Biochemical markers of endothelial activation in primary hyperparathyroidism

Patients with primary hyperparathyroidism (PHPT) have impaired vasodilation both dependent and independent of endothelium. The aims of our study were to measure three different biochemical markers of endothelial activation, i.e., plasma thrombomodulin, soluble(s) E-selectin, and von Willebrand factor, in PHPT patients before and one year after successful parathyroidectomy, and to distinguish the potential effect of hypercalcemia and/or high parathyroid hormone from that of major cardiovascular risk factors (diabetes mellitus, hyperlipidemia, hypertension, obesity, smoking habit) on endothelial function. Twenty consecutive patients with PHPT subdivided into two groups according to the absence (n=8) or presence (n=12) of one or more risk factors, and fifteen healthy normocalcemic subjects were studied. Baseline thrombomodulin levels were similar in the groups with and without risk factors, and in controls. In contrast, sE-selectin and von Willebrand factor were higher in PHPT patients with risk factors than in those without risk factors (p < 0.05 and p < 0.01, respectively) and controls (p < 0.01). Neither thrombomodulin nor sE-selectin changed after parathyroidectomy in either PHPT group. Plasma von Willebrand factor decreased (p < 0.01) in patients without risk factors, while persisting at high levels in patients with risk factors. In conclusion, in spite of a limitation due to the small number of patients, our study suggests that classic cardiovascular risk factors seem to be the main determinants for the high plasma levels of sE-selectin and vWF in PHPT. Together with unaltered thrombomodulin and sE-selectin levels, a plasma vWF decrease after parathyroidectomy might reflect a specific mechanism of its endothelial calcium- and/or PTH-stimulated secretion in some PHPT patients without risk factors. Whether a vWF reduction after parathyroidectomy may be used as a biochemical index for improved endothelial function in PHPT patients without risk factors has yet to be demonstrated in larger studies.