Metabolism of human PTH by the kidney and the liver

Immunoreactive PTH was measured by amino terminal and carboxyl terminal specific assays in the femoral artery, the right renal vein and the suprahepatic vein of ten hyperparathyroid patients. A marked arterio venous difference for amino terminal immunoreactivity was observed in the kidney and the liver. In contrast, the arterio venous difference for carboxyl terminal immunoreactivity was small in the kidney and not significantly in the liver. It is concluded that intact PTH and possibly amino terminal fragments of the hormone are metabolized by the kidney and the liver. Considering the fact that a carboxyl terminal specific antiserum is also capable of recognizing intact hormone, the finding of a small positive arterio venous difference for carboxyl terminal immunoreactivity does not permit us to exclude the possibility that the kidney and/or the liver are capable of generating carboxyl terminal fragments.