Thyroid Function Abnormalities in Women With Polycystic Ovary Syndrome

Abstract

Polycystic ovary syndrome (PCOS) is among the commonest endocrine conditions of women of reproductive age, and thyroid disease is among the commonest endocrine conditions of women in general. It is hardly surprising that the two are often found together, but whether they are linked by more than chance is less clear. This narrative review asks what the published literature says about thyroid function abnormalities in women with PCOS, how those abnormalities are defined and measured, and how much weight the evidence can bear. It draws on work on the diagnosis of PCOS, thyroid physiology and autoimmunity, insulin resistance and adiposity, and reproductive and pregnancy outcomes, and it reports no new data. Several studies describe more frequent subclinical hypothyroidism and thyroid autoimmunity in women with PCOS, but the reports differ in diagnostic criteria, reference ranges, body weight, iodine status and the populations sampled, and many are small, single-centre and cross-sectional. Two broad explanations are discussed: a shared autoimmune or hormonal background, and a metabolic route through insulin resistance and adiposity. Neither has been shown to be sufficient. The review concludes that thyroid testing in PCOS is reasonable, that a single raised thyrotropin result should be interpreted with care, and that larger, prospective studies using consistent criteria are needed.