Endocrine Abstracts

Introduction: Primary hyperparathyroidism (pHPT) is the unregulated overproduction of parathyroid hormone resulting in abnormal calcium homeostasis. The prevalence has been reported to be ~21 cases/100 000 person-years. The mean age at diagnosis has remained between 52 and 56 years with female-to-male ratio 3:1. In ~85% of cases, pHPT is caused by a single adenoma, in 14% of hyperplasia and 1% is caused by malignant diseases. Association between pHPT and cardiovascular manifestation is well known for many years. Increased cardiovascular mortality rates were reported in many studies. Changes in serum calcium level have impact on duration of QT interval. QT interval duration was inversely associated with the serum total and ionized calcium. Data from the Third National Health and Nutrition Examination Survey suggests that shortened and prolonged QT – interval durations, even within a reference range, are associated with increased mortality risk in the general population.

Methods: Aim of our study was to compare ECG changes especially QT and RR interval using 24 h ambulatory electrocardiography in patients with pHPT and controls. A total of 41 (39 women and two men) patients with pHPT and 41 control subjects of similar age, body weight and cardiovascular risk factors was enrolled in this study. The age of participants ranged from 28 to 83 years (mean age was 55 years), the serum calcium level was from 2.62–3.06 mmol/l (reference range (RR) 2.25–2,65 mmol/l), the level of an intact parathormone was between 61.4 and 441 ng/ml (RR 65 ng/ml). A control group consisting of 41 patients (40 women and one men), the age of control group ranged from 40–75 years (mean age was 57.5 years), the serum calcium level was in the reference range from 2.25 to 2.55 mmol/l, the level of the intact parathormone was from 48.01 to 60.5 ng/ml.

Results: We observed statistically significant data - changes in QT interval and RR interval as follows: QT max. (886.122 vs 749.317; P 0.0013; median 850 vs 773; P<0.001), QTc max. (992.122 vs 806; P<0.001; median 910 vs 781; P 0.004), QTc min. (89.5366 vs 100.854; P<0.002; median 90 vs 104; P 0.0015), RR average (754.658 vs 794.366; P 0.0133), RR max. (4573.41 vs 2418.37; P<0.0113; median 1445 vs 1063; P 0.0004), and RR min. (351.902 vs 470.268; P 0.0003).

Conclusion: There are resulting data about a statistic impact of hypercalcaemia in primary hyperparathyroidism at QT max., QTc max. and QTc min., and all RR intervals (RR min., RR aver, and RR max.). In accordance with published data we confirm a statistic significance shortening of QT interval, especially QTc min. interval in patients with pHPT, but conflicting data about impact of hypercalcaemia at QTc max. and QT max. interval, there we observed prolonged QT intervals in patients with pHPT compared with controll group. RR average and RR min. intervals were shorter in observed group compared to controlls. Changes in QT interval (shortening or prolongation) are associated with higher cardiovascular or total mortality in general population.