Serum parathyroid hormone (PTH) concentrations in hypercalcemia and hypocalcemia

Serum PTH concentrations according to the serum total calcium concentration in various disease states. The normal range is shown in the white box. The sigmoidal curve (green stars) is derived from a calcium citrate infusion protocol administered to 38 normal subjects. Serum PTH and calcium values are low in hypoparathyroidism (open blue boxes) and high in primary hyperparathyroidism (blue squares). The serum calcium concentration is high and serum PTH is appropriately low in patients with non-PTH-induced hypercalcemia of malignancy (red circles).