IMPAIRMENT OF ENDOTHELIUM-INDEPENDENT VASODILATION IN PATIENTS WITH HYPERCALCEMIA

Objective: Patients with primary hyperparathyroidism (PHPT) and/or hyp ercalcemia are at increased risk for myocardial ischemia. Whether PHPT is associated with altered endothelium-dependent dilation, vascular s mooth muscle cell function, or both is unknown. This study was perform ed to test the hypothesis that endothelium-dependent, flow-mediated di lation (FMD) and/or endothelium-independent, nitroglycerin-induced dil ation (NMD) is impaired in the preclinical phase of vascular disease i n patients with PHPT. Methods: Twenty-six PHPT patients (mean +/- SD; age 55 +/- 15y, serum calcium 3.00 +/- 0.37 mmol/l, serum phosphate 0. 79 +/- 0.21 mmol/l, iPTH 249 +/- 262 pg/ml) with no evidence of corona ry artery disease (CAD) as well as 26 normocalcemic control subjects ( CTL; age 51 +/- 12y) were studied. FMD following reactive hyperemia an d NMD after 0.8 mg nitroglycerin (NTG) were assessed in the brachial a rtery by using high resolution ultrasound (7MHz). Results: NMD was imp aired in PHPT patients compared to CTL (11.9 +/- 3.9% vs. 15.6 +/- 5.7 %; p = 0.012). FMD was similar in both study groups (11.6 +/- 4.6% vs. 12.6 +/- 4.9%; NS). The ratio of FMD to NMD was significantly differe nt between PHPT patients and CTL (0.98 +/- 0.19 vs 0.81 +/- 0.25, p = 0.009). On multiple stepwise regression analysis serum calcium was ind ependently associated with the FMD/NMD ratio (r = 0.34, p = 0.017). Co nclusions: Endothelium-independent vasodilation is impaired in PHPT pa tients without clinical evidence of coronary artery disease compared t o normocalcemic CTL, while endothelium-dependent dilation was similar in both study groups. Thus, altered arterial reactivity in the course of PHPT may predominantly involve the arterial media and not the endot helium as observed previously in patients with various stages of ather osclerosis. (C) 1998 Elsevier Science B.V. All rights reserved.