A new form of speudohypoparathyroidism type II with abnormal response to TRH: 37

Abstract

A 12 years old Turkish girl, was admitted for tetany. She had laboratory findings of hypoparathyroidism (inorganic serum phosphorus : 7,5 mg/dl; calcium : 2,2 mEq/1; magnesium : 1,8 mg/dl). Blood alkaline phosphatase was strikingly increased as was iPTH. She has a normal phenotype but had moderate mental retardation. X-rays studies showed diffuse osteoporosis. The renal response to parathyroid extract administration was studied under several conditions : 1) there was a marked rise in urinary CAMP excretions but no increase in urinary phosphates. This type of response caracterizes pseudohypoparathyroidism (PHP) type II. 2) calcium therapy and vitamin D therapy did not modify this response. 3) the absence of restoration of normal renal responsiveness after an acute calcium infusion differentiates this case from the one described by Rodriguez. There was an excessive thyrotropin response to TRH injection whereas other studies of thyroid function were normal. With very low doses of vit. D (2000 U/day), serum calcium returned rapidly to normal values but phosphorus remained high and the renal unresponsiveness to PTH was unchanged. The TRH response also remained impaired. We propose that this could be a new form of pseudohypoparathyroidism (type III ?) whose calcemia can be controlled by low doses of vit. D.