With this background, it seems logical to speculate that androgens may play a role in the modulation of cardiac repolarization. Patients of both sexes exhibiting abnormal plasma levels of testosterone may serve as a useful clinical model for investigating this question. We therefore analyzed cardiac repolarization in men with androgen deprivation and compared these data with those of women exhibiting a virilization syndrome. Methods Study population ECG analysis of cardiac repolarization was carried out in a study population totaling 106 patients distributed into 2 groups. The first group of 53 patients exhibiting abnormal levels of testosterone was referred to us from the divisions of urology and endocrinology for routine cardiovascular examination. This group included 25 men with androgen deprivation as a therapy for prostate carcinoma and 2 men with a traumatic ablation of the testes (only patients with plasma levels of androstenediolone below 2.88 mg/mL or bioavailable testosterone below 0.00 to 0.45 nmol/L were included in the study). Twenty-six women with a virilization syndrome (hyperplasia of the adrenal cortex in 4 patients and polycystic ovarian disease in 22 patients, with plasma level of androstenediolone of 5.6 ± 1.4 mg/mL for a nor- mal value of 2.88 mg/mL or bioavailable testosterone of 0.74 ± 0.14 nmol/L for a normal range between 0.00 and 0.45 nmol/L) were also included in this group. The control group included 53 normal subjects pair-matched for age and sex. These patients had a normal history and physi- cal examination, were not taking cardioactive medication, and had normal ECG recordings. Sex has been considered for many years as a factor that may influence the electrocardiographic (ECG) pattern of cardiac repolarization. A longer duration of repolarization, reflected by a longer QT interval, and a low T-wave amplitude are present in the surface ECG of women as opposed to men. 1,2 Also, it has been reported that, whereas in both men and women the descending limb of the T wave is steeper than the ascending limb, the maximum slope of each limb is steeper in men than in women. 3 Moreover, it is now understood that women are more susceptible to the development of torsades de pointes in various settings of QT prolongation. 4,5 How- ever, it remains unclear whether such relative sex dif- ferences in adults reflect an intrinsically longer duration of repolarization in women or whether it means an actual shortening of repolarization in men. 6 On the other hand, the lack of significant effects of hormone replacement therapy on QT interval in postmenopausal women 7 or the absence of differences in QT interval duration during the menstrual cycle 8 argue against a contributory role of estrogen or progesterone to account for the sex differences in myocardial repolarization. From the a Facultad de Medicina, Universidad del Salvador; b Facultad de Medicina, Universidad Nacional de la Plata; and the c Laboratorio de Electrofisiología Cardíaca, Universidad Favaloro. Submitted April 18, 2000; accepted June 27, 2000. Reprint requests: Ricardo A. Quinteiro, MD, PhD, Solis 453, 4th Floor, Buenos Aires 1078, Argentina. Copyright © 2000 by Mosby, Inc. 0002-8703/2000/$12.00 + 0 4/1/109918 doi:10.1067/mhj.2000.109918 Sex differences on the electrocardiographic pattern of cardiac repolarization: Possible role of testosterone Héctor Bidoggia, MD, a Juan P. Maciel, MD, a Norberto Capalozza, MD, a Susana Mosca, MD, b Enrique J. Blaksley, BSc, a Esteban Valverde, EEng, c Guillermo Bertran, BSc, c Pedro Arini, EEng, c Marcelo O. Biagetti, BSc, c and Ricardo A. Quinteiro, MD,PhD c Buenos Aires, Argentina Background Cardiac repolarization has been shown to be shorter and faster in men compared with women. In this study, we examined the electrocardiographic pattern of repolarization in patients with abnormal plasma levels of testosterone to gain insight into the role that this hormone plays in modulating repolarization. Methods and Results Repolarization was measured in 27 castrated men, 26 women with virilization, and 53 control subjects pair-matched for age and sex. Repolarization in castrated men was slower and longer than that of normal men. Women with virilization exhibited a shorter and faster repolarization than normal women and castrated men. These differences are the opposite of those found in the normal population. Finally, the changes observed in castrated men may be reverted by testosterone. Conclusions We conclude that testosterone plays an important role in modulating cardiac repolarization. (Am Heart J 2000;140:678-83.)