Effect of zinc supplementation on thyroid hormone function - A case study of two college females

Background/ Aims: Zinc is crucial for proper thyroid hormone metabolism; zinc deficiency may result in decreased thyroid hormone levels and resting metabolic rate ( RMR). The purpose of this investigation was to assess the effects of zinc supplementation on plasma zinc, serum ferritin, plasma total triiodothyronine ( T-3) and thyroxine ( T-4), serum free T-3 and T-4, and thyroid- stimulating hormone concentrations, and RMR in zinc- deficient, physically active women. Methods: Two zinc- deficient female college students ( ZD1 and ZD2) were supplemented with 26.4 mg/ day of zinc ( as zinc gluconate), and the above parameters were analyzed at 0, 2 and 4 months. Results: Zinc deficiency was clinically corrected in both subjects, while serum ferritin concentration declined to classify both subjects as borderline iron deficient ( ZD1 = 15.3 and ZD2 = 15.3 ng/ ml at 4 months). At 4 months, total T 3 concentrations increased in ZD1, while all thyroid hormone concentrations increased in ZD2. RMR increased in both subjects by 4 months. Conclusion: Zinc supplementation appeared to be directly responsible for the increase in plasma zinc and decline in serum ferritin concentrations in both subjects. Zinc supplementation appeared to have a favorable effect on thyroid hormone levels, particularly total T 3, and RMR. Copyright (c) 2007 S. Karger AG, Basel.