Deficient activity of receptor-cyclase coupling protein in platelets of patients with pseudohypoparathyroidism.

Erythrocytes of patients with pseudohypoparathyroidism exhibit decreased activity of a membrane protein that is required for functional coupling of hormone receptors and catalytic adenylate cyclase. We observed decreased activity of this coupling protein in platelet extracts obtained from two pseudohypoparathyroid subjects, as compared with those of four normal control subjects. These findings support the hypothesis that generalized deficiency of this coupling protein is the primary biochemical defect of pseydohypoparathyroidism.