Regulatory hyperparathyroidism in a pig breed with vitamin D dependency rickets.
A radioimmunoassay for porcine parathyroid hormone has been developed and applied to measure immunoreactive parathyroid hormone (PTH) in plasma of pigs with hereditary vitamin D dependency rickets (VDDR) (pseudovitamin D deficiency rickets). Levels of 25-hydroxycholecalciferol (25-(OH)-D3) in plasma were measured by a protein binding assay. Both plasma concentrations of PTH and 25-(OH)-D3 showed an approximately 4-fold increase compared to normal pigs. PTH levels increased with duration of the disease. Daily dosing of the animals with 1--4 micrograms of 1,25-dihydroxycholecalciferol (1,25-(OH)2-D3) reduced PTH concentrations and resulted in clinical healing. Iv administration of 10 micrograms of 25-(OH)-D3/day did not alter PTH concentrations nor the clinical symptoms. The results suggest that these animals suffer from regulatory hyperparathyroidism. The metabolic defect could be due to a failure of the kidney to convert 25-(OH)-D3 to 1,25-(OH)2-D3.
D000818:Animals; D002417:Cattle; D006168:Guinea Pigs; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood / Q000627:therapeutic use; D006961:Hyperparathyroidism / Q000188:drug therapy / Q000209:etiology / Q000662:veterinary*; D007106:Immune Sera; D007457:Iodine Radioisotopes; D010281:Parathyroid Hormone / Q000097:blood*; D011863:Radioimmunoassay; D012279:Rickets / Q000097:blood / Q000150:complications / Q000662:veterinary*; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy / Q000235:genetics*
D006887:Hydroxycholecalciferols; D007106:Immune Sera; D007457:Iodine Radioisotopes; D010281:Parathyroid Hormone