The prevalence of autoimmune thyroiditis is not increased in women with polycystic ovary syndrome after adjustment for family predisposition.

Purpose: Several studies suggest a linkage between PCOS and autoimmunity with a high frequency of chronic autoimmune thyroiditis (AIT) reported in PCOS patients, however, this subject remains controversial. The aim of this study was to investigate the prevalence of AIT in PCOS women and identify parameters that would serve as independent predictors of AIT.

Methods: Two hundred fifty seven (257) PCOS patients according to the NIH criteria and one hundred forty three (143) controls, women with normal menstrual cycles and without clinical or biochemical hyperandrogenism, were recruited for the study. Anthropometric characteristics and a complete family history for AIT were recorded. Thyroid hormones, antithyroid antibodies, androgen, glucose and insulin levels were measured. Thyroid gland structure was evaluated by ultrasound scan.

Results: Patients and controls did not differ in age, BMI as well as genetic predisposition for AIT (p > 0.05). Women with PCOS presented higher levels of androgens and HOMA-IR index, as expected. AIT prevalence did not differ between women with PCOS and controls (4.8 vs 9.3%, p = 0.13). However, the subgroup of PCOS patients with AIT presented a significantly stronger predisposition for AIT (33.3 vs 4.7%, p = 0.004) compared to patients without AIT. In a multivariate regression model, a positive family history of AIT was proved to be the strongest independent predictor of AIT in the PCOS group (OR 7.06, 95% CI 1.04-47.79, R = 0.39).

Conclusion: The prevalence of AIT in the PCOS patients does not differ from the general population when family predisposition to AIT is taken into account.