Effect of Vitamin D Supplementation on Muscle Function in Patients With I131-Induced Hypothyroidism: A Pilot Randomized Trial.

Background: There is a lack of data regarding the effect of vitamin D supplements in patients with I131-induced hypothyroidism. The primary aim of this study was to investigate the effect of vitamin D supplements on muscle function, and the secondary aim was to observe the effect on body composition, insulin resistance, and quality of life (QOL) in patients with I131-induced hypothyroidism. Methods: In this pilot randomized placebo-controlled trial, patients with I131-induced hypothyroidism on a stable dose of levothyroxine were enrolled and allocated into 2 groups to receive oral vitamin D 20 000 IU weekly or placebo for 24 weeks. Baseline biochemical values, body composition, handgrip strength, the 5 times sit-to-stand test (5TSTS), homeostatic model assessment for insulin resistance (HOMA-IR), and QOL were measured before intervention and after 3 and 6 months in both groups. Mixed model regression analysis was used to compare the outcomes between the 2 groups. Significance was set at P value of < .05. Results: There were 20 participants in each group. The time taken for 5TSTS in the vitamin D group was significantly lower than the placebo group at 3 (P = .032) and 6 months (P = .006). Other outcomes, including handgrip strength, body composition, HOMA-IR, and QOL, showed no significant difference between the 2 groups. Conclusion: A supplement of vitamin D2 at 20 000 IU per week for 24 weeks could help improve performance in 5TSTS in patients with I131-induced hypothyroidism.