Aim: To investigate risk of thyroid disease in Danish women with PCOS.
Design: National register-based study on women with PCOS in Denmark. 18,476 women had a diagnosis of PCOS in the Danish National Patient Register. PCOS Odense University Hospital (PCOS OUH, N=1,146) was an embedded cohort of women with PCOS and clinical and biochemical examination. Three age-matched controls were included for each woman with PCOS (N=54,757). The main outcome measures were thyroid disease (hypothyroidism, Graves’ disease, goitre, thyroiditis) according to diagnosis codes and/or inferred from filled medicine prescriptions. Associations between baseline TSH and development of cardio-metabolic disease was examined in PCOS OUH.
Results: The median (quartiles) age at inclusion was 29 (23-35) years and follow up duration was 11.1 (6.9–16.0) years. The Hazard ratio (95% CI) for thyroid disease development was 2.5 (2.3; 2.7) (p<0.001). The event rate of thyroid disease was 6.0 per 1000 patient years in PCOS Denmark versus 2.4 per 1000 patient years in controls (p<0.001). Women in PCOS OUH with TSH ≥2.5 mIU/L (n=133) had higher BMI (median 29 vs. 27 kg/m2), wider waist, higher triglycerides and free testosterone by the time of PCOS diagnosis compared to women in PCOS OUH with TSH <2.5 mIU/L (n=588). Baseline TSH did not predict later development of cardio-metabolic diseases in PCOS OUH.
Conclusions: The event rate of thyroid disease was significantly and substantially higher in women with PCOS compared to controls.