Calcium homeostasis is a process controlled by chiefly by hormones vitamin D and PTH. Vitamin D enters circulation via synthesis in the skin or intestinal absorption and is subsequently converted to its active form, 1,25(OH)2D via separate hydroxylation processes in the liver and kidneys. Both 25(OH)D and 1,25(OH)2D are regulated by classical negative feedback. PTH acts to increase serum calcium by increasing active vitamin D and stimulating bone remodeling. It is regulated primarily by serum calcium with some contribution from circulating vitamin D levels. #Pathophysiology #Endocrinology #Calcium #Homeostasis #PTH #VitaminD
