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The Effects of Vitamin A Deficiency and Vitamin A Supplementation on Thyroid Function in Goitrous Children

Human Nutrition Laboratory, Swiss Federal Institute of Technology Zurich (M.B.Z., R.W., C.Z.), CH-8803 Ruschlikon, Switzerland; Ministry of Health (N.C.), Rabat, Agdal-10000 Morocco; and Department of Endocrinology, University Children’s Hospital (T.T.), CH-8032 Zurich, Switzerland

Address all correspondence and requests for reprints to: Dr. M. Zimmermann, Human Nutrition Laboratory, Swiss Federal Institute of Technology Zurich, Seestrasse 72/Postfach 474, CH-8803 Ruschlikon, Switzerland. E-mail: michael.zimmermann{at}ilw.agrl.ethz.ch.

In developing countries, children are at high risk for both the iodine deficiency disorders (IDD) and vitamin A deficiency (VAD). The study aim was to determine the effects of VAD and vitamin A (VA) supplementation on thyroid function in an area of endemic goiter. In a double-blind, randomized, 10-month trial, Moroccan children with IDD and VAD (n = 138) were given iodized salt and either VA (200,000 IU) or placebo at 0 and 5 months. At 0, 5, and 10 months, measurements of VA status and thyroid function were made. At baseline, increasing VAD severity was a predictor of greater thyroid volume and higher concentrations of TSH and thyroglobulin (P < 0.001). In children with VAD, the odds ratio for goiter was 6.51 (95% confidence interval, 2.94, 14.41). VAD severity was also a strong predictor of higher concentrations of total T₄ (P < 0.001); the odds ratio for hypothyroidism in VAD was 0.06 (95% confidence interval, 0.03, 0.14). During the intervention, mean thyroglobulin, median TSH, and the goiter rate significantly decreased in the VA-treated group compared with those in the placebo group (P < 0.01). The findings indicate that VAD in severely IDD-affected children increases TSH stimulation and thyroid size and reduces the risk for hypothyroidism. This effect could be due to decreased VA-mediated suppression of the pituitary TSHß gene. In IDD- and VAD-affected children receiving iodized salt, concurrent VA supplementation improves iodine efficacy.

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