Katacalcin: a new plasma calcium-lowering hormone.

A second potent plasma calcium-lowering peptide, katacalcin (PDN-21), flanks calcitonin within the human calcitonin precursor. Plasma katacalcin was present in 57 healthy volunteers. Concentrations were higher in males than in females and approximately equimolar with calcitonin. Plasma katacalcin doubled within 5 min of calcium infusion. Plasma katacalcin was markedly raised in 20 patients with medullary carcinoma of the thyroid. Measurement of plasma katacalcin concentrations may prove useful in the diagnosis and follow-up of this condition. Katacalcin, like calcitonin, may be involved in both plasma calcium regulation and skeletal maintenance and thus may prove useful in the treatment of bone disease.