parathormone

Increases plasma calcium levels. It increases resorption of calcium from bone, and when present continuously at high concentrations, it increases the number of bone remodeling units and activates osteoclasts. It increases calcium reabsorption in the distal renal tubule and promotes phosphate excretion. PTH also enhances the formation of calcitriol in the kidney by activating 1α-hydroxylase, which then promotes intestinal calcium absorption. PTH receptors are G protein coupled, increasing cAMP and intracellular Ca2+.