Effect of Zinc Supplementation on Thyroid Hormone Metabolism of Adolescents with Down Syndrome

Studies have evidenced that zinc metabolism is altered in the presence of Down syndrome, and zinc seems to have a relationship with the metabolic alterations usually present in this syndrome. In this work, the effect of zinc supplementation on thyroid hormone metabolism was evaluated in adolescents with Down syndrome. A prospective study was carried out on 16 adolescents with Down syndrome (age: 10–19 years) who were randomized for treatment with 30 mg zinc daily for 4 weeks. Diet evaluation was accomplished y using a 3-day dietary record, and the analysis was performed by the NutWin program, version 1.5. Anthropometric measurements were performed for evaluation of body composition. The Zn-related nutritional status of the groups was evaluated by means of zinc concentration determinations in plasma and erythrocytes using the method of atomic absorption spectroscopy, and the thyroid hormone was obtained by radioimmunoassay. The diet of patients with Down syndrome, before and after the intervention presented reduced energy level and adequate zinc concentrations. Mean plasma zinc values were 59.2 ± 13.2 and 71.0 ± 21.9 μg/dL before and after the intervention, respectively. Erythrocyte concentrations of the mineral before supplementation, instead, were 51.5 μg/dL ± 11.1 μg Zn/gHb, and at the end of the experiment, they were 42.9 ± 8/5 μg Zn/gHb, with a significant statistical difference (p 0.05). Intervention with zinc showed to be effective in the stabilization of the concentrations of this mineral in plasma and erythrocytes, but had no influence on the metabolism of thyroid hormones.