Pseudohypoparathyroidism type 1a presenting as congenital hypothyroidism

PSEUDOHYPOPARATHYROID1SM TYPE 1 is an inherited metabolic disorder characterized by hypocalcemia and hyperphosphatemia, which are caused by end organ resistance to the action of PTH?. 2 Most of these patients have, in addition, the skeletal abnormalities of Albright hereditary osteodystrophy. 2 The molecular basis for the resistance to PTH in most patients ( P H P l a ) is an impairment in c A M P synthesis 3 caused by deficient activity of guanine nucleotide regulatory protein of adenylate cyclase (Nprotein), 4-7 a plasma membrane protein that couples hormone receptors to the catalytic uni t of adenylate cyclase. 8 The localization of the defect distal to the hormone receptor implies that resistance to other hormones that act via c A M P may occur in PHP-1. Indeed, resistance to TSH, glucagon, ADH, and gonadotropins has been demonstrated in patients with PHP-1.6, 7 We describe a child in whom hypothyroidism was diagnosed shortly after birth; at the age of 5 years, a diagnosis of PHP-1 a was made.