Parathyrin Radioimmunoassay: Diagnostic Utility of Antisera Produced against Carboxyl-terminal Fragments of the Hormone

Antisera directed toward the carboxyl-terminal region of human parathyrin (parathyroid hormone), for use in diag-nostically applicable radioimmunoassays of the hormone in serum, are scarce, largely because of the lack of suit-able immunogens of human origin. We produced four an-tisera in goats and guinea pigs by immunization with re-cently discovered carboxyl-terminal fragments of human parathyrin extracted from parathyroid tumors. Here, we report results of radioimmunoassays of nearly 200 normal and pathological sera with one of these antisera; we ob-served almost complete differentiation between concen-trations of parathyrin in serum of healthy normal subjects and patients with primary, secondary (due to chronic renal failure), or “ectopic ” hyperparathyroidism (due to non-parathyroid cancer). The availability of a new immunoge