Parathyroid Hormone Secretion from Dispersed Human Hyperparathyroid Cells: Increased Secretion in Cells from Hyperplastic Glands versus Adenomas*

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Abstract
The in vitro secretion of PTH by dispersed human parathyroid cells was examined under conditions of low and high extracellular Ca†2 using tissue from patients with primary hyperparathyroidism and hyperparathyroidism resulting from chronic renal failure (CRF). The PTH secretion rate (nanograms of PTH per 105 cells/h) was lower in adenomatous tissues than in either primary hyperplastic cells or CRF cells under conditions of low (0.5 mM) or high (2.0–3.0 mM) extracellular Ca†2. Among the adenomas, a wide spectrum of degree of suppressibility of PTH secretion by high Ca†2 was found, ranging from 0% (completely nonsuppressible) to 98%. Suppression of the hyperplastic tissues in general was similar. The most suppressible adenomas demonstrated 2-fold greater PTH secretion rates in low Ca†2 conditions than the least suppressible adenomas, but in high Ca†2 conditions, the two groups had similar secretory rates. We conclude that the rate of PTH secretion by cells from adenomas was substantially lower than that of cells from tissues exhibiting either primary hyperplasia or hyperplasia resulting from CRF under these in vitro conditions. Thus, in adenomas, an increase in absolute cell number as well as alterations in the degree of calcium responsiveness may prove to be important etiological factors in the expression of hyperparathyroidism.