[Hypercalcemia is the most common manifestation of hyperparathyroidism]

Hypercalcemia accompanying with the elevation of parathyroid hormone (PTH) is critical for the differentiation of primary hyperparathyroidism (I HPT) from other diseases which show hypercalcemia. Recently, the reliable immunoassays for PTH especially for intact-PTH have been established and widely introduced in the clinical field. Marked development of cellular and molecular biology also contribute to the exploration of the mechanism of calcium/bone metabolism. The diagnosis of I HPT can be easily established in some patients by their typical clinical findings. Many of them, however, usually show asymptomatic hypercalcemia while some patients show normocalcemia. It is highly important to evaluate the parathyroid function precisely by several biochemical or hormonal parameters related to calcium metabolism for complete diagnosis and treatment.