Stimulation of 1,25-dihydroxyvitamin D production by parathyroid hormone and dibutyryl 3',5'-cyclic AMP in normal subjects,hypoparathyroidism and pseudohypoparathyroidism.

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Abstract
UNAKAMI, H., FURUKAWA, Y., SOHN, H.E., YUMITA, S., MIURA, R., HANEW, K. and YOSHINAGA, K. Stimulation of 1, 25-Dihydroxyvitamin D Production by Parathyroid Hormone and Dibutyryl 3', 5'-Cyclic AMP in Normal Subjects, Hypoparathyroidism and Pseudohypoparathyroidism. Tohoku J. exp. Med., 1982, 138 (2), 167-175 Parathyroid extract (PTE) or synthetic 1-34 human parathyroid hormone (1-34hPTH) was injected intravenously as a bolus in 4 normal subjects, 4 patients with PTH deficient hypoparathyroidism (HP) and 3 patients with pseudohypoparathyroidism (PHP). In normal subjects and HP, plasma 1, 25(OH)2D was markedly increased at 6hr and reached the peak at 12 or 14hr after administration of 200 units of PTE or 20 to 30μg of 1-34hPTH. On the other hand, 500 units of PTE or 20μg of 1-34hPTH failed to increase plasma 1, 25(OH)2D in PHP. However, 2.5mg/kg of dibutyryl cAMP remarkably increased plasma 1, 25(OH)2D in a patient with PHP. Maximal increments of plasma 1, 25(OH)2D in 3 patients with HP (21.7±5.6pg/ml, mean±S.D.) were nearly as high as in normal subjects (20.6±7.0pg/ml), whereas those in 3 patients with PHP (2.3±2.3pg/ml) were distinctly lower than in normal subjects or HP. It is suggested that 1, 25(OH)2D production by PTH is intact in HP, but is impaired in PHP mainly due to a defect in the activation of adenylate cyclase system.