Renal adenylate cyclase assay for biologically active parathyroid hormone: clinical utility and physiological significance

Abstract

The stimulation of cyclic AMP production by human renal cortical membranes in the presence of the GTP analogue 5′-guanylimidodiphosphate and a calcium chelator represents a homologous assay system for the evaluation of biologically active parathyroid hormone (bioPTH) in human serum. Bioactive PTH was raised above normal (normal range: undetectable to 4·6 pmol human PTH(1–34) per 1) in 13/17 (76%) patients with primary hyperparathyroidism, in 5/6 (83%) patients with surgically proven hyperparathyroidism secondary to chronic renal failure, in 4/5 (80%) patients with hyperparathyroidism secondary to hypocalcaemia, in all three patients with pseudohypoparathyroidism, in 5/17 (29%) patients with osteoporosis and in 1/9 (11%) patients with renal stones and/or hypercalciuria. Bioactive PTH correlated positively with immunoreactive PTH (iPTH) measured with a radioimmunoassay predominantly recognizing the middleand carboxyl-terminal region of the PTH molecule (r = 0·503, Pr = 0·572, PPr = 0·390, PJ. Endocr. (1986) 108, 9–15