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Children with vitamin A and iodine deficiency have less severe hypothyroidism and more goiter than those with iodine deficiency alone
The background of the study. Worldwide, iodine
deficiency and vitamin A deficiency are common. In this study the
effects of iodine and vitamin A deficiency on thyroid function were
determined in a group of Moroccan children. Some children were studied
again after iodine supplementation with and without vitamin A supplementation.
How the study was done. The initial study subjects were 298 children who lived in rural Morocco. Their nutrition was adequate and no child had signs of vitamin A deficiency (xerophthalmia). Thyroid volume was measured by ultrasonography. Iodine was measured in urine samples, thyrotropin (TSH) in blood spots, and retinol, thyroxine (T4), and thyroglobulin in serum.
The supplementation study was done in 138 children with vitamin A deficiency. They were randomly divided by household into two groups. One was given 200,000 IU of vitamin A, and the other a placebo at base line and 5 months; the households of both groups were provided with salt fortified with iodine (25 µg/g).
The results of the study. Among the 298 children, 265 (89 percent) had a goiter; their mean urinary iodine excretion was low (10 µg/L). Fifty children (17 percent) had vitamin A deficiency, and 149 (50 percent) had low vitamin A status. Vitamin A deficiency was associated with higher blood-spot TSH concentrations, higher serum T4 and thyroglobulin concentrations, and thyroid enlargement.
Among the children in the treatment study, urinary iodine excretion increased 10-fold in both groups, and vitamin A status improved in the vitamin A group. The blood-spot TSH values decreased more in the iodine–vitamin A group than in the iodine–placebo group, as did thyroid volume, and serum thyroglobulin.
The conclusions of the study. Children with iodine deficiency and vitamin A deficiency have higher TSH and T4 concentrations and more thyroid enlargement, as compared with children with iodine deficiency alone. Supplementation with both is more effective in improving thyroid function and decreasing goiter than is supplementation with iodine alone.
The original article. Zimmermann MB, Wegmuller
R, Zeder C, Chaouki N, Torresani T. The effects of vitamin A deficiency
and vitamin A supplementation on thyroid function in goitrous children.
J Clin Endocrinol Metab 2004;89:5441-7.
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| Thyroid Digest Index | | | March 2005 Thyroid Digest |
