmental exposure. This review illustrates the importance of the placenta as a modulator of fetal brain development and suggests critical unexplored areas and possible vulnerabilities to environmental exposure.

Biological functions of thyroid hormone in placenta

The thyroid hormone, 3,3,5-triiodo-l-thyronine (T₃), modulates several physiological processes, including cellular growth, differentiation, metabolism, inflammation and proliferation, via interactions with thyroid hormone response elements (TREs) in the regulatory regions of target genes. Infection and inflammation are critical processes in placental development and pregnancy-related diseases. In particular, infection is the leading cause of neonatal mortality and morbidity worldwide. However, to date, no successful approach has been developed for the effective diagnosis of infection in preterm infants. Pre-eclampsia (PE) is a serious disorder that adversely affects ~5% of human pregnancies. Recent studies identified a multiprotein complex, the inflammasome, including the Nod-like receptor (NLR) family of cytosolic pattern recognition receptors, the adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1, which plays a vital role in the placenta. The thyroid hormone modulates inflammation processes and is additionally implicated in placental development and disease. Therefore, elucidation of thyroid hormone receptor-regulated inflammation-related molecules, and their underlying mechanisms in placenta, should facilitate the identification of novel predictive and therapeutic targets for placental disorders. This review provides a detailed summary of current knowledge with respect to identification of useful biomarkers and their physiological significance in placenta.

Genetics in endocrinology: genetic variation in deiodinases: a systematic review of potential clinical effects in humans

Iodothyronine deiodinases represent a family of selenoproteins involved in peripheral and local homeostasis of thyroid hormone action. Deiodinases are expressed in multiple organs and thyroid hormone affects numerous biological systems, thus genetic variation in deiodinases may affect multiple clinical endpoints. Interest in clinical effects of genetic variation in deiodinases has clearly increased. We aimed to provide an overview for the role of deiodinase polymorphisms in human physiology and morbidity. In this systematic review, studies evaluating the relationship between deiodinase polymorphisms and clinical parameters in humans were eligible. No restrictions on publication date were imposed. The following databases were searched up to August 2013: Pubmed, EMBASE (OVID-version), Web of Science, COCHRANE Library, CINAHL (EbscoHOST-version), Academic Search Premier (EbscoHOST-version), and ScienceDirect. Deiodinase physiology at molecular and tissue level is described, and finally the role of these polymorphisms in pathophysiological conditions is reviewed. Deiodinase type 1 (D1) polymorphisms particularly show moderate-to-strong relationships with thyroid hormone parameters, IGF1 production, and risk for depression. D2 variants correlate with thyroid hormone levels, insulin resistance, bipolar mood disorder, psychological well-being, mental retardation, hypertension, and risk for osteoarthritis. D3 polymorphisms showed no relationship with inter-individual variation in serum thyroid hormone parameters. One D3 polymorphism was associated with risk for osteoarthritis. Genetic deiodinase profiles only explain a small proportion of inter-individual variations in serum thyroid hormone levels. Evidence suggests a role of genetic deiodinase variants in certain pathophysiological conditions. The value for determination of deiodinase polymorphism in clinical practice needs further investigation.

Metabolic dysfunctions in Nigerian pre-eclamptics

AIM

The patho-physiology of pre-eclampsia is not fully understood. This study determined the plasma levels of markers of oxidative stress, thyroid hormones, nitric oxide, C-reactive protein, and nutritional profiles in pre-eclamptic patients.

METHODS

Thirty-two pregnant women with pre-eclampsia and 40 women with normal pregnancy (controls) participated in this study. The pre-eclamptics were recruited after 20 weeks of gestation. They presented with hypertension (systolic pressure = 169 ± 26.0 mmHg, diastolic pressure = 102 ± 11.0 mmHg), significant proteinuria (368 ± 39 mg/24 h), severe headache, abdominal pain and vomiting. The plasma levels of total antioxidant potential (TAP), total plasma peroxides (TPP), total cholesterol (TC), total protein (TP), albumin, globulin, nitric oxide (NO), C-reactive protein (CRP), total tri-iodotyronine (TT3) and thyroid stimulating hormone (TSH) were determined in them using spectrophotometry, radial immunodiffusion and enzyme linked immunosorbent assay (ELISA) methods, respectively. Oxidative stress index (OSI) was calculated as the percent ratio of TPP and TAP.

RESULTS

The weight and body mass index of pre-eclamptics increased significantly (p < 0.05) when compared with the controls. The mean systolic and diastolic blood pressure increased significantly (p < 0.001) in pre-eclamptics when compared with the controls. Plasma mean values of TAP, NO, albumin, TP and TT3 decreased significantly (p < 0.05) in pre-eclamptics when compared with the controls. The plasma mean values of TSH, TPP, OSI, CRP, and TC increased significantly (p < 0.05) in pre-eclamptics when compared with the controls. There was no significant change in the plasma value of globulin when compared with the controls. TT3 correlated positively with plasma TP and globulin in the pre-eclamptics.

CONCLUSION

It could be concluded that hypothyroidism, hypercholesterolemia, oxidative stress and deranged inflammatory responses are possible features of pre-eclampsia.

Thyroid dysfunction and autoantibodies association with hypertensive disorders during pregnancy

Background. Thyroid dysfunction and autoimmunity are relatively common in reproductive age and have been associated with adverse health outcomes for both mother and child, including hypertensive disorders during pregnancy. Objective. To survey the relation between thyroid dysfunction and autoimmunity and incidence and severity of pregnancy-induced hypertensive disorders. Method. In this case control study 48 hypertensive patients in 4 subgroups (gestational hypertension, mild preeclampsia, severe preeclampsia, eclampsia) and 50 normotensive ones were studied. The samples were nulliparous and matched based on age and gestational age and none of them had previous history of hypertensive or thyroid disorders and other underlying systemic diseases or took medication that might affect thyroid function. Their venous blood samples were collected using electrochemiluminescence and ELISA method and thyroid hormones and TSH and autoantibodies were measured. Results. Hypertensive patients had significant lower T3 concentration compared with normotensive ones with mean T3 values 152.5 ± 48.93 ng/dL, 175.36 ± 58.07 ng/dL respectively. Anti-TPO concentration is higher in control group 6.07 ± 9.02 IU/mL compared with 2.27 ± 2.94 IU/mL in cases. Conclusion. The severity of preeclampsia and eclampsia was not associated with thyroid function tests. The only significant value was low T3 level among pregnancy, induced hypertensive patients.

The effect of the D1-C785T polymorphism in the type 1 iodothyronine deiodinase gene on the circulating thyroid hormone levels in Romanian women with preeclampsia. Association with the degree of severity and pregnancy outcome of preeclampsia

AIM

To investigate the biochemical and genetic thyroid status in women with preeclampsia by the determination of serum FT3 and FT4 levels in association with D1-C785T genotypes.

METHODS

We genotyped using PCR-RFLP methods 50 women with preeclampsia and 50 normotensive pregnant women.

RESULTS

FT3 levels (pg/ml, 2.63 ± 0.56 vs. 2.91 ± 1.41) were low, and FT4 levels (ng/dl, 1.11 ± 0.3 vs. 0.88 ± 0.14) were high in women with preeclampsia compared to normal pregnant women. The association with severe preeclampsia was stronger for the homozygous T/T genotype (OR 6.57, p = 0.029). Women with preeclampsia with the D1-T785 mutated allele had lower FT3 levels (pg/ml, 2.31 ± 0.81 vs. 3.04 ± 0.39, p < 0.001), higher FT4 levels (ng/dl, 1.32 ± 0.87 vs. 0.84 ± 0.24, p = 0.009) than women with preeclampsia with the D1-C/C genotype. Significant decrease in serum FT3 levels in positive women with severe preeclampsia compared to women negative for this genetic variation (pg/ml, 1.59 ± 0.74 vs. 2.77 ± 0.23, p = 0.003) was observed. Women with severe preeclampsia, positive for the mutated T785 allele, delivered at a significantly lower gestational age (31.75 ± 3.69 vs. 38.66 ± 3.21 weeks, p = 0.035) neonates with a lower birth weight (1861.11 ± 869.9 vs. 3500 ± 424.26 g, p = 0.023) compared to women negative for the same allele.

CONCLUSIONS

Thyroid hormone levels and the D1-C785T polymorphism, alone or in combination, correlate with the severity of preeclampsia. The D1-C785T polymorphism influences the outcome of pregnancy in severe preeclampsia.

Correlation between the TSHRc-Asp727Glu polymorphism and plasma thyroid stimulating hormone levels in Romanian preeclamptic women

AIM

To analyze the influence of thyroid stimulating hormone (TSH) levels and/or the Asp727Glu polymorphism on the severity and perinatal outcome of preeclampsia.

METHODS

Forty-nine women with preeclampsia and 58 normal pregnant women were genotyped for the TSHRc-Asp727Glu polymorphism using PCR-RFLP methods. The plasma TSH levels were measured by ELISA method.

RESULTS

Fourteen (77.78%) women of 18 pregnant women with abnormal TSH levels had preeclampsia compared to 35 (39.33%) of 89 pregnant women with normal TSH levels who had preeclampsia (OR 5.4, p = 0.003). The mean TSH levels were 2.13 ± 1.44 μU/ml, 2.47 ± 2.03 μU/ml and 4.27 ± 2.75 μU/ml in women with pregnancy induced hypertension (PIH), mild and severe preeclampsia, respectively. OR for PIH and mild preeclampsia was 1.08 (p = 1) and 9.45 (p = 0.06), respectively, in association with the Asp/Asp genotype. All women with severe preeclampsia had the Asp/Asp genotype. The risk for preeclampsia in association with TSH > 4 μU/ml and Asp/Asp genotype is 20.8 (p < 0.01). Preeclamptic women with TSH levels > 4 μU/ml and the Asp/Asp genotype delivered earlier (weeks, 34.92 ± 4.33 vs. 36.6 ± 3.21, p = 0.3) neonates with lower birth weight (grams, 2361.54 ± 1155.81 vs. 3000 ± 1072.38, p = 0.3) than preeclamptic women with TSH levels  < 4 μU/ml and the Asp/Glu genotype.

CONCLUSIONS

Higher TSH levels and/or the TSHRc-Asp727Glu polymorphism represent risk factors for preeclampsia and could be correlated with the severity of preeclampsia.

Maternal thyroid function at 11 to 13 weeks of gestation and subsequent development of preeclampsia

OBJECTIVE

To determine if maternal thyroid function in the first trimester is altered in pregnancies that subsequently develop preeclampsia (PE).

METHODS

Mean arterial pressure (MAP), uterine artery pulsatility index (PI) maternal serum thyroid stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) at 11 to 13 weeks of gestation were measured in 102 singleton pregnancies that subsequently developed PE, and the values were compared to the results of 4318 normal pregnancies.

RESULTS

In both the PE groups that required delivery before 34 weeks (early-PE) and the late-PE group, compared with the unaffected group, the median MAP multiple of the normal median (MoM) and uterine artery PI MoM were significantly increased. In late-PE but not in early-PE, compared with the unaffected group, the median TSH MoM was significantly increased and the median FT4 MoM was decreased. Logistic regression analysis demonstrated that TSH MoM provided a significant contribution in the prediction of late-PE.

CONCLUSION

Impaired thyroid function may predispose to the development of late-PE, and measurement of maternal serum TSH can improve the prediction of late-PE provided by a combination of factors in the maternal history and the measurements of MAP and uterine artery PI.

Thyroid profile of term appropriate for gestational age neonates in Nigeria: a forerunner to screening for congenital hypothyroidism

Thyroid hormones in normal quantity are vital for physical growth and mental development during fetal and postnatal life. The available publications in Sub-Saharan Africa on the thyroid function of newborn infants was reported in babies delivered in moderate to severe goitre zones; utilizing the hormone levels from these studies may have a measure of bias. Newborn screening for congenital hypothyroidism (CH) in Sub-Saharan Africa is still a mirage, the technicality of the best timing for collection of blood samples need to be studied. Consequently, we report the serum levels of total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) at birth and at 72 h after birth, and to ascertain if there is any significant difference between them. This was a prospective cross-sectional study (6 months period) between November and April 2005. One hundred and fourteen apparently healthy term AGA neonates had their thyroid function analyzed, the females (59) were slightly more in number than the (males 55). Most of them were between GA of 37-38 weeks at birth. The observed 72 h mean values of serum T3 and T4 (1.06 and 101.38 nmol l(-1)) compared with the cord values at birth (0.89 and 75.48 nmol l(-1)), was not statistically significant. The mean cord TSH levels (13.59 mU l(-1)) compared with 72 h serum TSH levels (10.25 mU l(-1)) was also insignificant p = 0.3. For Sub-Saharan Africa cord TSH analysis may be a reasonable choice for newborn screening for congenital hypothyroidism.

Pre-eclampsia, soluble fms-like tyrosine kinase 1, and the risk of reduced thyroid function: nested case-control and population based study

OBJECTIVE

To determine if pre-eclampsia is associated with reduced thyroid function during and after pregnancy.

DESIGN

Nested case-control study during pregnancy and population based follow-up study after pregnancy.

SETTING

Calcium for Pre-eclampsia Prevention trial of healthy pregnant nulliparous women in the United States during 1992-5, and a Norwegian population based study (Nord-Trondelag Health Study or HUNT-2) during 1995-7 with linkage to the medical birth registry of Norway.

PARTICIPANTS

All 141 women (cases) in the Calcium for Pre-eclampsia Prevention trial with serum measurements before 21 weeks' gestation (baseline) and after onset of pre-eclampsia (before delivery), 141 normotensive controls with serum measurements at similar gestational ages, and 7121 women in the Nord-Trondelag Health Study whose first birth had occurred in 1967 or later and in whom serum levels of thyroid stimulating hormone had been subsequently measured.

MAIN OUTCOME MEASURES

Thyroid function tests and human chorionic gonadotrophin and soluble fms-like tyrosine kinase 1 concentrations in the Calcium for Pre-eclampsia Prevention cohort and odds ratios for levels of thyroid stimulating hormone above the reference range, according to pre-eclampsia status in singleton pregnancies before the Nord-Trondelag Health Study.

RESULTS

In predelivery specimens of the Calcium for Pre-eclampsia Prevention cohort after the onset of pre-eclampsia, thyroid stimulating hormone levels increased 2.42 times above baseline compared with a 1.48 times increase in controls. The ratio of the predelivery to baseline ratio of cases to that of the controls was 1.64 (95% confidence interval 1.29 to 2.08). Free triiodothyronine decreased more in the women with pre-eclampsia than in the controls (case ratio to control ratio 0.96, 95% confidence interval 0.92 to 0.99). The predelivery specimens but not baseline samples from women with pre-eclampsia were significantly more likely than those from controls to have concentrations of thyroid stimulating hormone above the reference range (adjusted odds ratio 2.2, 95% confidence interval 1.1 to 4.4). Both in women who developed pre-eclampsia and in normotensive controls the increase in thyroid stimulating hormone concentration between baseline and predelivery specimens was strongly associated with increasing quarters of predelivery soluble fms-like tyrosine kinase 1 (P for trend 0.002 and <0.001, respectively). In the Nord-Trondelag Health Study, women with a history of pre-eclampsia in their first pregnancy were more likely than other women (adjusted odds ratio 1.7, 95% confidence interval 1.1 to 2.5) to have concentrations of thyroid stimulating hormone above the reference range (>3.5 mIU/l). In particular, they were more likely to have high concentrations of thyroid stimulating hormone without thyroid peroxidase antibodies (adjusted odds ratio 2.6, 95% confidence interval 1.3 to 5.0), suggesting hypothyroid function in the absence of an autoimmune process. This association was especially strong (5.8, 1.3 to 25.5) if pre-eclampsia had occurred in both the first and the second pregnancies.

CONCLUSION

Increased serum concentration of soluble fms-like tyrosine kinase 1 during pre-eclampsia is associated with subclinical hypothyroidism during pregnancy. Pre-eclampsia may also predispose to reduced thyroid function in later years.

The gonadotropins: tissue-specific angiogenic factors?

The gonadotropins, whose members are human chorionic gonadotropin (hCG), lutenizing hormone (LH) and follicle-stimulating hormone (FSH) are a well characterized hormone family known to regulate reproductive functions in both females and males. Recent studies indicate that they can modulate the vascular system of reproductive organs. It was shown that gonadotropins not only influence the expression of vascular endothelial growth factor (VEGF) and both its receptors VEGFR-1 and -2, but also modulate other ubiquitously expressed angiogenic factors like the angiopoietins and their receptor Tie-2, basic fibroblast growth factor or placental-derived growth factor. Some recent data indicates a possible direct action of gonadotropins on endothelial cells. Thus, the gonadotropins act as tissue-specific angiogenic factors providing an optimal vascular supply during the menstrual cycle and early pregnancy in the female reproductive tract as well as in testis. In pathological conditions (e.g. preeclampsia, intrauterine growth restriction, ovarian hyperstimulation or endometriosis), these tightly regulated interactions between the gonadotropins and the ubiquitous angiogenic factors appear to be disturbed. The intent of this short manuscript is to review the current knowledge of the regulatory role of the gonadotropins in vasculo- and angiogenesis. We also review angiogenic actions of thyroid-stimulating hormone (TSH), a glycoprotein closely related to gonadotropins, which display strong gonodal actions.

Thyroid disorders in pregnancy

PURPOSE OF REVIEW

There is now increasing understanding of the association between not only overt, but also subclinical, thyroid disorders and dysfunction with adverse reproductive outcome. In particular, hypothyroidism and thyroid autoimmunity disorders have been shown to have both short- and long-term consequences on mother and child. An updated review is merited to revise many of the traditional views on thyroid disorders in pregnancy.

RECENT FINDINGS

Thyroid disorders constitute the commonest group of pre-gestational endocrine disorders found in pregnant women. In mothers taking antithyroid medications, breastfeeding is considered safe. The relatively high prevalence of hypothyroidism, especially subclinical hypothyroidism, the significance of screening and treatment, and the roles of iodine insufficiency and thyroid antibodies on the outcome of pregnancy and long-term neurological development of the offspring have been documented. In hypothyroid women, the dose of thyroxine replacement often needs to be adjusted from as early as the first trimester to maintain an adequate circulating thyroxine concentration.

SUMMARY

Apart from overt hyperthyroidism and hypothyroidism diagnosed before and during pregnancy, biochemical abnormalities or evidence of thyroid autoimmunity in clinically euthyroid women can affect both obstetric outcome and long-term neurological development of the offspring. Screening for thyroid function and autoimmunity, and timely and appropriate treatment, will improve pregnancy outcome. The thyroid function of infants born to mothers with thyroid disorders should also be assessed as serial monitoring and treatment may be necessary.