Zinc metabolism in renal disease and renal control of zinc excretion.

Serum zinc concentrations are decreased in patients with a variety of clinical disorders including cirrhosis, nephrotic syndrome and renal insufficiency. Urinary zinc excretions are increased in the first two disease states. Symptoms of acute zinc deficiency (anorexia, dysfunction of smell and taste, and mental and cerebellar disturbances) and chronic zinc deficiency (growth retardation, anemia, testicular atrophy, and impaired wound healing) are common in these patients. It remains unresolved whether these disease states are indicative of true symptomatic or asymptomatic zinc deficiency or merely reflect a decrease in available zinc binding proteins. The low serum zinc concentrations and high urinary zinc excretions in patients with nephrotic syndrome do not appear to be due to loss of zinc bound to urinary proteins. Studies in dogs indicate increased serum and urine concentrations of certain amino acids(cysteine, histidine) greatly increase urinary zinc excretions. Studies are now underway to determine if the hyperzincuria and hypozincemia of cirrhosis, nephrotic syndrome and hyperalimentation can be explained by an increase in these urinary amino acids.