Calcium-sensing receptor and apoptosis in parathyroid hyperplasia of patients with secondary hyperparathyroidism

Abstract

Objective This retrospective study investigated the characteristics of secondary hyperparathyroidism (SHPT) by examining the presence of the calcium-sensing receptor (CaSR) and the rate of cell proliferation and apoptosis in parathyroid glands. Methods Eighteen diffuse and 57 nodular hyperplastic parathyroid glands from 24 patients with SHPT were compared with 14 primary adenomas and 33 normal parathyroid glands using immunohistochemical staining of CaSR and a marker of proliferative activity (Ki67 antigen). Apoptosis was measured using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling assay. Results The mean ± SE labelling index (LI) of CaSR (12.8% ± 1.5%) in nodular hyperplasia was significantly lower than that in normal parathyroid glands (26.8% ± 0.8%), whereas the mean ± SE LI of CaSR in diffuse hyperplasia was similar to that in normal parathyroid glands (23.3% ± 1.8%). The mean ± SE LI of Ki67 antigen was significantly higher in primary adenoma and nodular hyperplasia than in normal parathyroid glands. Conclusion These results indicate that downregulation of CaSR, and a higher rate of proliferation over apoptosis, could contribute to the pathological progression of SHPT.