Involvement of α-klotho, fibroblast growth factor-, vitamin-D- and calcium-sensing receptor in 53 patients with primary hyperparathyroidism

The presentation of patients with primary hyperparathyroidism is often atypical and ranges from normocalcemic, primary hyperparathyroidism to severe, symptomatic hypercalcemia. G-protein-coupled, calcium-sensing receptor (CaSR), vitamin D receptor (VDR), and fibroblast growth factor receptor (FGFR)/klotho complexes seem to be involved in the development of pHPT. Parathyroid glands from 53 patients with pHPT and normal parathyroid tissue from 7 patients were obtained during parathyroidectomy. Conventional detailed morphological and immunohistochemical analyses of parathyroid glands were performed after dividing each slide in a 3 × 3 array. From morphology, the number of lipocytes was significantly lower in parathyroid tissue glands in the pHPT group (p < 0.001). Protein expressions of klotho, CaSR, and VDR were significantly reduced in the pHPT compared with the control group (p = 0.004, p = 0.007, p < 0.001). No differences were seen between the two groups (p = 0.35) regarding expression of FGFR. Correlations between expression showed significant positively correlations between klotho and CaSR and FGFR and VDR. No correlations between klotho expression and serum calcium levels could be detected (R = −0.13, p = 0.66), but there were positive correlations between expressions of CaSR/serum phosphate and klotho/serum phosphate. Impaired protein expression of CaSR and VDR seem to be involved in the development of pHPT. The role of the FGFR/klotho-axis remains still unclear. Correlations between protein expression of CaSR and serum phosphate and klotho and serum phosphate levels could be detected. Whether these findings give new insights into the pathogenesis of the disease is yet unknown and has to be elucidated.