Effect of hypothyroidism and thyroid autoimmunity on the ovarian reserve: A systematic review and meta-analysis

Thyroid function tests and serum anti-Müllerian hormone in various populations, is there any association? A systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to evaluate the association between anti-Müllerian hormone (AMH) as a biomarker of ovarian reserve and various thyroid function tests, including thyroid-stimulating hormone (TSH), free T3 (FT3), free T4 (FT4), T3, T4, and thyroid autoantibodies, such as thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb), in various female populations.

METHODS

A comprehensive literature search was conducted across six electronic databases and original observational studies examining the correlation between AMH levels and at least one TFT, TPOAb, or TgAb.

RESULTS

Forty studies with 14,009 participants were included in the quantitative synthesis. The pooled results showed that AMH levels were not significantly correlated with TSH levels in the overall population or diverse subgroups. However, after adjusting for publication bias, a small, but significant, positive correlation was observed. Meta-regression analyses identified estradiol, FT3, and follicle-stimulating hormone (FSH) as significant moderators of AMH-TSH association in various populations. AMH was significantly positively correlated with FT3 (r = 0.177) and FT4 (r = 058), negatively correlated with T3 (r = - 0.202) and T4 (r = - 0.216) in the overall population, and significantly positively correlated with TPOAb in the normal population (r = 0.348). AMH levels were not significantly correlated with TgAb levels. Meta-regression revealed body mass index and FT4 as moderators in AMH-FT4 and AMH-TPOAb correlations.

CONCLUSION

These findings highlight the complex relationship between AMH and thyroid function markers with potential moderators influencing these associations. Further well-controlled longitudinal studies are required to clarify the underlying mechanisms and clinical implications of these associations across reproductive stages and metabolic profiles.

Ovarian function measures in normogonadotropic anovulation and subclinical thyroid dysfunction: a prospective cohort study

PURPOSE

To compare ovarian function measures in euthyroid women with normogonadotropic anovulation in subclinical hypothyroidism (SCH) or thyroid autoimmunity (TAI) to those without thyroid dysfunction.

DESIGN

A prospective open-label cohort study analyzed anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone, estradiol and testosterone concentrations, ovarian volume, and polycystic ovarian morphology (PCOM) incidence between women with and without SCH or TAI in two study arms: polycystic ovary syndrome (PCOS) and hypothalamic-pituitary-ovarian dysfunction (HPOD).

RESULTS

The prevalence of circulating thyroid peroxidase antibodies (TPOAb) was higher in the PCOS compared to the HPOD arm (p = 0.006). No significant differences in the measured parameters were observed based on SCH or TAI status across the entire cohort or individual study arms, except for phenotype D of PCOS, where a greater volume (p = 0.031) and higher incidence of physiological lesions (p = 0.047) in the left ovary were noted in SCH, and phenotype A, where LH concentrations (p = 0.038) were significantly higher in women without TAI. In the PCOS arm, thyroglobulin antibodies (TGAb) concentration correlated negatively with FSH (p = 0.049) and positively with testosterone (p = 0.012) concentrations, while in the HPOD arm, TPOAb and FSH concentrations were negatively correlated (p = 0.028).

CONCLUSIONS

No clinically significant impact of SCH on ovarian function measures was demonstrated. Regarding TAI, significant correlations with still uncertain clinical significance were observed with FSH concentrations, both in PCOS and in HPOD. In view of the obtained results, the benefits of thyroxine supplementation to address menstrual irregularities and improve obstetric outcomes in the examined conditions, require support with clinical evidence.

Subclinical/overt hypothyroidism may be associated with diminished ovarian reserve in infertile women independent of thyroid autoimmunity

Objective

To investigate the association between thyroid dysfunction or thyroid autoimmunity (TAI) and diminished ovarian reserve (DOR).

Methods

A total of 2,867 women undergoing their first in-vitro fertilization (IVF) cycle at Shenzhen Zhongshan Obstetrics & Gynecology Hospital between January 1, 2013 and June 30, 2021, were enrolled in this study. The participants had documented thyroid and ovarian reserve metrics. They were categorized into three groups based on their thyroid function: normal thyroid function (N = 2,540), subclinical/overt hypothyroidism (SCH/OH) (N = 290), and subclinical/overt hyperthyroidism (N = 37). Anti-Mullerian hormone (AMH) and antral follicle count (AFC) were assessed and collected. Women with AMH <1.2 ng/mL and AFC < 5 were diagnosed with DOR. Basic characteristics and ovarian reserve-related parameters were compared among the three groups. The association between thyroid function and ovarian reserve function was further analyzed using logistical regression analyses. In addition, the euthyroid population was stratified using a thyroid-stimulating hormone (TSH) threshold of 2.5 µIU/mL, and the ovarian reserve-related parameters were compared among women with low-normal TSH (TSH < 2.5 µIU/mL), high-normal TSH (2.5 µIU/mL ≤ TSH ≤ 4.2 µIU/mL) and SCH/OH.

Results

Women with SCH/OH had lower AMH levels (2.79 ng/mL vs. 3.41 ng/mL, P < 0.001) and a significantly higher prevalence of AMH level < 1.2ng/mL (17.2% vs. 12.1%, P = 0.015) compared to those with normal thyroid function. The prevalence of DOR was also higher among women with SCH/OH (10.0% vs. 6.5%, P = 0.036). There were no significant differences in ovarian reserve between women with normal thyroid function and those with subclinical/overt hyperthyroidism. Logistic regression analyses showed that the odds ratio (OR) of women with SCH/OH suffering from DOR was 1.666 (95% CI: 1.079-2.572) compared to those with normal thyroid function, after adjusting for TAI status and basic clinical characteristics. When the euthyroid group was stratified according to TSH levels, women with SCH/OH showed significantly lower AMH levels compared to women with low-normal TSH (2.79 ng/mL vs. 3.44 ng/mL, P < 0.001) and a significantly higher prevalence of DOR (10.0% vs. 6.0%, P = 0.010). Logistic regression analyses showed that the women with SCH/OH had an increased prevalence of DOR (OR: 1.819, 95% CI: 1.158-2.858) compared to those with low-normal TSH, after adjusting for TAI status and basic clinical characteristics. However, the OR for DOR among women with high-normal TSH was not significantly elevated compared to those with low-normal TSH (OR: 1.310, 95% CI: 0.936-1.832).

Conclusion

SCH/OH may be associated with DOR, irrespective of TAI status.

Primary ovarian insufficiency consequence of autoimmune diseases: a bidirectional two-sample Mendelian randomization study

Background

Observational studies suggest the risk of primary ovarian insufficiency (POI) is increased in autoimmune disorders (AIDs), but it is unclear whether there is a causal relationship. Therefore, we aimed to investigate the bidirectional causality between 20 AIDs and POI using Mendelian randomization (MR) analysis.

Methods

A bidirectional two-sample MR investigation was designed by using publicly accessible summary-level data from genome-wide association studies (GWAS). The inverse variance weighted (IVW) method was performed as the main analysis, supplemented by several sensitivity analyses. Cochran Q test was used to evaluate SNP estimate heterogeneity. MR-Egger and MR-PRESSO methods were utilized to detect horizontal pleiotropy.

Results

The MR analyses revealed that genetically determined coeliac disease (CeD) (OR = 1.124, 95% CI 1.033-1.224, P = 0.007), vitiligo (OR = 1.092, 95% CI 1.003-1.188; P = 0.042), systemic lupus erythematosus (SLE) (OR = 1.122, 95% CI 1.030-1.223, P = 0.008), and selective immunoglobulin A deficiency (SIgAD) (OR = 0.866, 95% CI: 0.776-0.967, P = 0.011) exhibited significant causal relationships with POI. We also found suggestive evidence of positive effect of Addison's disease (AD) towards POI (OR5e-6 = 1.076, 95% CI 1.002-1.154, P = 0.043).

Conclusion

This comprehensive MR analysis indicated that SLE, CeD, vitiligo, and AD caused an increased risk of POI, SIgAD was associated with a decreased risk of POI. These insights carry profound clinical implications, particularly emphasizing the early intervention for women with AIDs/POI who wish to preserve their reproductive potential or plan for future pregnancies.

Should we routinely assess ovarian reserve in girls and young women with autoimmune thyroid disease?

Background and aims

Some studies report that reproductive aged women with autoimmune thyroid disease (ATD) have a significantly higher risk of diminished ovarian reserve (OR). What is the best time to assessed OR in females with ATD? To answer this question, we assessed OR in girls and young women with ATD and reviewed the current literature regarding on the topic.

Methods

The study included 70 patients with ATD, mean 14.4 ± 3.3 years, and 29 age-matched controls. Follicle-stimulating hormone (FSH), luteinizing hormone, estradiol, prolactin, thyroid stimulating hormone, free thyroxin, thyroid peroxidase antibody, thyroglobulin antibody and Anti-Mullerian Hormone (AMH), and Inhibin-B were measured in all participants, if possibly on day 3-5 of the menstrual cycle.

Results

Most ATD patients were euthyroid. All participants have normal OR. We found a significantly positive correlation between AMH and Inhibin-B in ATD patients and between Inhibin-B and FSH in both groups.

Conclusions

The results of our study and the literature review indicate that euthyroid adolescents with ATD do not have impaired OR. Routine evaluation of OR in adolescents with ATD does not seem necessary. But OR should be assessed in everyone with ATD and hypothyroidism, because not the presence of ATD but euthyroidism matters to OR.

Excess of severe autoimmune diseases in women with premature ovarian insufficiency: a population-based study

STUDY QUESTION

Is there an association between premature ovarian insufficiency (POI) and severe autoimmune diseases before and after POI diagnosis?

SUMMARY ANSWER

Women with POI had at least one hospital-treated autoimmune disorder preceding POI diagnosis 2.6 times more often compared with matched female controls, and a 2- to 3-fold risk for these diseases for several years after POI diagnosis.

WHAT IS KNOWN ALREADY

It has been suggested that autoimmunity is an important factor in the pathogenesis of POI. Estimations of the prevalence of POI cases with autoimmune origin have ranged from 4% to 50%.

STUDY DESIGN, SIZE, DURATION

This population-based registry study included 3972 women diagnosed with spontaneous POI between 1988 and 2017 and 15 708 female population controls and used both case-control and cohort analysis. Autoimmune disease diagnoses were evaluated from childhood until the end of the year 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women with POI were identified from the reimbursement registry of the Finnish Social Insurance Institution by their right to hormone replacement therapy (HRT). Four female population controls matched by age and municipality of residence were searched for each POI case to form a reference cohort. Women with a history of cancer or bilateral oophorectomy were excluded. Severe autoimmune disorder diagnoses for the years 1970-2017 were identified from the Hospital Discharge Registry. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated using binary logistic regression for cases of having any, or one or more, specific autoimmune diseases preceding the index date (the date when reimbursement for HRT was granted for the POI) among women with POI as compared to controls. Standardized incidence ratios (SIR) with 95% CIs for getting diagnosed with an autoimmune disease after the index date in 3-year follow-up periods among women with POI (who did not have these diseases prior to the index date) were also calculated. The expected numbers of autoimmune disease cases were based on the incidence of first-onset severe autoimmune disease among the controls.

MAIN RESULTS AND THE ROLE OF CHANCE

The prevalence of having at least one severe autoimmune disease in women with POI was 5.6% (n = 233), with an OR of 2.6 (95% CI 2.2, 3.1) when compared to population controls. Women with POI had an increased prevalence of several specific autoimmune diseases prior to the index date compared to controls: polyglandular autoimmune diseases (OR 25.8, 95% CI 9.0, 74.1), Addison's disease (OR 22.9, 95% CI 7.9, 66.1), vasculitis (OR 10.2, 95% 4.3, 24.5), systemic lupus erythematosus (OR 6.3 95% CI 4.2, 20.3), rheumatoid arthritis (OR 2.3, 95% CI 1.7, 3.2), sarcoidosis (OR 2.3, 95% CI 1.2, 4.5), inflammatory bowel diseases (OR 2.2, 95% CI 1.5, 3.3), and hyperthyroidism (OR 1.9, 95% CI 1.2, 3.1); whereas the prevalence of diabetes type 1 and ankylosing spondylitis did not differ between the women with POI and the reference cohort. The SIRs for being diagnosed for the first time with a severe autoimmune disease after POI diagnosis was 2.8 (95% CI 2.3, 3.4), during the first three years after POI diagnosis, decreasing gradually to 1.3 (1.1, 1.6) after 12 years.

LIMITATIONS, REASONS FOR CAUTION

This study only included autoimmune disorders diagnosed in specialized health care; hence, the overall prevalence of autoimmune disorders in women with POI may be higher.

WIDER IMPLICATIONS OF THE FINDINGS

Severe autoimmune diseases have a strong association with POI, suggesting that immunological mechanisms play a pivotal role in POI. Future studies should focus on specific autoimmune mechanisms behind POI, from both preventive and curative perspectives.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by Oulu University Hospital. S.M.S. received grants from the Finnish Menopause Society, the Finnish Medical Foundation, and the Juho Vainio Foundation. H.S. received grants from the Finnish Menopause Society, the Oulu Medical Research Foundation, the Finnish Research Foundation of Gynecology and Obstetrics, UniOGS graduate school, The Finnish Medical Society Duodecim, Orion Research Foundation, and the University of Oulu Scholarship Fund. M.-M.O. received a grant from the Sakari Alhopuro Foundation and the Finnish Diabetes Research Foundation. None of the funders had any involvement in the study design or its execution or reporting. The authors do not have any competing interests to report.

TRIAL REGISTRATION NUMBER

N/A.

Assessment of Thyroid Auto-antibodies in Euthyroid Infertile Women with Polycystic Ovarian Syndrome - A Cross-sectional Analytical Study

Background

Thyroid auto-antibodies could be one of the many causes of infertility in women, especially with polycystic ovarian syndrome (PCOS) with a prevalence of 5%-15%. Patients with anti-thyroid antibodies have shown significantly lower fertilisation rates, implantation rates, lower pregnancy rates and increased risk of first-trimester abortions when compared with those without anti-thyroid antibodies.

Aim

The aim of the study was to assess the prevalence of thyroid auto-antibodies in euthyroid infertile women with PCOS and to compare the prevalence of thyroid autoantibodies in euthyroid infertile women with PCOS and without PCOS.

Settings and Design

This is a cross sectional analytical study involving 132 Infertile women with and without PCOS visiting the department of OBG in a tertiary care center. The study was conducted for period of 2 years.

Materials and Methods

A total of one hundred two women were enrolled in to the study. Sixty six women (66) had features of PCOS based on Rotterdam's criteria and 66 women were controls without PCOS features. Detailed history and examination were done for all women after taking informed and written consent. Previous hospital records were collected along with all biochemical investigations. The blood sample was collected for hormonal levels and thyroid auto-antibodies (anti-thyroid peroxidase [TPO] and anti-thyroglobulin [TG]) were assessed by enzyme-linked immunosorbent assay. The antibody levels were compared between the two groups along with the other parameters.

Statistical Analysis Used

Statistical tests were done using SPSS version 26. The Chi-square test or Fisher's exact test would be used to study the association of categorical data like the presence of hirsutism, acne, etc. The association of independent variables with outcome variables was assessed using Chi-square. The P < 0.05 was considered significant with a confidence interval of 95%.

Results

Anti-TPO antibody levels were found to be elevated in 25.4% of the PCOS group in comparison to only 3% of the non-PCOS group. Anti-TG antibodies of >100 U/mL were seen in 23 patients (34.3%) in PCOS group in comparison to two patients (3%) in non-PCOS group (P = 0.001). Both the antibodies (anti-TPO and anti-TG) were present in 21.2% of the PCOS group and 1.5% of the non-PCOS group.

Conclusion

Women with PCOS were found to be 11 times more likely to have anti-TPO antibodies and 20 times more likely to have anti-TG antibodies compared to non-PCOS women. This heightened prevalence of anti-thyroid antibodies suggests that testing for these antibodies may be warranted in women with PCOS, even if they have normal thyroid function. However, further studies with larger sample sizes are needed to validate these findings.

A Review of Autoimmune Thyroid Diseases and Their Complex Interplay with Female Fertility

Hashimoto thyroiditis and Graves' disease are autoimmune thyroid disorders that are common in women of reproductive age and have a complex relationship with female fertility and health of the maternal-fetal dyad. Both hyperthyroidism and hypothyroidism, whether subclinical or overt in severity, directly or indirectly affect nearly every level of the hypothalamic-pituitary-ovary axis, uterine and ovarian function, as well as fetal development from implantation through delivery. Autoimmunity itself also appears to negatively impact both spontaneous and assisted fertility, as well as miscarriage risk, although the mechanism remains unclear, and the presence and magnitude of risk is variable in published literature. While treatment of overt hyperthyroidism and hypothyroidism is unequivocally recommended by professional societies, the impact of treatment on fertility outcomes, and the role of treatment in subclinical thyroid disease is more controversial. Unfortunately, levothyroxine has not been shown to abrogate the risk of subfertility and miscarriage observed in euthyroid thyroid autoantibody positive women.

Metabolic Risk in Patients with a Diminished Ovarian Reserve and Premature Ovarian Insufficiency

Objective: Diminished ovarian reserve (DOR) and premature ovarian insufficiency (POI) represent conditions of different severity, characterized by an earlier-than-expected decrease in ovarian activity. The present study aims to compare metabolic disturbances between women with DOR and patients with POI from a different origin. Materials and methods: A total of 226 women (28 healthy women; 77 individuals with DOR, and 121 patients with POI/36 with Turner syndrome [TS] and 85 with non-TS POI/) have been studied retrospectively. Data concerning anthropometric indices, and metabolic parameters were collected. Results: Patients with DOR, non-TS POI, and TS had increased blood pressure and liver enzymes, pronounced insulin resistance, and worse lipid profiles than controls (p < 0.008 for all). TS patients had significantly higher ASAT, GGT, and TSH levels compared to non-TS POI and DOR individuals. The prevalence of type 2 diabetes tended to be higher in TS women compared to other groups. The prevalence of previously diagnosed polycystic ovarian syndrome was lower in the non-TS POI patients than in the DOR patients (p = 0.005). Conclusions: patients with decreased ovarian function suffer from insulin resistance, abnormal lipid profile, and subtle hepatic disturbances, irrespective of the severity of the condition and the presence of chromosomal aberrations.

Anti-Müllerian Hormone Level Determinants among Non-Polycystic-Ovary-Syndrome Women Undergoing In Vitro Fertilization: A Retrospective Cross-Sectional Study

Background and Objectives: The anti-Müllerian hormone (AMH) is a crucial biomarker in regulating ovarian follicle development and female fertility. AMH levels predict ovarian responses in in vitro fertilization (IVF) cycles, helping clinicians tailor treatment strategies. This study aims to determine whether thyroid autoimmunity, age, body mass index (BMI), sexual hormone levels, and 25-hydroxyvitamin D levels influence serum AMH in non-polycystic-ovary-syndrome (PCOS) euthyroid women. Materials and Methods: This retrospective cross-sectional study examined 52 female patients at Zygota Fertility Clinic between 2018 and 2022. Women aged 20-45 years with regular menstrual cycles were included, while conditions such as abnormal thyroid-stimulating hormone (TSH) levels, PCOS, and systemic autoimmune diseases were excluded. A number of parameters were measured in the study, including the subjects' age, BMI, 25-hydroxyvitamin D, serum free thyroxine (fT4), TSH, various antibodies, and a range of reproductive hormones. An analysis of the relationships between AMH and other variables was conducted using Spearman's correlation coefficient, and an assessment of the impact of confounding factors on AMH levels was conducted using a multivariable linear regression model. Results: The results revealed significant negative correlations between AMH levels and age (rho: -0.484, p < 0.001) and follicle-stimulating hormone (FSH) (rho: -0.550, p < 0.001), while positive correlations existed between AMH and estradiol (rho: 0.352, p = 0.011) and total testosterone (rho: 0.542, p < 0.001). No significant correlations were found between AMH levels and BMI, LH, or 25-hydroxyvitamin D. Conclusions: In this study, ovarian reserve was influenced by age, estradiol, and total testosterone in non-PCOS euthyroid women undergoing IVF. Conversely, BMI and vitamin D status did not significantly impact AMH levels. In order to better understand and possibly manage ovarian reserve, a holistic approach is absolutely essential, taking into account age, weight, hormonal balance, nutrition, and thyroid health.

Evaluation of ovarian reserve in women with thyroid autoimmunity

OBJECTIVE

To compare the ovarian reserve of women of reproductive age with and without thyroid autoimmunity (TAI).

METHODS

We performed a retrospective analysis of medical records from an assisted reproduction clinic from February 2017 to December 2021. Women aged between18 and 47 years with data on antithyroperoxidase and antithyroglobulin (anti-Tg) antibodies and assessment of ovarian reserve by anti-müllerian hormone (AMH) and antral follicle count (AFC) were included. Among the 188 participants included, 63 were diagnosed with TAI, and 125 had both antibodies negative. AMH and AFC were compared between groups. Subanalysis based on age, types of antibodies, and thyroid function markers were performed. In addition, bivariate analysis and regression models were used.

RESULTS

Overall, there was no difference in the median levels of AMH or AFC between the two groups. However, in the subgroup analysis by age, we observed a trend towards lower median levels of AMH in women over 39 years with TAI (0.9 ng/mL vs. 1.5 ng/mL, p=0.08). In a subanalysis according to antibodies, we found a significantly lower median AFC in the group with anti-Tg than in the group without this antibody (8.0 follicles vs. 11.5 follicles, p=0.036). We also found a significantly higher prevalence of anti-Tg in patients with low ovarian reserve compared to those with normal reserve (60.7% vs. 39.3%, p=0.038).

CONCLUSIONS

The ovarian reserve of women with TAI appears to be insidiously compromised over the years, with a decreased ovarian reserve in women with anti-Tg.

Protective effect of thyroid and restores of ovarian function of Buzhong Yiqi granule on experimental autoimmune thyroiditis in female rats

OBJECTIVE

To observe the effects of Buzhong Yiqi granule on thyroid function and ovarian function in rats with experimental autoimmune thyroiditis (EAT).

METHODS

EAT model was replicate by using the method of mixing and injecting porcine thyroglobulin with Freund's adjuvant and high iodine. Rats were randomly divided into normal control (NC) group, EAT model (EAT) group, selenium yeast (PC) group, low dose Buzhong Yiqi (BZYQ-L) group, medium dose Buzhong Yiqi (BZYQ-M) group and high dose Buzhong Yiqi (BZYQ-H) group. After two months of drug intervention according to dosage, enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), anti-thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) in peripheral blood of rats. The pathological changes of rat thyroid tissues were observed under light microscope with HE staining; ELISA was used to determine estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), anti-müllerian hormone (AMH), and the pathological changes of rat ovarian tissues were observed under light microscope with hematoxylin and eosin staining.

RESULTS

Compared with the NC group, BZYQ granule improved the thyroid and ovarian tissue morphology, and the levels of TPOAb, TGAb and TSH in the model group rats significantly increased (P < 0.05), the thyroid tissue was severely destroyed, the levels of E2, FSH, LH, T, AMH significantly increased (P < 0.05), and the ovary exhibited polycystic changes; Compared with the model group, TSH level in the BZYQ-L group rats decreased (P < 0.05), FSH, T, AMH levels decreased (P < 0.05), in the BZYQ-M group TPOAb, TSH levels decreased (P < 0.05), FSH, LH, T, AMH levels significantly decreased (P < 0.05), BZYQ-H group TPOAb, TGAb, TSH levels significantly decreased (P < 0.05), FSH, LH, T, AMH levels significantly decreased (P < 0.05), with the greatest improvement and significantly better than selenium yeast group (P < 0.05).

CONCLUSIONS

BZYQ granule could regulate the thyroid function of EAT rats, reduce thyroid antibody titers, then act on the ovarian function, regulate hormone disorders, and alleviate the pathological damage of rat's ovarian tissues. The effect of high dose Buzhong Yiqi granule is the best.

Anti-Müllerian hormone beyond an ovarian reserve marker: the relationship with the physiology and pathology in the life-long follicle development

Anti-Müllerian hormone (AMH), an indirect indicator of the number of remaining follicles, is clinically used as a test for ovarian reserve. Typically, a decline suggests a decrease in the number of remaining follicles in relation to ovarian toxicity caused by interventions, which may implicate fertility. In contrast, serum AMH levels are elevated in patients with polycystic ovary syndrome. AMH is produced primarily in the granulosa cells of the preantral and small antral follicles. Thus it varies in association with folliculogenesis and the establishment and shrinking of the follicle cohort. Ovarian activity during the female half-life, from the embryonic period to menopause, is based on folliculogenesis and maintenance of the follicle cohort, which is influenced by developmental processes, life events, and interventions. AMH trends over a woman's lifetime are associated with in vivo follicular cohort transitions that cannot be observed directly.

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.

Polycystic ovary syndrome and thyroid disorder: a comprehensive narrative review of the literature

Background

Published data on the relationship between polycystic ovary syndrome (PCOS) and thyroid dysfunction are sparse and confusing.

Objective

To comprehensively review data available in the literature regarding the relationship between PCOS and the thyroid function, and its abnormalities.

Methods

Nine main areas of interest were identified and analyzed according to the available evidence: 1) Evaluation of thyroid function for PCOS diagnosis; 2) Epidemiology data on thyroid function/disorders in patients with PCOS, and vice versa; 3) Experimental data supporting the relationship between thyroid function/disorders and PCOS; 4) Effects of thyroid function/disorders on PCOS features, and vice versa; 5) Effect of thyroid alterations on the cardiometabolic risk in women with PCOS; 6) Effect of thyroid abnormalities on reproductive outcomes in women with PCOS; 7) Relationship between thyroid function/abnormalities in patients with PCOS who are undergoing fertility treatment; 8) Effect of treatments for thyroid diseases on PCOS; and 9) Effect of treatments for PCOS on thyroid function. An extensive literature search for specific keywords was performed for articles published from 1970 to March 2023 using PubMed and Web of Science. Data were reported in a narrative fashion.

Results

PCOS is a diagnosis of exclusion for which diagnosis is possible only after excluding disorders that mimic the PCOS phenotype, including thyroid dysfunctions. However, the tests and the cutoff values used for this are not specified. Many experimental and clinical data suggest a relationship between perturbations of the thyroid function and PCOS. Direct and unequivocal evidence on the effects of thyroid function/disorders on PCOS features are lacking. High thyroid-stimulating hormone levels and subclinical hypothyroidism may be associated with significant worsening of several intermediate endpoints of cardiometabolic risk in women with PCOS. Thyroid abnormalities may worsen reproductive outcomes, especially in patients undergoing fertility treatment. To date, there are no data demonstrating the efficacy of thyroid medications on fertility and cardiometabolic risk in women with PCOS. Lifestyle modification changes, metformin, and vitamin D seem to improve thyroid function in the general population.

Conclusion

PCOS and thyroid disorders are closely related, and their coexistence may identify patients with a higher reproductive and metabolic risk. Regular screening for thyroid function and thyroid-specific autoantibodies in women with PCOS, particularly before and during pregnancy, is highly recommended.

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.

A Cross-Species Analysis Reveals Dysthyroidism of the Ovaries as a Common Trait of Premature Ovarian Aging

Although the imbalance of circulating levels of Thyroid Hormones (THs) affects female fertility in vertebrates, its involvement in the promotion of Premature Ovarian Aging (POA) is debated. Therefore, altered synthesis of THs in both thyroid and ovary can be a trait of POA. We investigated the relationship between abnormal TH signaling, dysthyroidism, and POA in evolutionary distant vertebrates: from zebrafish to humans. Ovarian T3 signaling/metabolism was evaluated by measuring T3 levels, T3 responsive transcript, and protein levels along with transcripts governing T3 availability (deiodinases) and signaling (TH receptors) in distinct models of POA depending on genetic background and environmental exposures (e.g., diets, pesticides). Expression levels of well-known (Amh, Gdf9, and Inhibins) and novel (miR143/145 and Gas5) biomarkers of POA were assessed. Ovarian dysthyroidism was slightly influenced by genetics since very few differences were found between C57BL/6J and FVB/NJ females. However, diets exacerbated it in a strain-dependent manner. Similar findings were observed in zebrafish and mouse models of POA induced by developmental and long-life exposure to low-dose chlorpyrifos (CPF). Lastly, the T3 decrease in follicular fluids from women affected by diminished ovarian reserve, as well as of the transcripts modulating T3 signaling/availability in the cumulus cells, confirmed ovarian dysthyroidism as a common and evolutionary conserved trait of POA.

Impact of Thyroid Autoimmunity on Assisted Reproductive Technology Outcomes and Ovarian Reserve Markers: An Updated Systematic Review and Meta-Analysis

Background: Thyroid autoimmunity (TAI) has a high prevalence among women of reproductive age. Investigating its possible impact on ovarian function and fertility is, thus, of utmost relevance. The aim of this systematic review and meta-analysis was to elucidate the effect of TAI on both assisted reproductive technology (ART) outcomes and ovarian reserve. Methods: This systematic review and meta-analysis was restricted to two groups of research articles investigating the association between TAI and: (1) autologous ART outcomes (i.e., fertilization rate [FR], implantation rate, clinical pregnancy rate [CPR], miscarriage rate, and live birth rate), (2) markers of ovarian reserve (i.e., anti-Müllerian hormone, basal follicle stimulating hormone, antral follicle count, and number of oocytes retrieved). Studies including women affected by overt hypo/hyperthyroidism were excluded. Relevant studies were identified by a systematic search in PubMed, MEDLINE, ClinicalTrials.gov, Embase, and Scopus, from database inception to May 1, 2022. Results: From a total of 432 identified publications, 22 studies were included in Group 1 and 26 studies in Group 2. The presence of TAI was associated with a higher risk of miscarriage (7606 participants, odds ratio [OR] 1.52, confidence interval [CI 1.14-2.01], p = 0.004, I² = 53%), lower chance of embryo implantation (7118 participants, OR 0.72, [CI 0.59-0.88], p = 0.001, I² = 36%), and live birth (11417 participants, OR 0.73, [CI 0.56-0.94], p = 0.02, I² = 71%). These associations were no longer observed in a subgroup analysis of patients who exclusively underwent intracytoplasmic sperm injection (ICSI). The FR and CPR as well as the mean values of surrogate markers of oocyte quantity appeared not to be affected by TAI. Conclusions: This data synthesis suggest a higher risk of adverse ART outcomes in women with positive TAI. However, the reliability of these findings is hampered by the relatively low quality of the evidence and significant heterogeneity in many of the meta-analyses. The possible protective effect of ICSI is promising but should be confirmed in controlled prospective clinical trials. PROSPERO Registration ID: CRD42021236529.

Evaluation of anti-Müllerian hormone in pre-menopausal women stratified according to thyroid function, autoimmunity and age

Background

AMH is a reliable index of ovarian reserve. It is not clear whether, or how much, thyroid function and/or thyroid autoimmunity can impair ovarian function and AMH secretion in the long term.

Aim

This retrospective cross-sectional study compared AMH levels in pre-menopausal women with/without positive thyroid autoimmunity or hypofunction.

Methods

From January 2019 to May 2022, AMH was evaluated in 250 pre-menopausal women not undergoing assisted fertility procedures who were referred to a secondary endocrine centre. Thyroid function and autoimmunity, sonographically measured thyroid volume, FSH and E2 in the early follicular phase, and PRL and progesterone in the luteal phase were also evaluated. Exclusion criteria were: age < 18 years, genetic hypogonadism, pregnancy and previous treatments that have potentially damaging effects on gonads.

Results

We evaluated 171 women (mean age ± SD: 31.5 ± 9.0 years) off L-T4 treatment and 79 women on L-T4 treatment (39.7 ± 9.5 years; P < 0.001). AMH (median, IQR, CI) was 16.1 pmol/l (7.1 – 35.7 pmol/l, 21.4 – 29.9 pmol/l) and 7.6 pmol/l (1.4 – 17.8 pmol/l, 8.6 – 14.7 pmol/l; P < 0.001), respectively. When the women were stratified according to age (18-25, 26-30, 31-35, 36-40, 41-45, > 46 years) no significant difference emerged between those on/off L-T4 treatment in groups of the same age-range. In women on- or off-L-T4 treatment, AMH was negatively related with age on univariate and multivariate analyses (P < 0.0001). In both groups, AMH was negatively related to FSH (P < 0.0001). On multivariate analysis, AMH was positively related to the age of the mother on spontaneous menopause (P = 0.006) and negatively to thyroid volume (P = 0.02) in women on L-T4. AMH levels were significantly (P = 0.03) higher in TPOAb-negative than in TPOAb-positive women, but age was significantly (P = 0.001) lower in TPOAb-negative than in TPOAb-positive women.

Conclusions

In our cohort of women, age proved to be a better predictor of AMH levels than any of the other factors linked to thyroid function and autoimmunity. Our data do not support the hypothesis that subclinical hypothyroidism and/or autoimmunity are associated with decreased ovarian reserve. However, a larger number of cases is needed in order to obtain conclusive data.