Albright's hereditary osteodystrophy

Originally reported as a hypocalcemic syndrome similar to hypoparathyroidism, but with renal and skeletal resistance to parathyroid hormone (PTH) and designated as "pseudohypoparathyroidism." Albright later defined a normocalcemic variant which he termed "pseudopseudohypoparathyroidism." Two separate forms of pseudohypoparathyroidism are recognized. Type I in which there is no increase in the urinary excretion of cyclic adenosine monophosphate (cAMP) and phosphate in response to parathyroid hormone (PTH). Type II in which there is a response to PTH, but without phosphate diuresis. The erythrocytes of some patients with type I contain a defective receptor-cyclase coupling protein (stimulatory guanine nucleoside-binding protein, or GS) which is responsible for coupling the cellular receptor that binds parathyroid hormone (PTH) and is involved with the formation and release of cyclic adenosine monophosphate (cAMP). This variant has been designated as "pseudohypoparathyroidism type Ia." The syndrome is associated with mental deficiency, dystrophic bone lesions, short stature, and other defects.