Effects of administration of iron, iodine and simultaneous iron-plus-iodine on the thyroid hormone profile in iron-deficient adolescent Iranian girls

Abstract

To investigate whether iron supplementation can improve thyroid hormone function in iron-deficient adolescent girls. A double-blind randomized intervention study. The study was performed from 2002 through 2003 in the Islamic Republic of Iran. 103 iron-deficient non-anaemic girls who fulfilled all inclusion criteria were included, and 94 subjects successfully completed the study. Patients were randomly assigned to one of four groups and treated with a single oral dose of 190 mg iodine plus 300 mg ferrous sulphate 5 times/week (n=24), 300 mg ferrous sulphate 5 times/week (n=23), a single oral dose of 190 mg iodine (n=25), or a placebo (n=22) for 12 weeks. All groups were comparable at baseline. After the intervention, there was a significant increase in ferritin and transferrin saturation in the iron+iodine group (17.6 vs 8.7 microg/dl, and 18.8 vs 7.2%, respectively, P<0.001 for both) and in the iron group (P<0.001 for both). Urinary iodine doubled in the iron+iodine group and in the iodine group (P<0.001 for both). Thyroid indices tT4, tT3 and T3RU increased and reverse RT3 decreased in the iron+iodine group (10 vs 8.9 microg/dl, P< 0.001; 143 vs 138 microg/dl, P<0.05; 32.3 vs 28.4%, P<0.001 and 24.8 vs 44.2 ng/dl, P<0.001, respectively) and in the iron group. These two groups did not differ for any of the four indices, but both differed significantly from the iodine and placebo groups. Our results indicate that improvement of iron status was accompanied by an improvement in some indices of thyroid hormones. This study was supported by the Dean of Research Affairs of the Tehran University of Medical Sciences.