Effect of Vitamin D on Thyroid Autoimmunity: A Randomized, Double-Blind, Controlled Trial Among Ethnic Minorities

Kirsten V Knutsen; Ahmed A Madar; Mette Brekke; Haakon E Meyer; Åse Ruth Eggemoen; Ibrahimu Mdala; Per Lagerløv

doi:10.1210/js.2017-00037

Effect of Vitamin D on Thyroid Autoimmunity: A Randomized, Double-Blind, Controlled Trial Among Ethnic Minorities

J Endocr Soc. 2017 Apr 11;1(5):470-479. doi: 10.1210/js.2017-00037. eCollection 2017 May 1.

Authors

Kirsten V Knutsen¹, Ahmed A Madar², Mette Brekke¹, Haakon E Meyer^{2

3}, Åse Ruth Eggemoen¹, Ibrahimu Mdala¹, Per Lagerløv¹

Affiliations

¹ Department of General Practice, Institute of Health and Society, University of Oslo, 0318 Oslo, Norway.
² Department of Community Medicine and Global Health, Institute of Health and Society, University of Oslo, 0318 Oslo, Norway.
³ Division of Epidemiology, Norwegian Institute of Public Health, 0403 Oslo, Norway.

Abstract

Context: Autoimmune thyroid disorders have been linked to vitamin D deficiency, but an effect of vitamin D supplementation is not established.

Objective: Our objective was to test whether vitamin D compared with placebo could reduce thyroid autoantibodies.

Design: Predefined additional analyses from a randomized, double-blind, placebo-controlled trial.

Setting: The study was conducted in different community centers in Oslo, Norway.

Participants: A total of 251 presumed healthy men and women, aged 18 to 50 years, with backgrounds from South Asia, the Middle East, and Africa were included.

Intervention: Daily supplementation with 25 µg (1000 IU) vitamin D₃, 10 µg (400 IU) vitamin D₃, or placebo for 16 weeks.

Outcome measure: Difference in preintervention and postintervention antithyroid peroxidase antibody (TPOAb) levels. Additional outcomes were differences in thyroid-stimulating hormone (TSH) and free fraction of thyroxine (fT4).

Results: There were no differences in change after 16 weeks on TPOAb (27 kU/L; 95% CI, -17 to 72; P = 0.23), TSH (-0.10 mU/L; 95% CI, -0.54 to 0.34; P = 0.65), or fT4 (0.09 pmol/L; 95% CI, -0.37 to 0.55; P = 0.70) between those receiving vitamin D supplementation or placebo. Mean serum 25(OH)D₃ increased from 26 to 49 nmol/L in the combined supplementation group, but there was no change in the placebo group.

Conclusion: Vitamin D₃ supplementation, 25 µg or 10 µg, for 16 weeks compared with placebo did not affect TPOAb level in this randomized, double-blind study among participants with backgrounds from South Asia, the Middle East, and Africa who had low vitamin D levels at baseline.

Keywords: autoimmune thyroid disease; ethnicity; randomized controlled trial; thyroid hormone; vitamin D.