Porto-systemic gradient of immunoreactive parathyroid hormone in man

Systemic and portal levels of immunoreactive parathyroid hormone (iPTH) were evaluated as possible tumor markers for intraabdominal neoplasms in 170 patients. There was no significant difference between the systemic levels of iPTH in patients with pancreatic cancer, other intraabdominal tumors, or benign abdominal conditions. The portal iPTH levels were also comparable. In all patient groups the portal iPTH levels were consistently higher than the systemic levels; the mean portal iPTH for all patients was 31.3 ± 1.3 (SEM) μ l-eq/ml, significantly higher than the systemic level of 27.2 ± 1.1 μ l-eq/ml ( P t test). We conclude that iPTH is of no diagnostic value as a tumor marker in either portal or systemic blood. Our observations suggest a site of iPTH synthesis in the gastrointestinal tract drained by the portal venous system. APUD cells of the pancreas or gut are considered possible production sites of iPTH, and liver degradation of the hormone probably occurs in man.