Parathyroid hormone, also called parathormone or parathyrin, is a hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney, and intestine. PTH is made by four tiny parathyroid glands in your neck. A parathyroid hormone (PTH) test is a blood test that measures the amount of PTH in your blood. Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of blood calcium levels. PTH, also known as parathormone, is made by your parathyroid glands. Parathyroid Hormone (PTH) · PTH directly promotes the release of calcium from bones into the bloodstream.