Relationship Between Subclinical Hypothyroidism in Pregnancy and Hypertensive Disorder of Pregnancy: A Systematic Review and Meta-Analysis

Pregnancy outcome in subclinical hypothyroidism with and without thyroid peroxidase antibodies-a prospective cohort study

BACKGROUND

Subclinical hypothyroidism (SCH) in pregnancy is associated with adverse foetomaternal outcomes. The literature is scarce with respect to maternal and perinatal outcomes in women with mild SCH (TSH levels between 2.5-4 mIU/L).

OBJECTIVES

The primary objective of the study was to compare the pregnancy outcome between SCH and euthyroid women. The secondary objectives were to find out the proportion of women with SCH having thyroid peroxidase antibodies (TPOAb) and to see the effect of TPOAb positivity on foetomaternal outcomes.

MATERIALS AND METHODS

A total of 178 pregnant women were recruited in the first trimester, and those with TSH between 0.1 and 2.4 mIU/L were considered as euthyroid and 2.5-4mIU/L were labelled as SCH. Women with SCH underwent testing for TPOAb. All women were followed until delivery, and foetomaternal outcomes were assessed.

RESULTS

Amongst SCH group, there was a significantly higher proportion of overweight and obese women (76/91 (83.51%) vs 59/87 (68%), p = 0.031). The neonatal intensive care unit (NICU) admission was higher with adjusted odds ratio of 3.24 (1.41-7.43) in women with SCH as compared to euthyroid women. Otherwise, there was no difference in foetomaternal outcomes between the two groups. The proportion of gestational diabetes mellitus, intrauterine growth retardation and still birth were higher in SCH women with TPOAb as compared to euthyroid. Amongst SCH women, the proportion of induced labour was lower (aOR:0.27 (0.08-0.93) whereas the proportion of stillbirth and low APGAR scores were higher in TPOAb-positive women with a statistically significant difference and adjusted odds ratio (aOR:20.18 (1.84-220.83)) and (aOR:4.77 (1.06-21.3)), respectively, when compared to TPOAb-negative women.

CONCLUSION

There appears to be no difference in pregnancy outcomes between women with SCH and euthyroid women except higher NICU admission in SCH group. Future multi-centre large prospective studies are required to understand better about the pregnancy outcomes in these women.

Genome-wide association studies of thyroid-related hormones, dysfunction, and autoimmunity among 85,421 Chinese pregnancies

Maintaining normal thyroid function is crucial in pregnancy, yet thyroid dysfunction and the presence of thyroid peroxidase antibodies (TPOAb) affect 0.5% to 18% of pregnant women. Here, we conducted a genome-wide association study (GWAS) of eight thyroid traits, including two thyroid-related hormones, four thyroid dysfunctions, and two thyroid autoimmunity measurements among 85,421 Chinese pregnant women to investigate the genetic basis of thyroid function during pregnancy. Our study identified 176 genetic loci, including 125 previously unknown genome-wide associations. Joint epidemiological and Mendelian randomization analyses revealed significant associations between the gestational thyroid phenotypes and gestational complications, birth outcomes, and later-age health outcomes. Specifically, genetically elevated thyroid-stimulating hormone (TSH) levels during pregnancy correlated with lower glycemic levels, reduced blood pressure, and longer gestational duration. Additionally, TPOAb and thyroid functions during pregnancy share genetic correlations with later-age thyroid and cardiac disorders. These findings provide insights into the genetic determinants of thyroid traits during pregnancy, which may lead to new therapeutics, early pre-diagnosis and preventive strategies starting from early adulthood.

Development, Validation and Clinical Utility of a Risk Prediction Model for Maternal and Neonatal Adverse Outcomes in Pregnant Women with Hypothyroidism

Purpose

This study aimed to create, verify and assess the clinical utility of a prediction model for maternal and neonatal adverse outcomes in pregnant women with hypothyroidism.

Methods

A prediction model was developed, and its accuracy was tested using data from a retrospective cohort. The study focused exclusively on female patients diagnosed with hypothyroidism who were admitted to a tertiary hospital. The development and validation cohort comprised individuals who gave birth between 1 October 2020 and 31 December 2022. The primary outcome was a combination of crucial maternal and newborn problems (eg premature births, abortions and neonatal asphyxia). The prediction model was developed using logistic regression. Evaluation of the model's performance was conducted based on its ability to discriminate, calibrate and provide clinical value.

Results

In total, nine variables were chosen to develop the predictive model for adverse maternal and neonatal outcomes during pregnancy with hypothyroidism. The area under the curve of the model for predicting maternal adverse outcomes was 0.845, and that for predicting neonatal adverse outcomes was 0.685. The calibration plots showed good agreement between the nomogram predictions and the actual observations in both the training and validation cohorts. Furthermore, decision curve analysis suggested that the nomograms were clinically useful and had good discriminative power to identify high-risk mother-infant cases.

Conclusion

Two models to predict the risk probability of maternal and neonatal adverse outcomes in pregnant women with hypothyroidism were developed and verified to assist physicians in evaluating maternal and neonatal adverse outcomes throughout pregnancy with hypothyroidism and to facilitate decision-making regarding therapy.

Update on therapeutic use of levothyroxine for the management of hypothyroidism during pregnancy

Hypothyroidism is a relatively common finding during pregnancy. This may be due either to the presence of existing thyroid disease and/or to the increased demands that pregnancy places the thyroid gland to provide thyroid hormones for the mother and the developing fetus. There is no doubt that overt hypothyroidism is associated strongly with adverse pregnancy outcomes, including miscarriage. Meta-analyses show that thyroid hormone replacement with levothyroxine (LT4) reduces the risk of adverse pregnancy outcomes in the setting of overt hypothyroidism. Accordingly, management guidelines in this area are unanimous in recommending intervention with to control the level of thyrotropin (TSH) to below 2.5 μIU/mL. The evidence for an adverse impact of subclinical hypothyroidism (SCH) on pregnancy outcomes is less clear, although meta-analyses suggest that SCH reduces the chance of a successful pregnancy outcome. Guidelines also support intervention for some patients with SCH, particularly where TSH is high (>10 μIU/mL), or where TSH is above its trimester-specific reference range in a woman with thyroid autoimmunity (giving LT4 to euthyroid women with thyroid autoimmunity is not supported). Real-world evidence suggests that hypothyroidism in pregnancy is often overlooked or that LT4 is not given appropriately to gain tight control of TSH. More research is needed to identify the barriers to optimal thyroid care with LT4 at this crucial time.

Optimizing levothyroxine treatment for subclinical hypothyroidism during pregnancy

The onset of pregnancy places additional stress of the thyroid gland, which must produce additional thyroid hormones to support the developing foetus. Hypothyroidism, including subclinical hypothyroidism (SCH), may appear de novo at this time, or existing thyroid disease may become more severe. Accordingly, SCH is a relatively common complication of up to about 3% of pregnancies, with higher rates in some areas. There is strong evidence from systematic reviews and meta-analyses that uncontrolled SCH is associated with an increased risk of adverse pregnancy outcomes, including miscarriage, preeclampsia, and gestational diabetes. The evidence base also suggests that treatment with levothyroxine (LT4), optimized to control thyrotropin (TSH) to within its pregnancy-specific reference ranges reduces these risks. Current management guidelines provide a clear framework of intervention with LT4 in pregnant women with SCH, especially where TSH is high or where thyroperoxidase autoantibodies are present. Sub-optimal adherence to LT4 is common: it is important that patients take their LT4 correctly and that treating physicians and/or healthcare professionals manage these patients according to the latest management guidelines. The titration of LT4 is likely to occur within a range of LT4 daily doses between 25 µg and 75 µg for the majority of this population. LT4 is a narrow therapeutic index drug and small variations in dosage may produce a clinically significant change in thyroid status. Newer formulations of LT4, engineered to provide more precise and consistent dosing, and with a broad range of tablet strengths, may facilitate the precise titration of the LT4 dose for these patients.

Early treatment will prevent feto-maternal complications in thyroid disorders during pregnancy: A prospective study

Context

Associations between adverse maternal complications and fetal outcomes are known entity in thyroid disorders during pregnancy. Thus, prompt identification of thyroid disorders and timely initiation of treatment is essential. Universal screening and early treatment of pregnant women for thyroid disorder should be considered especially in a resource-limited country like India with a high prevalence of undiagnosed thyroid disorders and adverse feto-maternal outcomes.

Aims

Early treatment will prevent feto-maternal complications in thyroid disorders in pregnant females visiting outpatient department in tertiary care hospital in rural settings.

Settings and Design

This study was conducted in a tertiary care rural-based medical college with participation from departments of Obstetrics and Gynaecology, Medicine, and ENT.

Methods and Material

Expectant mothers in first trimester who had urine pregnancy test positive in outpatient clinic were included after a written informed consent. Detailed history and examination was done. TSH was done if abnormal-FT3 and FT4 were done. All thyroid disorders were treated according to American Thyroid Association (ATA) 2017 guideline. All pregnancies were followed up for maternal complications and fetal outcomes.

Statistical Analysis Used

Data from the performa were entered in Office Excel and analysis was performed using STATA (14.2). Descriptive statistics (mean [standard deviation], Frequency [%], etc.) were used to depict profile of study participants, prevalence of thyroid dysfunction, and outcome measures. Chi-square test was employed to assess the association between thyroid dysfunction and various maternal and fetal outcomes. A P value less than. 05 was considered statistically significant.

Results

Of 350 pregnant females, 83 (23.5%) pregnant females had thyroid disorder. Of which, 33 (9.4%) had subclinical hypothyroidism, 37 (10.5%) had overt hypothyroidism, 11 (3.1%) had subclinical hyperthyroidism, and two (0.5%) had hyperthyroidism. The prevalence of hypothyroidism in pregnancy increases with increasing age (P value. 001) and not associated with parity, abortion, and consumption of iodized salt. Total patients with feto-maternal outcome follow-up were 241. Pre-eclampsia (P value. 004) was a significant complication in hypothyroid mothers. There was no significant difference in the rate of cesarean section and preterm delivery in hypothyroid and euthyroid mothers. Neonatal outcomes showed more trends of abortion, fetal demise, and IUFD in the hypothyroid group, although not statistically significant. (P value. 07).

Conclusions

Due to the high prevalence of thyroid disorders during pregnancy, universal screening of thyroid disorders should be done in early pregnancy instead of high-risk screening. Early detection and early treatment in the first 10 weeks of pregnancy help to prevent maternal and fetal complications of thyroid disorders in pregnancy. Pre-eclampsia is to be monitored in treated pregnant females with hypothyroidism.

Prevalence, risk factors, and consequences of hypothyroidism among pregnant women in the health region of Lleida: A cohort study

BACKGROUND

Primary maternal hypothyroidism is defined as the increase of TSH levels in serum during pregnancy. Hypothyroidism in pregnancy is the second most common endocrine disease, after diabetes mellitus, with a prevalence ranging between 3.2 and 5.5%. Its variability depends on ethnical differences. Hypothyroidism in pregnancy is associated with other chronic diseases and fetal and maternal outcomes.

OBJECTIVE

To analyze the prevalence of hypothyroidism among multiethnic pregnant women, and to evaluate the comorbidity with chronic diseases and outcomes leaded during pregnancy and newborn.

METHODS

Retrospective observational cohort study in pregnant women during the years 2012-2018 in the health region of Lleida. The relationship of hypothyroidism with different variables was analyzed by calculating the adjusted odds ratio (aOR) and the 95% confidence intervals (CI) with multivariate logistic regression models.

RESULTS

We analyzed a sample of 17177 pregnant women, which represents more than 92% of the total of pregnant women in the health region of Lleida. The annual prevalence of hypothyroidism was 5.7-7.1%. According to the region of origin, the lowest prevalence was found in the population from Sub Saharian Africa (2.1%), while the highest was from Asia and the Middle East (8.6%). Other factors associated with hypothyroidism were age, hypertension, diabetes mellitus, and dyslipidemia. In addition, we did not observe an effect of hypothyroidism on the course of pregnancy, childbirth, and on the newborn. Finally, there was a good control of the disease during pregnancy.

CONCLUSIONS

The prevalence of hypothyroidism in pregnancy was 6,5% in this study which depends on the country of origin, lower values were found in Sub Saharian African women and higher in those from Asia and the Middle East. Hypothyroidism was associated with age, diabetes mellitus, arterial hypertension, or dyslipidemia, and was not related to the Apgar score or the weight of the newborn.

Pre-pregnancy body mass index and glycated-hemoglobin with the risk of metabolic diseases in gestational diabetes: a prospective cohort study

Background

Metabolic diseases during pregnancy result in negative consequences for mothers. Pre-pregnancy body mass index (BMI) and late-pregnancy glycated-hemoglobin (HbA1c) are most important factors independently affecting the risk of gestational diabetes mellitus (GDM). However how both affect the combined risk of other metabolic diseases in women with GDM is unclear. The study aims to investigate the influence of pre-pregnancy BMI and pregnancy glycemic levels on other gestational metabolic diseases in women with GDM.

Methods

Pregnancies with GDM from January 2015 to December 2018 in the Xi'an longitudinal mother-child cohort study (XAMC) were retrospectively enrolled. Those without other metabolic diseases by the time of oral glucose tolerance test (OGTT) detection were finally recruited and divided into four groups by pre-pregnancy BMI (Underweight <18.5kg/m2; Normal weight 18.5-23.9 kg/m2; Overweight 24.0-27.9 kg/m2; Obesity ≥28.0 kg/m2, respectively) or two groups by HbA1c in late pregnancy (normal HbA1c<5.7%; high HbA1c≥5.7%). Multivariate logistic regression analysis was used to identify risk factors. Interaction between pre-pregnancy BMI (reference group 18.5-23.9 kg/m2) and HbA1c (reference group <5.7%) was determined using strata-specific analysis.

Results

A total of 8928 subjects with GDM were included, 16.2% of which had a composite of metabolic diseases. The pre-pregnancy overweight and obesity, compared with normal BMI, were linked to the elevated risk of the composite of metabolic diseases, particularly pre-eclampsia (both P <0.001) and gestational hypertension (both P <0.001). Meanwhile, patients with high HbA1c had an obvious higher risk of pre-eclampsia (P< 0.001) and gestational hypertension (P= 0.005) compared to those with normal HbA1c. In addition, there were significant interactions between pre-pregnancy BMI and HbA1c (P< 0.001). The OR of pre-pregnancy BMI≥ 28 kg/m2 and HbA1c≥ 5.7% was 4.46 (95% CI: 2.85, 6.99; P< 0.001). The risk of other metabolic diseases, except for pre-eclampsia (P= 0.003), was comparable between the two groups of patients with different HbA1c levels at normal pre-pregnancy BMI group. However, that was remarkably elevated in obese patients (P= 0.004), particularly the risk of gestational hypertension (P= 0.004).

Conclusion

Pre-pregnancy overweight/obesity and late-pregnancy high HbA1c increased the risk of other gestational metabolic diseases of women with GDM. Monitoring and controlling late-pregnancy HbA1c was effective in reducing metabolic diseases, particularly in those who were overweight/obese before conception.

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.

Subclinical hypothyroidism, outcomes and management guidelines: a narrative review and update of recent literature

Subclinical hypothyroidism (SCH) is diagnosed when serum thyroid stimulation hormone (thyrotropin; TSH) levels are above the reference range, accompanied by levels of free thyroxine within its reference range. The management of SCH remains a diagnostic and therapeutic challenge despite many years of research relating to its epidemiology, aetiology, effectiveness of treatment and safety. European Thyroid Association (ETA) guidelines for the management of SCH were published almost a decade ago. This narrative review summarizes the clinical literature relating to SCH and outcomes since the publication of these guidelines. Clinical evidence emerging during the previous decade generally supports the view that SCH is associated with adverse outcomes to an extent that is intermediate between euthyroidism and overt hypothyroidism although evidence that treatment with thyroid hormone replacement is beneficial is lacking. Accordingly, the rationale for the recommendations for intervention in the ETA guidelines based on the age of the patient, level of serum TSH, symptoms and comorbidities remains valid today.

Association between maternal thyroid function and risk of gestational hypertension and preeclampsia

OBJECTIVES

To investigate the influence of maternal level of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) one by one or in combination on incidence of gestational hypertension and preeclampsia.

METHODS

The study included pregnant women (n=107) hospitalized in the period from July 1, 2020 to October 10, 2021 at the Department of Pathology of Pregnancy of the University Clinic of Obstetrics and Gynecology, University Clinical Center Sarajevo (UCCS) (Bosnia and Herzegovina), due to hypertensive disorder in pregnancy without symptoms of impaired thyroid function. In all patients fulfilling inclusion criteria TSH, FT3, and FT4 using electrochemiluminescence immunoassay (ECLIA, Roche Diagnostics, Basel, Switzerland) were checked. There were two groups of patients: one with gestational hypertension (G1) and the other with preeclampsia (G2). The programs SPSS for Windows 25.0, SPSS Inc, Chicago, IL, USA and Microsoft Excel 11, Microsoft Corporation, Redmond, WA, USA were used for statistical analysis using nonparametric Mann-Whitney U test because the distribution of the data was not normal. The result was considered statistically significant if p<0.05.

RESULTS

Gestational age at delivery (G2 36.86 ± 3.79 vs. G1 38.94 ± 2.15; p=0.002) and birth weight (G2 2,841.36 ± 1,006.39 vs. G2 3,290.73 ± 745.6; p=0,032) were significantly different between the investigated groups. The difference between the peak systolic (p=0.002), peak diastolic blood pressure (p=0.007), TSH (p=0.044), and FT3 (p=0.045) were statistically significant. Impaired thyroid function was observed more often in G2 than in G1.

CONCLUSIONS

Thyroid function was more often affected adversely in pregnancies complicated with preeclampsia than with gestational hypertension. Based on the results of our study it might be prudent to check thyroid hormones in all asymptomatic pregnancies with preeclampsia or gestational hypertension. These findings need confirmation in larger better designed prospective studies.

The Association Between Hypertensive Disorders in Pregnancy and the Risk of Developing Chronic Hypertension

Objective

This meta-analysis comprehensively evaluated the association between hypertensive disorders in pregnancy (HDP) and the risk of developing chronic hypertension and the associations between specific types of HDP, including preeclampsia (PE) and gestational hypertension (GH), and the risk of developing chronic hypertension.

Design

Systematic review and meta-analysis.

Data Sources

The PubMed, Embase and Cochrane Library databases were searched from inception to August 20, 2021.

Methods

Depending on heterogeneity, the combined odds ratio (OR) of the 95% confidence interval (CI) was obtained with a random-effects or fixed-effects model. We used meta-regression analysis to explore the sources of heterogeneity. We analyzed the OR value after adjusting for age and BMI at recruitment, prepregnancy BMI, age at first delivery, and other factors. Additionally, we evaluated the results of the subgroup analysis by the year of publication (&lt; 2016, ≥ 2016), study design, sample size (&lt; 500, ≥ 500), region (North and South America, Europe, and other regions) and NOS score (&lt; 7, ≥ 7).

Results

Our systematic review and meta-analysis comprehensively explored the relationships between HDP, GH, and PE and chronic hypertension. Twenty-one articles that included 634,293 patients were included. The results of this systematic review and meta-analysis suggested that women with a history of HDP are almost 3.6 times more likely to develop chronic hypertension than those without a history of HDP, women with a history of GH are almost 6.2 times more likely to develop chronic hypertension than those without a history of GH, and women with a history of PE are almost 3.2 times more likely to develop chronic hypertension than those without a history of PE. In addition, we further calculated the probability of developing chronic hypertension among patients with HDP or PE after adjusting for age and BMI at recruitment, prepregnancy BMI, age at first delivery, and other factors. The results suggested that women with a history of HDP are almost 2.47 times more likely to develop chronic hypertension than those without a history of HDP and that women with a history of PE are almost 3.78 times more likely to develop chronic hypertension than those without a history of PE. People in Asian countries are more likely to develop chronic hypertension after HDP or PE, while American people are not at high relative risk.

Conclusion

These findings suggest that HDP, GH, and PE increase the likelihood of developing chronic hypertension. After adjustment for age and BMI at recruitment, prepregnancy BMI, age at first delivery, and other factors, patients with HDP or PE were still more likely to develop chronic hypertension. HDP may be a risk factor for chronic hypertension, independent of other risk factors. GH and PE, as types of HDP, may also be risk factors for chronic hypertension.

Systematic Review Registration

[www.ClinicalTrials.gov], identifier [CRD42021238599].