Studies to Determine the Usefulness of the Zinc Clearance Test to Diagnose Marginal Zinc Deficiency and the Effects of Oral Zinc Supplementation for Short Children

Abstract

Objective: To evaluate the usefulness of the body zinc clearance test in the diagnosis of marginal zinc deficiency and to estimate the efficacy of oral zinc supplementation on growth in short children.Methods: Zinc status was evaluated in 30 (19 boys and 11 girls) Japanese children with short stature using the body zinc clearance test. Changes in growth after oral zinc supplementation (ZnSO4 · 7H2O; 5 mg/kg/day in two divided doses) were studied.Results: Basal serum zinc concentrations were 75.0±12.7 μg/dl and zinc clearance values were 19.1±5.8 ml/kg/hour in the 30 subjects. The correlation coefficient between serum zinc concentrations and zinc clearance values was as small as −0.36. There were nine cases whose body zinc clearance values were high and serum zinc concentrations were low, indicating definite zinc deficiency. There were nine cases whose body zinc clearance values were high, despite normal serum zinc concentrations, indicating marginal zinc deficiency. The mean height velocity for males was 5.3 cm/year before zinc supplementation and 7.8 cm/year after the therapy; and the mean SD score for height for age improved from −1.85 to −1.53. The mean height velocity for females was 5.1 cm/year before zinc supplementation and 5.9 cm/year after the therapy, and the mean SD score for height for age changed from −2.02 to −2.03.Conclusion: The body zinc clearance test was much more useful than serum zinc concentrations in diagnosing marginal zinc deficiency. Oral zinc supplementation improved the height velocity in short males, but not in short females.