Effects of parathyroid hormone and serum calcium on the phenotype and function of mononuclear cells in patients with primary hyperparathyroidism

Background Several studies have demonstrated specific influence of parathyroid hormone (PTH) on immune parameters, especially on T- and B-cell function, migration of polymorphonuclear leucocytes (PMNLs) and antibody synthesis, in patients with secondary hyperparathyroidism and chronic renal failure and recently also in patients with primary hyperparathyroidism (pHPT). Methods We therefore examined 12 patients with pHPT before and 6 months after parathyroidectomy (PTX) and nine sex- and age-matched control subjects to determine the impact of PTH and serum calcium concentrations on several immune parameters, including (a) serum concentrations of immunoglobulins, (b) immunophenotype of peripheral blood lymphocytes, (c) phytohaemagglutinin (PHA)-induced lymphocyte proliferation and (d) monocytic surface marker expression. Results Serum concentrations of immunoglobulins (IgG, IgA, IgM) were unaffected by elevated serum PTH and calcium levels. T lymphocytes (CD3), B lymphocytes (CD19), NK cells (CD16/56) and monocytes (CD16) revealed a normal distribution and were not different before and after PTX in patients with pHPT when compared with the control group. CD4˛ T-helper lymphocytes were significantly elevated pre- and post-operatively in patients with pHPT. The lymphocyte proliferation response to PHA in the highest concentration (12·5 m gL π 1 ) tested was significantly suppressed in patients with pHPT preoperatively when compared with the patients post-operatively and the control group. In addition, both CD4˛ and CD8˛ lymphocytes showed a lower expression of activation markers, interleukin 2 (IL-2) receptor (CD25) and transferrin receptor (CD71), which could be partially restored 6 months after PTX, but did not reach normal values. Conclusion In summary, in contrast to the findings in patients with secondary HPT, pHPT appears to be associated with less alterations of immune functions. Chronically elevated serum PTH and calcium concentrations in patients with pHPT induce a higher percentage of CD4˛ helper T lymphocytes and a suppressed lymphocyte response to PHA as well as a reduced expression of activation markers on peripheral blood lymphocytes.