The Acute Effects of 1,25-Dihydroxycholecalciferol on Serum Immunoreactive Parathyroid Hormone in the Dog*

Abstract

There is considerable evidence which suggests that the parathyroid gland may be a target for vitamin D metabolites. To investigate the effects of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on parathyroid hormone (PTH) secretion, the serum concentrations of immunoreactive PTH (IPTH), calcium, and phosphate were measured over a 12-h period after the single iv injection of 1 μg (2.4 nmol) 1,25(OH)2D3 in five normal and nine vitamin D-deficient puppies. In the vitamin Ddeficient animals, the mean serum calcium increased significantly by 8 h, and at 12 h was approximately 1 mg/dl above the basal value. Serum phosphate concentrations showed no significant change after 1,25(OH)2D3. An acute, transient increase in serum IPTH concentration followed the injection of 1,25(OH)2D3 in most but not all of the vitamin D-deficient puppies. However, the increase was not statistically significant in the mean serum IPTH concentration for the group. At 12 h, the mean IPTH concenration had decreased significantly from the bas...