Is primary hyperparathyroidism a cause of endothelial dysfunction?

Symptomatic primary hyperparathyroidism (PHPT) is thought to be related to increased cardiovascular morbidity and mortality. In our study, we aimed to investigate endothelial dysfunction and markers of subclinical atherosclerosis in patients with PHPT. Also we aimed to demonstrate the effect of vitamin D supplementation on these parameters.

Twenty-nine patients followed by medical treatment (A), 25 preoperative (B) and 23 postoperative patients with PHPT (C), and 26 normocalcaemic subjects (D) were included. Groups were assessed by measurements of flow-mediated dilation (FMD), carotid intima-media thickness (CIMT), serum levels of sCD40L, high-sensitivity CRP (hs-CRP) and interleukin-8 (IL-8). Thirteen patients with low levels of 25-hydroxy-vitamin D (25OHD) in the medical treatment group were assessed before and 3 months after vitamin D replacement.

The median FMD was 5% in group A, 5.1% in group B, 7.6% in group C and 7.7% in group D. The FMD measurement in group A was significantly lower than groups C and D (P=.02) and was similar to the FMD measurement in group B. FMD measurements of group B were not significantly lower than groups C and D. In 13 patients with low 25OHD in group A, the median FMD increased to 7.07% from 4.71% after vitamin D replacement (P=.02).

Flow-mediated dilation was impaired in patients with PHPT, particularly in the medically observed group. Vitamin D supplementation seems to provide improvements in FMD in medically observed PHPT patients with low 25OHD levels, and this was the novel observation of our study.