Vitamin A deficiency (VAD) and the iodine deficiency disorders (IDD) affect more than 30% of the global population . These deficiencies often coexist in many areas of rural Africa 32–50% of school-age children suffer from both VAD and goiter. In areas of endemic goiter, micronutrient status can be an important determinant of iodine and thyroid metabolism . Deficiencies of selenium and iron can act in concert with iodine deficiency to impair thyroid function . Vitamin A status also affects thyroid metabolism. In animals, VAD increases thyroid size and increases circulating thyroid hormone levels . In the pituitary, retinoic acid suppresses transcription of the thyrotropin (TSH) gene , thereby reducing TSH secretion. To investigate the potential interactions between these two common deficiencies, we recently studied children from rural villages in the Brikcha region of the Rif Mountains of northern Morocco. Our study aims were: to investigate the effects of VAD on thyroid metabolism in an area of severe IDD; and to compare the efficacy of iodized salt alone to iodized salt given with VA supplementation . A small local cooperative supplies nearly all salt for the study region, producing it in drying ponds using water from a salty spring. Although Morocco legislated mandatory salt iodization in 1997, because of financial constraints this cooperative has not yet begun iodization.
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