Parathyroid Hormone Secretion (PTH Secretion)

Parathyroid hormone (PTH) secretion refers to the process by which the parathyroid glands release PTH into the bloodstream. PTH is a key regulator of calcium and phosphate homeostasis in the body, acting primarily on bone, kidneys, and indirectly on the gut. When blood calcium levels drop (hypocalcemia), parathyroid glands secrete more PTH. When blood calcium levels rise (hypercalcemia), PTH secretion is suppressed. This regulation occurs via a negative feedback loop involving specialized cell-surface calcium-sensing receptors (CaSR) on parathyroid cells. The mechanism involves exocytosis: vesicles containing preformed PTH fuse with the cell membrane to release hormone into circulation.