Parathyroid hormone clearance in man.

The role of the kidney, liver, and bone and/or muscle, in the metabolic clearance of parathyroid hormone (PTH), has been examined in man. Serum was obtained from the femoral artery and the renal, hepatic, and femoral veins of nine hyperparathyroid patients undergoing selective venous catheterization. The concentration of immunoreactive parathyroid hormone (IPTH) was measured in the samples by radioimmunoassay using an antiserum predominantly specific for the aminoterminal (N-terminal) portion of the PTH molecule. Gel filtration of hyperparathyroid sera demonstrated this antiserum to measure essentially only intact PTH. The mean arteriovenous (AV) difference measured across the liver was 44%; across the kidney, 34%; and across the leg, 16%. These arteriovenous differences were all statistically significant (p less than 0.005). A significant positive correlation was found between the AV difference in IPTH across the kidney and the serum calcium concentration (r = 0.50, p less than 0.05). These studies suggest that both the liver and the kidney play major roles in the clearance of PTH in man and indicate that PTH is cleared by bone and/or muscle as well. The correlation observed between the serum calcium concentrations and the AV differences in IPTH across the kidney suggest that the rate of clearance of PTH in man may be modulated by changes in the concentration of serum calcium.