Primary Hyperparathyroidism : A Study of Cardiovascular Dysfunction and its Reversibility After Parathyroidectomy

Abstract: Cardiovascular risk in primary hyperparathyroidism (HPT) is controversial, and studies mainly from Europe associate HPT with increased cardiovascular morbidity and mortality. Cardiovascular morphology and function were evaluated prospectively in 31 consecutive HPT patients (mean serum calcium 2.97±0.04) and randomly enrolled controls matched for age and sex. Patients were re-examined at normocalcemia about one year after parathyroidectomy. HPT patients showed an operatively reversible disturbance in endothelial vasodilatory function that seemed unrelated to an early sign of atherosclerosis, i.e. thickness of carotid artery intima-media complex. Acute hypercalcemia in healthy subjects induced a similar impairment in endothelial function, which suggests a dependence on biochemical rather than structural vascular changes in HPT. Echocardiography showed left ventricular diastolic dysfunction and supernormal systolic performance being reversed after operation. Left ventricular mass tended to be irreversibly increased. During exercise HPT patients exhibited greater rise in systolic blood pressure compared to controls and an increased number of premature ventricular beats. This indicated increased work load and a propensity for fatal cardiac events. Following surgery, an improvement with less pronounced ST-segment depression was seen. 24-hour ambulatory blood pressure monitoring showed irreversibly increased levels despite maintained diurnal rhythm, while 24-hour heart rate variability analysis displayed blunted nocturnal increase of low and very low frequency bands that was corrected postoperatively. Parathyroidectomy seems to alleviate most of the cardiovascular disturbances in HPT, except for hypertension. This is consistent with the normalised longevity in HPT treated with parathyroidectomy and supports active treatment of HPT.