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.