Effect of calcium administration on renal responsiveness to parathyroid hormone in pseudohypoparathyroidism type I and II - In comparion with normals, idiopathic and surgical hypoparathyroidism.

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Abstract
A 31-yr-old man and a 12 yr-old girl were diagnosed as psuedohypoparathyroidism (PHP) Type I because of a failure to respond to the administration of parathyroid hormone (PTH) with increased urinary excretion of phosphate and cyclic (c)AMP. A 22-yr-old woman was diagnosed as PHP Type II because there was no increase in the urinary excretion of phosphate despite a marked increase in urinary cAMP excretion. With the combined Ca-PTH infusion or PTH infusion after vitamin D therapy, renal response was improved in these patients. Also dibutyryl (db)cAMP infusion evoked an increased urinary phosphate excretion in all of the patients. The metabolic defect of our patients with PHP Type I may be caused not by a lack or defective form of PTH-sensitive receptor adenylate cyclase complex, but rather by an abnormal conformation in the plasma membrane-associated receptor adenylate cyclase enzyme complex in kidney. In the patient with PHP Type II, as cAMP generation is intact, the metabolic defect might be related to a defect of calcium mobilization in renal tubular cells in response to PTH.

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