Effect of Dibutyryl Adenosine 3',5'-monophosphate Administration on Plasma Concentrations of 1,25-dihydroxyvitamin D in Pseudohypoparathyroidism Type I

The effect of dibutyryl cAMP on plasma concentrations of 1,25-dihydroxyvitamin D [1,25-(OH)2D] was studied in two patients with pseudohypoparathyroidism (PHP) type I, five normal adults, and three normal children as controls. In normal adults, plasma 1,25-(OH)2D tended to increase 3 h after the infusion of 2.5 mg/kg dbcAMP and was significantly increased after 6 h. In normal children, plasma 1,25-(OH)2D increased 3 h after the infusion, then gradually decreased; in the patients with PHP type I, it increased greatly from 6.8 and 11.2 pg/ml to 264.6 and 128.2 pg/ml 3 h after the infusion. These results suggest that the renal mechanism for the response to parathyroid hormone is intact distal to the renal adenylate cyclase in patients with PHP type I.