Background: Vitamin D acts as immunomodulatory molecule and its deficiency has been implicated in various autoimmune diseases including immune mediated hypothyroidism. However, its association with thyroid hormones is ambiguous. The present study was therefore aimed to explore the relationship of vitamin D with thyroid hormone levels in a population enrolled for health care check up in a tertiary care hospital.
Methods: The present cross-sectional study included 664 subjects. Serum levels of 25(OH) vitamin D, free triiodothyronine, free thyroxine, and thyroid stimulating hormone (TSH) were measured. Serum vitamin 25(OH)D levels < 30 ng/mL and > 30 ng/mL were considered as vitamin D insufficient and vitamin D sufficient state, respectively.
Results: Vitamin D insufficiency was greater in females (89.6%) than in males (78.5%). Females were observed to have significantly lower serum 25(OH)D levels (18.7 ± 9.5 versus 20.62 ± 10.2 ng/mL) and higher serum TSH values (2.5 ± 1.25 versus 2.25 ± 1.16 mIU/L) as compared to males. The serum TSH level in the vitamin D sufficiency group were significantly lower than those in the vitamin D insufficiency group (2.39 ± 1.22 versus 2.12 ± 1.1 mIU/ L). Further, age was the only significant predictor of TSH levels. Meanwhile, no predictor was identified for vitamin D levels.
Conclusions: Although no association was observed between TSH and vitamin D levels, TSH was observed to be significantly higher in the vitamin D insufficient group than the vitamin D sufficient group. It warrants further studies to ascertain the role of vitamin D in regulating thyroid hormones considering the thyroid autoimmune status of the individuals as well.