Functional ovarian reserve in women with infertility and euthyroidism: what is the role of thyroid autoimmunity?

Abstract

Background: Thyroid dysfunction is the most common endocrine disorder in women of childbearing age, and is associated with menstrual irregularities, anovulation and infertility. Whether it is thyroid function, thyroid autoimmunity (AI) or both that affects functional ovarian reserve remains to be clarified. The aim of this study was to evaluate the association between functional ovarian reserve and thyroid AI in women with infertility in euthyroidism. Methods: retrospective study of women with infertility, in euthyroidism, followed in a Human Reproduction Department, between May 2016 and January 2020. TSH, anti-thyroid peroxidase (TPO) antibodies, anti-thyroglobulin (TG) antibodies were measured. Functional ovarian reserve was assessed by anti-Müllerian hormone (AMH) levels with antral follicle count (AFC) performed by endovaginal ultrasound. Women with at least one of the following criteria were excluded: prior thyroidectomy, radioactive iodine treatment, cervical surgery/radiotherapy, oophorectomy, malignant/autoimmune pathology, chronic kidney disease, liver disease, polycystic ovary syndrome, current pregnancy and current medication with levothyroxine, methimazole or propylthiouracil. Results with p<0.05 were considered statistically significant. Results: 730 women were evaluated, with mean age of 34.9±3.9 years, with positive thyroid AI (≥ 1 positive antibody) present in 14.8% of cases. Anti-TPO antibodies were positive in 11.0% of patients and anti-TG antibodies in 7.0%. Mean TSH level was 1.6±0.7 µIU/mL (NR: 0.4-4.0). Median body mass index (BMI) was 22.8 kg/m2 (IQR 5.1). Median AMH was 1.7ng/mL (IQR 2.1), and mean AFC was 10.2±6.3. Patients with positive and negative thyroid AI did not differ significantly with age (p=0.133), BMI (p=0.784], AFC (p=0.508) and AMH (p=0.825). TSH levels were significantly higher in the positive AI group (2.0±0.8 vs 1.5±0.7µIU/mL; p<0.001). In the univariate and multivariate analysis, only patient's age and AFC were predictive of AMH levels (p<0.001; p<0.001, respectively). TSH levels, BMI and thyroid AI were not predictive of AMH levels. In regard to AFC, in the univariate analysis, only age was predictive (p<0.001). TSH levels, BMI and thyroid AI were not predictive of AFC. Conclusions: In this study we found that thyroid autoimmunity, in women with infertility and TSH levels in the normal range, apparently, do not have a predictive role for functional ovarian reserve.