Parathyroid function in persistent hyperparathyroidism: Relationship to gland size

Parathyroid function in persistent hyperparathyroidism: Relationship to gland size. The release of parathyroid hormone in experimental animals is related inversely to the plasma calcium concentration. The relevance, though, of these observations to the dynamics of parathyroid function in normal and hyperparathyroid humans is uncertain. We assessed the in vivo parathyroid hormone response to changes in extracellular calcium in 8 normal subjects and 15 patients with persistent hyperparathyroidism following renal transplantation. In 12 hyperparathyroid patients, the hormone response was related to their total gland size measured at the time of their parathyroidectomy. Plasmaionized calcium, magnesium, and parathyroid hormone concentrations were measured in the basal state and during a 2-hr infusion of EDTA (50 mg/kg), and a 4-hr calcium infusion (15 mg/kg). The parathyroid function curves of both groups of subjects (P < 0.001) fit a log-linear relationship. The slopes of the respective parathyroid function curves were similar, although the hyperparathyroid curve was shifted to the right (P < 0.0001). Gland size was not predicted by basal PTH levels; however, it did correlate with changes in parathyroid hormone induced by EDTA (P < 0.001) and calcium (P