Iodine Supplementation Decreases Hypercholesterolemia in Iodine-Deficient, Overweight Women: A Randomized Controlled Trial

Background: In iodinedeficiency, thyrotropin (TSH)may increase to stimulate thyroidal iodineuptake. In iodine-sufficient populations, higher TSHpredicts higher total cholesterol.Whether higher TSH caused by iodine deficiency affects serum lipids is uncertain. Objective: Our aim was to determine if iodine repletion decreases serum TSH and improves the lipid profile. Methods: In this randomized controlled intervention, iodine-deficient, overweight or obese Moroccan women (n = 163) received 200 mg oral iodine or a placebo daily for 6 mo. Main outcomes were serum TSH and plasma total and LDL cholesterol. Secondary outcomes included thyroid hormones and measures of lipid and glucose metabolism and urinary iodine concentration (UIC). Data were compared by using mixed-model analysis. Results: In the intervention group, median UIC increased from 38 (95% CI: 34, 45) mg/L to 77 (95%CI: 59, 89) mg/L (P 5mmol/L) was reduced by 11%after the intervention (P= 0.034). At 6mo, only 21.5%of treatedwomen remained hypercholesterolemic (total cholesterol >5 mmol/L) vs. 34.8% of controls (baseline: 44.2% in the intervention and 36.8% in the control group; P = 0.015). The reduction in the prevalence of elevated LDL cholesterol (>3mmol/L) seen in the intervention group (50.6% to 35.4% compared with 47.4% to 44.9% in the control group) was not significant (P-interaction = 0.23). Conclusions: Our findings suggest that moderate to severe iodine deficiency in overweight women elevates serum TSH and produces a more atherogenic lipid profile and that iodine supplementation in this group reduces the prevalence of hypercholesterolemia. Thus, iodine prophylaxis may reduce cardiovascular disease risk in overweight adults. This trial was registered at clinicaltrials.gov as NCT01985204. J Nutr doi: 10.3945/jn.115.213439.