Pseudohypoparathyroidism.

The current understanding of the adenylate cyclase complex has permitted us to regard PHP has a heterogeneous group of disorders related to each other through the common feature of resistance to PTH. Patients may present with hormone resistance limited to PTH, or with a metabolic disorder attributable to the resistance of multiple tissues to hormones that activate adenylate cyclase. The majority of the latter patients show deficient G-unit activity. The clinical expression of multiple hormone resistance in patients with the G-unit defect appears to be rather variable, despite an identical quantitative defect; hormone resistance seems incomplete, and patients may be hypocalcemic despite the presence of hyperparathyroid bone disease. It is therefore likely that the detailed biochemical study of patients with PHP may ultimately reveal a multiplicity of abnormalities in the hormone-receptor adenylate cyclase system that will explain the variability of hormone resistance.