Parathyroid hormone release in vitro in hyperparathyroidism associated with multiple endocrine neoplasia type 1.

Hyperparathyroidism (HPT) in the syndrome of multiple endocrine neoplasia type 1 (MEN-1) exhibits a different picture regarding its propensity for recurrence compared with sporadic primary HPT. In order to shed further light on the MEN-1 syndrome an investigation in vitro was made of parathyroid hormone (PTH) release of dispersed parathyroid cell from 11 patients with parathyroid hyperplasia associated with MEN-1, 10 patients with single parathyroid adenomas, and 10 preparations of normal bovine parathyroid glands. The two patient groups had the same average serum calcium value prior to surgery. Immunoreactive concentrations of PTH were measured after 2-h incubations at extracellular calcium concentrations of 0.5-3.0 mmol/l. Compared with the normal bovine parathyroid cells, the cells of the MEN-1 patients had a reduced calcium sensitivity of the PTH release and secreted smaller amounts of hormone at both low and high extracellular calcium concentrations. A similar abnormality of the PTH release was found for the cells of the hyperplastic and adenomatous parathyroid glands. Although individual parathyroid glands were investigated in only three MEN-1 patients, the results suggested the secretory regulation to be less defective in the small glands of each patient. It is concluded that in patient groups matched for serum calcium, the parathyroid tissue of MEN-1 patients has an abnormality of the PTH release similar to that of parathyroid adenomas.