Endocrine Abstracts

Background: QT interval reflects cardiac ventricular repolarization and, if prolonged, increases the risk of malignant arrhythmias such as torsade de pointes. QT interval duration is similar in boys and girls during childhood but shortens in males after puberty. In fact, reference limits for QTc in adults reflect this difference, i.e. lower than 460 ms in women and lower than 440 ms in men. Experimental studies suggest that testosterone is the major contributor to shortening of QT interval in men. Purpose of this study is to evaluate the length of ventricular repolarization in male hypogonadal patients.

Methods: The study was performed in 32 patients with secondary (25 patients) and primary hypogonadism (7 patients with Klinefelter’s syndrome) and 32 age-matched eugonadal men. Patients were tested in basal conditions and after adequate testosterone replacement therapy. Twelve-lead ECG recordings were obtained and QT intervals corrected for heart rate according to Bazzett’s formula, i.e. QTc=QT/√RR interval.

Results: Prevalence of abnormal QTc was significantly higher in hypogonadal patients (16% vs 0% in controls, P<0.05). QTc interval normalized on hormone replacement therapy in patients presenting prolonged measurements in the hypogonadal state. Heart rate and left ventricular mass did not differ among the two groups and no known QT-prolonging factor was evidenced in patients with abnormal QTc values.

Conclusions: Testosterone deprivation leads to an increased prevalence of prolonged QTc interval and hypogonadal men appear at higher risk for cardiac arrhythmias. This study reveals an additional feature of male hypogonadism which should be corrected by testosterone replacement therapy.