Physiology Synthesis PTH is synthesized and secreted by the chief cells of parathyroid gland PTH is secreted in response to hypocalcemia hypomagnesemia Function PTH secretions leads to an ↑ serum Ca2+ ↑ bone resorption of calcium PTH receptor is on the osteoblasts which secretes IL-1 to activated osteoclasts ↑ kidney resorption of calcium in distal convoluted tubule ↑ 1,25-(OH)2 vitamin D production ↓ serum phosphate ↑ bone resorption of phosphate (bone is destroyed) ↓ kidney resorption of phosphate Clinical Conditions hypoparathyroidism hyperparathyroidism