DEPRESSED EXPRESSION OF CALCIUM RECEPTOR IN PARATHYROID-GLAND TISSUE OF PATIENTS WITH HYPERPARATHYROIDISM

The factors involved in abnormal parathyroid cell secretory function a nd growth in patients with primary (I degrees) and secondary (II degre es) hyperparathyroidism are still incompletely understood. We compared the expression of the calcium-sensing receptor (CaR) at the gene mess age and the protein level in parathyroid tissue obtained from patients with I degrees non-uremic or II degrees uremic hyperparathyroidism wi th that in normal parathyroid tissue, using in situ hybridization and immunohistochemistry techniques. The expression of the CaR mRNA and pr otein was reduced in most cases of I degrees adenoma and II degrees hy perplasia, compared with strong expression in normal parathyroid tissu e. In II degrees hyperparathyroidism, expression of both receptor mRNA message and protein was often particularly depressed in nodular areas , compared with adjacent non-nodular hyperplasia. Decreased Ca-R expre ssion in adenomatous and hyperplastic parathyroid glands would be comp atible with a less efficient control of PTH synthesis and secretion by plasma calcium than in normal parathyroid tissue.