Association of Hypervitaminosis D with Thyroid Function in Euthyroid Adult Patients

Abstract

Aim: No study has investigated the effect of hypervitaminosis D on thyroid function. We aimed to analyze possible associations of hypervitaminosis D with thyroid function in levothyroxine-naive euthyroid patients. Material and Methods: Levothyroxine-naive euthyroid patients (>18-year-old) with 25(OH) vitamin D level of ≥88 ng/mL after supplementation were analyzed retrospectively. We grouped them as: Group 1, TSH increased above the range; Group 2, TSH increased but in normal range; Group 3, TSH decreased but in normal range; Group 4, TSH decreased below the range; Group A, TSH increased; and Group B, TSH decreased. Before/after levels of TSH, fT4, Ca, P, creatinine, and TSH-change, fT4-change, 25(OH) vitamin D (basal/post-treatment and change), basal AntiTPO levels, and vitamin D dose were analyzed. Results: TSH-change -0.19±1.03 mIU/L and fT4-change 0.015±0.17 ng/dL were insignificant in total(n=64). Post-treatment 25(OH) vitamin D, TSH-after, and TSH-change were higher in group 1(n=3) than in group 2(n=22), group 3(n=33), or group 4(n=6) (p