Effect of Iodine Supplementation on Iodine Status, Thyroid Function, Body Composition, and Resting Metabolic Rate in Women

Abstract

Decreased dietary iodine intake may predispose women to increased body weight and thyroid dysfunction. Purpose: to investigate efficacy of iodine supplementation in 18-45 year old women diagnosed with iodine deficiency in improving thyroid function, body composition and increasing resting metabolic rate (RMR) during a 6-month randomized, double-blind placebo-controlled trial. Study: non-pregnant women without a history of thyroid disease were randomized into two groups: iodine (IG, n=65, Iodoral® 12.5 mg iodine) or placebo (PG, n=38, glucose). Assessments included body mass index (BMI), RMR, body composition analysis (Dual Energy X-ray Absorptiometry-DXA), 24-hour urinary iodine (UI), % iodine saturation (IS), sodium iodide symporter (NIS) ratio, and concentrations of free thyroxine (T4), free triiodithyronine (T3), thyroid stimulating hormone (TSH) and thyroid-peroxidase antibody (TPOab). Baseline data (N=108) showed mean UI of 35.52mg/24hr vs >44 mg/24hr mean % IS 70.93% vs >90% and mean NIS ratio 27.86 vs 28-74, between study population and expected mean, respectively, indicating iodine deficiency. Of those completing study (n=35), UI increased from 34.1 to 37.7 mg/24hr (p=0.29) in IG (n=10) vs 32.0 to 34.8 mg/24hr (p=0.21) in PG (n=19), % IS increased from 67 to 75% (p=0.28) in IG (n=10) vs 63 to 70 (p=0.17) in PG (n=19), NIS ratio increased from 26.7 to 37.1 (p=0.16) in IG (n=10) vs 30.2 to 34.8 (p=0.34) in PG (n=18), and RMR increased from 1541 to 1595.5 Kcals (p=0.04) in IG (n=14) vs 1594-1643 Kcals (p=0.62) in PG (n=21). Iodine supplementation may improve iodine status, thyroid function and RMR in young women.