Demonstration of a Lack of Change in Serum la,25-Dihydroxyvitamin D in Response to Parathyroid Extract in Pseudohypoparathyroidism

effects of parathyroid extract (PTE) on serum and uri-nary calcium (Ca) and phosphorus (P), serum 25-hy-droxyvitamin D (25-OHD), serum 24,25-dihydroxyvita-min D (24,25(OH)2D), serum la,25-dihydroxyvitamin D (la,25(OH)2D), and urinary cyclic AMP in two nor-mal subjects, two patients with hypoparathyroidism (HP) and six patients with pseudohypoparathyroidism (PHP), some of whom were on suboptimal treatment with vitamin D. Two of the patients with PHP were studied while on long-term treatment with la,25-(OH)2D3. Before PTE, serum la,25(OH)2D was at the lower limit ofnormal in one patient and was abnormally low in the other five patients. None ofthese individuals was on treatment with la,25(OH)2D3. Serum 25-OHD and 24,25(OH)2D were either increased or at the upper limit ofnormal in the patients given vitamin D and were normal in the other patients. PTE lowered the serum P and increased the serum la,25(OH)2D, serum and uri-nary Ca, urinary P, and urinary cyclic AMP in the nor-mal subjects and patients with HP. In individual studies, changes in serum la,25(OH)2D and serum Ca occurred in parallel before, during, and after PTE. In contrast, PTE had very little effect in the patients with PHP. Whereas there were highly significant positive correlations between serum 1a,25(OH)2D and serum Ca, and highly significant negative correlations be-tween serum P and serum la,25(OH)2D in each of the normal subjects and patients with HP, there were sig-nificant correlations in only one of the patients with PHP. An increase in serum Ca in response to PTE wa