The presence of elevated parathyroid hormone on the parathyroid hormone panel suggests that hyperparathyroidism may be occurring; a decrease suggests hypoparathyroidism. If necessary, the results of other tests should be combined. Parathyroid hormone, also known as PTH, is an alkaline, single-chain polypeptide hormone secreted by the main parathyroid cells. The interaction of PTH and calcitonin maintains the stability of blood calcium levels. Elevated blood calcium inhibits PTH secretion, while lowered blood calcium promotes PTH secretion. Altered PTH secretion caused by parathyroid dysfunction leads to elevated or lowered blood calcium levels (hypercalcemia or hypocalcemia). Abnormalities in serum parathyroid hormone are recommended for hospitalization.