The Association Between Low Vitamin D Status and Autoimmune Thyroid Disease in Korean Premenopausal Women: The 6th Korea National Health and Nutrition Examination Survey, 2013-2014

Background: This study aimed to analyze the association of low vitamin D status with thyroid autoimmunity and dysfunction in the Korean population according to sex and menopausal status in women.

Methods: This study was based on the data acquired from the 6th Korea National Health and Nutrition Examination Survey. We enrolled 4,356 subjects who had data of thyroid function, antithyroid peroxidase antibody (TPOAb), and serum 25-hydroxyvitamin D (25[OH]D) levels. We excluded subjects who were pregnant and who had a history of thyroid disease or thyroid cancer, and those with transient thyroid dysfunction who tested negative for TPOAb (TPOAb[-]).

Results: TPOAb positivity (TPOAb[+]) with thyroid dysfunction (subclinical and overt hypothyroidism) was more prevalent in the vitamin D deficient group than in the vitamin D insufficient and sufficient groups including premenopausal (P=0.046) and postmenopausal women (P=0.032), although no significant differences were observed in men. The mean serum 25(OH)D level was significantly lower in the TPOAb(+) with thyroid dysfunction group than in the TPOAb(+) with euthyroidism and TPOAb(-) groups of premenopausal women (P=0.001), although no significant differences were observed in men and postmenopausal women. Multivariate binary logistic regression analysis, adjusted for age, body mass index, and current smoking status, showed that vitamin D insufficiency and deficiency were significantly associated with TPOAb(+) with thyroid dysfunction in premenopausal women (P<0.001), although no significant associations were observed in men and postmenopausal women.

Conclusion: Low vitamin D status was significantly associated with thyroid autoimmunity and dysfunction in the Korean population, especially in premenopausal women.