Definition: A disorder resembling hypoparathyroidism, with high serum phosphate and low calcium levels but with normal or elevated serum parathyroid hormone levels; the defect is due to lack of end-organ responsiveness to parathyroid hormone. There are two types: type I shows lack of renal tubular response to exogenous parathyroid hormone with increase in urinary cAMP, type Is has type I skeletal defects (syn Albright hereditary osteodystrophy), and type II is associated with a defect at a locus after cAMP production. X-linked dominant inheritance caused by mutation in the gene encoding guanine nucleotide-binding protein α-stimulating activity polypeptide 1 (GNAS1), which regulates adenyl cyclase on chromosome 20q.
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Examples: glitazone, GI cocktail, etc.