PTH, also known as parathormone, is made by the parathyroid glands. PTH is directly involved in the functioning of bones, kidneys, and the small intestine.
In the bones, PTH stimulates the release of calcium in an indirect process through osteoclasts which ultimately leads to resorption of the bones.
Parathyroid hormone regulates calcium levels in the blood, largely by increasing the levels when they are too low.
In the kidney, parathyroid hormone blocks the reabsorption of phosphate in the proximal tubule while promoting calcium reabsorption in the ascending loop of Henle, distal tubule, and collecting tubule.
PTH indirectly increases calcium absorption from food in the intestine, via its effects on vitamin D metabolism.
PTH has no effect on carbohydrate metabolism.