Augmentation of central arterial pressure in mild primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is associated with increased cardiovascular risk, although the mechanisms involved remain unclear. Recent evidence has shown increased pulse pressure to be a powerful predictor of cardiovascular events. As increases in pulse pressure are due largely to arterial stiffening, we measured arterial stiffness in 21 subjects with PHPT (18 women and 3 men; 46-71 yr old) and 21 age- and sex-matched healthy controls using pulse wave analysis, a technique that measures peripheral arterial pressure waveforms and generates corresponding central aortic waveforms. This allows determination of the augmentation of central pressure resulting from wave reflection and augmentation index, a measure of vessel stiffness. Metabolic parameters were also measured. The serum calcium level among PHPT subjects was (mean ± SD) 2.74 ± 0.14 mmol/L. pulse wave analysis showed that both augmentation and the augmentation index were significantly higher in the PHPT group vs. controls [16 ± 5 vs. 10 ± 4 mm Hg (P < 0.001) and 36 ± 9% vs. 25 ± 6% (P < 0.001)] despite comparable brachial systolic pressures between groups (136 ± 13 vs. 134 ± 18 mm Hg). Patients with PHPT had higher fasting serum insulin levels [median (range), 15.8 (7.4-39.4) vs. 11.6 (5.1-23) mU/L; P < 0.05] and triglyceride (1.6 ± 0.6 vs. 1.2 ± 0.4 mmol/L; P < 0.05), but lower high density lipoprotein cholesterol (1.4 ± 0.4 vs, 1.6 ± 0.3 mmol/L; P < 0.05). These data indicate that subjects with mild PHPT (calcium, <3.0 mmol/L) have increased arterial stiffness, as evidenced by higher augmentation of central aortic pressures. Enhanced vessel stiffness may arise from a combination of structural and functional vascular changes due to hypercalcemia and/or metabolic abnormalities. Increased vascular stiffness in subjects with PHPT may account in part for the increased cardiovascular risk in this group.