Background: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in reproductive age women, yet its clinical presentation shares similarities with several other endocrine disorders such as thyroid disease. Hence, the objective of this study was to further evaluate this association by investigating the clinical, hormonal, and metabolic parameters between subclinical hypothyroidism (SCH) and PCOS.

Methods: This is a cross-sectional study conducted in a tertiary care clinic at Cleveland, Ohio, USA. A total of 137 women diagnosed with PCOS by Rotterdam criteria were examined. SCH was defined as thyroid-stimulating hormone >2.5 mIU/L in the absence of symptoms of overt hypothyroidism. The mean age, body mass index (BMI), fasting plasma glucose (FPG), glucose tolerance test, hemoglobin A1c, fasting insulin, a 2 hours insulin level after 75 g glucose load, cholesterol, LDL, HDL, and homeostatic model assessment (HOMA) were compared between women with and without SCH. Logistic regression was used to adjust for age and BMI.

Results: Among 137 women with PCOS, 21.9% had SCH. Comparison groups were similar in both age and BMI and there was no difference in the mean values of all endocrine and metabolic parameters tested. However, abnormal FPG levels (OR 3.01; CI: 1.12–8.07. p = 0.03) and abnormal HOMA (OR 3.7; CI: 1.14–12.00. p = 0.03) were more likely in women who had SCH than in women without SCH independent of age and BMI.

Conclusions: Women with PCOS and SCH are more likely to have impaired FPG values and impaired insulin sensitivity even after adjusting for age and BMI. Hence, close monitoring of PCOS patients for SCH may be beneficial.