The Thyroid Hormone Axis and Female Reproduction

Possible association between subclinical hypothyroidism and age at menopause in Colombian women

OBJECTIVE

To evaluate the association between subclinical hypothyroidism with early menopause, premature menopause, and last menstrual bleeding before the natural age of menopause.

METHODS

This was a cross-sectional study conducted in 643 postmenopausal women aged 40-69 years. Groups were formed according to last menstrual episode: ≥45 [Natural age at menopause], 40-44 and [Early menopause], <40 [Premature menopause], and <45 [last menstrual episode before the natural age of menopause]. The Zulewski scale was applied to identify manifestations related to hypothyroidism and subclinical hypothyroidism, diagnosed with a serum TSH > 4.5 µIU/mL plus T4-free between 0.7 and 1.9 ng/dL.

RESULTS

It was found that 24.4% had the last menstrual episode before the natural age of menopause, 18.6% had early menopause, and 5.7% had premature menopause. Subclinical hypothyroidism was diagnosed in 4.5% of patients. Among women with subclinical hypothyroidism, there was a higher frequency of early menopause, premature menopause, and last menstrual episode before the natural age of menopause, than in women without subclinical hypothyroidism (p < 0.05). Paresthesia (50%) and dry skin (40.7%) were the most reported hypothyroidism-related manifestations. Early menopause, premature menopause, and last menstrual episode before the natural age of menopause were associated with subclinical hypothyroidism, OR: 3.37 [95% CI: 1.40-8.10], OR: 4.31 [95% CI: 1.24-14.97], and OR: 3.57 [95% CI: 1.57-8.10], respectively.

CONCLUSIONS

The last menstrual episode before the natural age of menopause, early menopause, and premature menopause were significantly associated with a higher chance of subclinical hypothyroidism.

Thyroid diseases and female sexual dysfunctions

INTRODUCTION

Female sexual dysfunctions (FSDs) have received little attention in the context of thyroid diseases, despite the high prevalence of both conditions.

OBJECTIVES

This review aims to update and summarize the state of knowledge on the association between thyroid diseases and FSDs and to investigate the complex mechanisms through which thyroid hormone imbalance can impact female sexual health in the context of the biopsychosocial model.

METHODS

A comprehensive literature search was performed through the PubMed, MEDLINE, and Scopus databases, using the following keywords: "female sexual function," "sexual dysfunction," "hypoactive sexual desire disorder," "thyroid disease," "thyroiditis," "hypothyroidism," and "hyperthyroidism."

RESULTS

To date, well-designed studies that describe the relationship between FSDs and thyroid disorders are lacking. However, despite the limitations on available studies, current data indicate that sexual alterations are frequently associated with thyroid diseases in women. A complex interplay of direct and indirect hormonal and nonhormonal mechanisms has been hypothesized, including hormonal changes, neurotransmitter imbalance, reduced nitric oxide release, mood disorders, and other systemic consequences of both hypothyroidism and hyperthyroidism. Thyroid hormone receptors have also been identified in the genitourinary system.

CONCLUSIONS

In a clinical setting, physicians should investigate the sexuality of patients consulting for thyroid disease. At the same time, an evaluation of thyroid function should be performed in patients presenting with FSD, especially after menopause, when the risk of thyroid diseases and FSDs increases strongly.

Autoimmune thyroid disease and ovarian hypofunction: a review of literature

Thyroid hormones(THs) are essential for the proper functioning of the ovaries, and multiple studies have shown that thyroid abnormalities, especially during adolescence and reproductive age, can lead to lifelong ovarian dysfunction. Autoimmune thyroid disease (AITD), one of the most common organ specific autoimmune diseases, is mainly mediated by cellular autoimmune reactions, and has strong inflammatory infiltration and immune active cells, including chemokines and cytokines, which are important components of ovarian aging. This suggests that autoimmune and inflammatory molecular processes may play a role in the emergence of ovarian dysfunction. The purpose of this review is to summarize recent in vivo and in vitro evidence of a complex relationship between AITD and ovarian dysfunction. AITD is closely related to the decline of ovarian function from the perspective of antibody, cytokine, oxidative stress, and genetic factors. Finally, some of the currently known treatments for AITD and hypo ovarian disease are summarized.

Menstrual Cycle Characteristics in Women With and Without Thyroid Disease

INTRODUCTION

This study was designed to evaluate the frequency and type of menstrual disorders in thyroid dysfunction. The relationship between thyroid dysfunction and menstrual disorders has been known for a long time. The menstrual cycle should be checked in women with thyroid dysfunction. On the contrary, women with menstrual irregularities should be investigated for thyroid dysfunction.

METHODS

Women who presented to our hospital's internal medicine and endocrinology clinics that recently diagnosed thyroid dysfunction were included. The patients were divided into five groups (subclinical hypothyroidism, overt hypothyroidism, subclinical hyperthyroidism, overt hyperthyroidism, and euthyroid) according to thyroid functions. They were questioned regarding the amount, frequency, and duration of menstrual bleeding. The prevalence of menstrual disturbances, including secondary amenorrhea, hypomenorrhea, oligomenorrhea, hypermenorrhea, polymenorrhea, menorrhagia, metrorrhagia, and menometrorrhagia, was examined in 485 patients and 108 healthy controls.

RESULTS

Hypermenorrhea was significantly more common in patients with overt hypothyroidism (33%) than in controls (6%) (p<0.05). The types and frequencies of menstrual disorders in patients with hyperthyroidism and those with normal thyroid function were not significantly different from those in controls.

CONCLUSION

Menstrual abnormalities frequently occur in women with thyroid dysfunction. Therefore, menstrual dysfunction should be considered when treating patients with thyroid abnormalities.

Hypothyroidism and Its Impact on Menstrual Irregularities in Reproductive-Age Women: A Comprehensive Analysis at a Tertiary Care Center

BACKGROUND

Hypothyroidism is known to affect a wide range of physiological systems, including menstrual function, in women of reproductive age. This study aims to comprehensively analyze the association between hypothyroidism and menstrual irregularities in women attending a tertiary care center.

METHODS

The study included 120 women aged 18-45 who presented with menstrual abnormalities. Convenience sampling was used to select participants from the outpatient department of obstetrics and gynecology. Thyroid function tests were conducted in the hospital's biochemistry laboratory, including assessments of thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), and thyroid peroxidase antibodies (TPOAb). The study aimed to determine the prevalence of hypothyroidism and its association with various menstrual irregularities, such as oligomenorrhea, polymenorrhea, menorrhagia, and amenorrhea. Data analysis was performed using SPSS software, applying descriptive statistics, Pearson correlation for continuous variables, and Chi-square tests for categorical variables. A significance level of p<0.05 was set for the analyses.

RESULTS

The mean age of the participants was 33.1 years (SD ± 7.2). The distribution of menstrual irregularities was 60 (50%) oligomenorrhea, 24 (20%) polymenorrhea, 24 (20%) menorrhagia, and 12 (10%) amenorrhea. Elevated TSH levels (>4.0 mIU/L) were observed in 42 (35%) of the participants, low FT4 levels (<0.8 ng/dL) in 18 (15%), low FT3 levels (<2.5 pg/mL) in 12 (10%), and elevated TPOAb levels (>55 IU/mL) in 24 (20%). A significant association was found between elevated TSH levels and oligomenorrhea (66 (55%), p<0.05) and between reduced FT4 levels and menorrhagia (78 (65%), p<0.05). Additionally, elevated TPOAb levels were significantly associated with amenorrhea (60 (50%), p<0.05). The correlation analysis showed a moderately positive correlation between TSH levels and the severity of menstrual irregularities (r=0.35, p<0.01). Subclinical hypothyroidism was detected in 25% of the participants, while 15% had clinical hypothyroidism.

CONCLUSION

This study underscores a notable link between hypothyroidism and menstrual irregularities in women of reproductive age. The results highlight the necessity of routine thyroid function screenings for women experiencing menstrual abnormalities, facilitating precise diagnosis and suitable treatment.

Urinary haloacetic acid concentrations and thyroid function among women: Results from the TREE study

BACKGROUND

Disinfection byproducts (DBPs) have been shown to impair thyroid function in experimental models. However, epidemiological evidence is scarce.

METHODS

This study included 1190 women undergoing assisted reproductive technology (ART) treatment from the Tongji Reproductive and Environmental (TREE) cohort from December 2018 to August 2021. Serum thyrotropin (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were measured as indicators of thyroid function. FT4/FT3 and TSH/FT4 ratios were calculated as markers of thyroid hormone homeostasis. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two most abundant HAAs, in urine were detected to assess individual DBP exposures.

RESULTS

After adjusting for relevant covariates, positive associations were observed between urinary TCAA concentrations and serum TSH and TSH/FT4 levels (e.g., percent change = 5.82 %, 95 % CI: 0.70 %, 11.21 % for TSH), whereas inverse associations were found for serum FT3 and FT4 (e.g., percent change = -1.29 %, 95 % CI: -2.49 %, -0.07 % for FT3). There also was a negative association between urinary DCAA concentration and serum FT4/FT3 (percent change = -2.49 %, 95 % CI: -4.71 %, -0.23 %). These associations were further confirmed in the restricted cubic spline and generalized additive models with linear or U-shaped dose-response relationships.

CONCLUSION

Urinary HAAs were associated with altered thyroid hormone homeostasis among women undergoing ART treatment.

Effects of crosstalk between steroid hormones mediated thyroid hormone in zebrafish exposed to 4-tert-octylphenol: Estrogenic and anti-androgenic effects

Alkylphenols, such as nonylphenol and 4-tert-octylphenol (OP), are byproducts of the biodegradation of alkylphenol ethoxylates and present substantial ecological and health risks in aquatic environments and higher life forms. In this context, our study aimed to explore the effect of OP on reproductive endocrine function in both female and male zebrafish. Over a period of 21 days, the zebrafish were subjected to varying concentrations of OP (0, 0.02, 0.1, and 0.5 μg/L), based on the lowest effective concentration (EC10 = 0.48 μg/L) identified for zebrafish embryos. OP exposure led to a pronounced increase in hepatic vitellogenin (vtg) mRNA expression and 17β-estradiol biosynthesis in both sexes. Conversely, OP exhibits anti-androgenic properties, significantly diminishes gonadal androgen receptor (ar) mRNA expression, and reduces endogenous androgen (testosterone and 11-ketotestosterone) levels in male zebrafish. Notably, cortisol and thyroid hormone (TH) levels demonstrated concentration-dependent elevations in zebrafish, influencing the regulation of gonadal steroid hormones (GSHs). These findings suggest that prolonged OP exposure may result in sustained reproductive dysfunction in adult zebrafish, which is largely attributable to the intricate reciprocal relationship between hormone levels and the associated gene expression. Our comprehensive biological response analysis of adult zebrafish offers vital insights into the reproductive toxicological effects of OP, thereby enriching future ecological studies on aquatic systems.

Mineral patterns in hair: A decisive factor between reproducible and repeat breeder dairy cows

Reproduction, especially impregnation, is a critical aspect of dairy cow management that directly influences herd milk productivity. We conducted a noninvasive hair mineral assay to compare the mineral profiles of two dairy cow groups: reproducible and repeat breeder, by investigating the levels of 11 essential minerals (Ca, Mg, Na, K, Fe, Cu, Mn, Zn, Cr, Se, and P) and 6 toxic elements (Hg, Pb, Cd, Al, As, and Ni) in both groups. We also conducted principal component and correlation matrix analyses to compare hair mineral patterns between the groups. Compared to their reproducible counterparts, repeat breeder cows had lower levels of Na, K, and Se. However, Fe, Cd, Al, and As levels were higher in repeat breeders than in their reproducible counterparts. The correlation matrix showed notable correlation patterns for each group. Ca, K, and Na levels were positively correlated in reproducible cows, whereas repeat breeder cows showed positive correlations only between Ca and K levels. Se showed positive correlations with Zn only in the reproducible cow group. Negative correlations were not found in the reproducible group, whereas the repeat breeder group exhibited 7 negative correlations. Despite the limitations of hair mineral analysis, this study provided useful insights into the reproductive potential of dairy cows. These findings aid in easing the prediction of repeat breeder occurrences in herds and are expected to facilitate timely mineral supplementation and other interventions to improve overall herd reproduction in dairy farms.

Impact of mildly evaluated thyroid-stimulating hormone levels on in vitro fertilization or intracytoplasmic sperm injection outcomes in women with the first fresh embryo transfer: a large study from China

PURPOSE

This study aimed to investigate the association between mild elevation of thyroid-stimulating hormone (TSH) levels and pregnancy outcomes of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatments in women with the first fresh embryo transfer.

METHODS

Large single-center retrospective cohort study of 15,728 patients from January 2018 to December 2022 were enrolled in the analyses. Clinical pregnancy rates, live birth rates, miscarriage rates, and ectopic pregnancy rates were compared between the TSH levels < 2.5 mIU/L group (N = 10,932) and TSH levels ≥ 2.5 mIU/L group (N = 4796). Subgroup analysis was performed for patients with TSH levels ≥ 2.5 mIU/L, dividing them into the thyroid peroxidase antibody (TPO)-negative group (N = 4524) and the TPO-positive group (N = 272).

RESULTS

There were no significant differences in the aforementioned pregnancy outcomes between the TSH levels < 2.5 mIU/L group and TSH levels ≥ 2.5 mIU/L group. Similarly, no significant differences were observed in the pregnancy outcomes between the TPO-negative group and the TPO-positive group.

CONCLUSION

Mildly elevated pre-conception TSH levels in thyroid-normal infertile patients did not have an impact on pregnancy outcomes of IVF/ICSI treatments.

Risk assessment of transgender people: implementation of a demasculinizing-feminizing rodent model including the evaluation of thyroid homeostasis

BACKGROUND

Individuals whose gender identity differs from the biological sex and the social norms are defined as transgender. Sometimes transgender undergo gender affirming hormone therapy, which lasts for the entire life making essential to evaluate its potential long-term effects. Moreover, transgender can represent a susceptible sub-group of population and specific attention is needed in risk assessment, including the development of targeted animal models. Aim of the study is the implementation of a rodent demasculinizing-feminizing model through the setting of appropriate dose of hormone therapy and the selection of specific biomarkers to evaluate the sex transition. Specific attention is paid to thyroid homeostasis due to the close link with reproductive functions. Four male adult rats/group were subcutaneously exposed to three doses plus control of β-estradiol valerate plus cyproterone acetate at: 0.045 + 0.2 (low), 0.09 + 0.2 (medium) and 0.18 + 0.2 (high) mg/dose, five times/week. The doses were selected considering the most recent recommendations for transgender woman. Sperm count, histopathological analysis (testis, liver, thyroid), testosterone, estradiol, triiodothyronine and thyroid-stimulating hormone serum levels and gene expression of sex dimorphic CYP450 were evaluated.

RESULTS

The doses induced feminizing-demasculinizing effects: decreased testosterone serum levels at the corresponding cisgender, increased estradiol, impairment of male reproductive function and reversal of sex-specific CYP liver expression. However, the medium and high doses induced marked liver toxicity and the low dose is considered the best choice, also for long-term studies in risk assessment. The alterations of thyroid indicated follicular cell hypertrophy supported by increased thyroid-stimulating hormone serum levels at the higher doses.

CONCLUSIONS

The implementation of animal models that mimic the effects of gender affirming hormone therapy is essential for supporting clinical studies in transgender people and filling data gap in order to ensure an appropriate risk assessment and a more accurate, personalized care for transgender people.

The causal association between thyroid disease and gout: A Mendelian randomization study

Observational studies have reported some associations between thyroid disease and gout, but the causal relationship between the 2 is not clear. We used Mendelian randomization (MR) Analysis to investigate the causal association between some thyroid diseases (autoimmune hypothyroidism, autoimmune hyperthyroidism, thyroid nodules, and thyroid cancer) and gout. GWAS data were used for analysis. The exposure factors were autoimmune hypothyroidism, autoimmune hyperthyroidism, thyroid nodules and thyroid cancer, and the outcome variables were gout. IVW, MR-Egger, Weighted median and Weighted mode were used for MR analysis. Cochran Q test MR-PRESSO and MR-Egger intercept analysis were used to detect heterogeneity and multi directivity. Autoimmune hypothyroidism has a causal effect on gout, IVW results show (OR = 1.13, 95% CI = 1.03-1.21, PFDR = 0.0336); Autoimmune hyperthyroidism has a causal effect on gout, IVW results show (OR = 1.07, 95% CI = 1.01-1.12, PFDR = 0.0314); Thyroid cancer has no causal effect on gout, IVW results show (OR = 1.03, 95% CI = 0.98-1.09, PFDR = 0.297); Thyroid nodules has no causal effect on gout, IVW results show (OR = 1.03, 95% CI = 0.98-1.08, PFDR = 0.225); Reverse MR Studies show that gout have no causal effect on the above thyroid diseases. Autoimmune hypothyroidism and autoimmune hyperthyroidism increase the risk of gout.