The Effects of Vitamin D Supplementation on Thyroid Function in Hypothyroid Patients: A Randomized, Double-blind, Placebo-controlled Trial.

BACKGROUND

Data on the effects of vitamin D supplementation on thyroid function in hypothyroid patients are scarce.

OBJECTIVE

This study was done to evaluate the effects of vitamin D supplementation on thyroid function in hypothyroid patients.

MATERIAL AND METHODS

This randomized double-blind, placebo-controlled trial was conducted on 201 hypothyroid patients aged 20-60 years old. Subjects were randomly assigned into two groups to intake either 50,000 IU vitamin D supplements ( = 102) or placebo ( = 99) weekly for 12 weeks. Markers of related with thyroid function were assessed at first and 12 weeks after the intervention.

RESULTS

After 12 weeks of intervention, compared to the placebo, vitamin D supplementation resulted in significant increases in serum 25-hydroxyvitamin D (+26.5 ± 11.6 vs. 0.0 ± 0.0 ng/mL, < 0.001) and calcium (+0.4 ± 0.7 vs. 0.1 ± 0.6 mg/dL, = 0.002), and a significant decrease in serum thyroid-stimulating hormone (TSH) levels (-0.4 ± 0.6 vs. +0.1 ± 2.0 μIU/mL, = 0.02). A trend towards a greater decrease in serum parathyroid hormone (PTH) levels was observed in vitamin D group compared to placebo group (-3.8 vs. +1.9, = 0.07). We did not observe any significant changes in serum T3, T4, alkaline phosphatase (ALP) and albumin levels following supplementation of vitamin D compared with the placebo.

CONCLUSION

Overall, the current study demonstrated that vitamin D supplementation among hypothyroid patients for 12 weeks improved serum TSH and calcium concentrations compared with the placebo, but it did not alter serum T3, T4, ALP, PTH, and albumin levels.