ZINC STATUS AND SERUM TESTOSTERONE LEVELS OF HEALTHY-ADULTS

Zinc deficiency is prevalent throughout the world, including the USA. Severe and moderate deficiency of zinc is associated with hypogonadism in men. However, the effect of marginal zinc deficiency on serum test osterone concentration is not known. We studied the relationship betwe en cellular zinc concentrations and serum testosterone cross-sectional ly in 40 normal men, 20 to 80 y of age, In four normal young men (27.5 +/- 0.5 y). we measured serum testosterone before and during marginal zinc deficiency induced by restricting dietary zinc intake. We also m easured serum testosterone in nine elderly men (64 +/- 9 y) who were m arginally zinc deficient before and after 3 to 6 mo of supplementation with 459 mu mol/d oral zinc administered as zinc gluconate. Serum tes tosterone concentrations were significantly correlated with cellular z inc concentrations in the cross-sectional study (lymphocyte zinc versu s serum testosterone, r = 0.43, p = 0.006: granulocyte zinc versus ser um testosterone, r = 0.30, p = 0.03). Dietary zinc restriction in norm al young men was associated with a significant decrease in serum testo sterone concentrations after 20 weeks of zinc restriction (baseline ve rsus post-zinc restriction mean +/- SD, 39.9 +/- 7.1 versus 10.6 +/- 3 .6 nmol/L, respectively; p = 0.005). Zinc supplementation of marginall y zinc-deficient normal elderly men for six months resulted in an incr ease in serum testosterone from 8.3 +/- 6.3 to 16.0 +/- 4.4 nmol/L (p = 0.02). We conclude that zinc may play an important role in modulatin g serum testosterone levels in normal men.