Low 25 (OH) vitamin D levels are associated with autoimmune thyroid disease in polycystic ovary syndrome

Low 25(OH) vitamin D levels have been associated with several autoimmune diseases and recently with autoimmune thyroid disease (AITD). The aim of the study was to investigate the association of AITD with 25(OH) vitamin D levels in women with polycystic ovary syndrome (PCOS). Fifty women with PCOS were consecutively enrolled and underwent routine health checkups, which included measurements of 25(OH) vitamin D, anti-thyroid peroxidase (TPO-Ab), anti-thyreoglobulin (TG-Ab) antibodies, FT3, FT4, and TSH. Selecting 50 nmol/L as cut-off point, low 25(OH) vitamin D levels were detected in 23 of 50 patients (46 %). AITD was diagnosed when TPO-Ab levels exceeding 80 U/ml and/or TG-Ab levels exceeding 70 U/ml. AITD was detected in 12 of 50 patients (24 %). The levels of 25(OH) vitamin D were significantly lower in women with PCOS and AITD when compared with women with PCOS and without AITD (p = 0.02). In women with AITD no correlation was found between 25(OH) vitamin D and TG-Ab (r = 0.48; p = 0.16), TPO-Ab (r = 0.43; p = 0.21), TSH (r = 0.38; p = 0.27), FT3 (r = -0.40; p = 0.25) and FT4 levels (r = -0.54; p = 0.10). These findings suggest that low levels of 25(OH) vitamin D were significantly associated with AITD in women with PCOS.