125 Characteristics of Testicular Atrophy During Testosterone Replacement Therapy (TRT)

ABSTRACT Objectives Testosterone replacement therapy (TRT) is a common treatment for late-onset hypogonadism. In addition to adverse events such as polycythemia, it is reported that TRT may cause testicular atrophy due to decreased gonadotropin; however, there are no reported studies that have actually observed the degree of atrophy. We investigated changes in testicular size in patients undergoing TRT and examined the characteristics of testicular atrophy. Subjects and Methods Testicular size was measured before treatment and at 3 months, 6 months, and every 6 months after treatment up to 24 months in 121 patients undergoing TRT for more than 3 months. The size of each testicle was measured using a punched-out elliptical ring orchidometer, and the average testicular volume was calculated. Patients showing testicular atrophy at 3 months after the start of TRT were classified as the atrophy group, and cases with no change were classified as the unchanged group. Results The age of the subjects ranged from 38 to 81 (mean 53.7 years). Overall, testicular volume decreased over time, from a mean of 16.5 ml before treatment to 13.7 ml at 24 months, with atrophy becoming significant from 6 months. In the atrophy group (60 cases), the atrophic tendency persisted after 6 months, whereas in the unchanged group, no atrophic tendency was seen after 24 months. The background factors of the two groups were compared. Among age, baseline testicular volume, testosterone, and method of TRT administration (injection or ointment), the items that showed significant differences between the two groups were baseline testicular volume and method of administration. Testicular atrophy was more likely to occur in patients with larger baseline testicular size or those treated with injectable formulations. Conclusion For patients with large testicular volume or anxiety about testicular atrophy, it may be better to recommend TRT in ointment form rather than injectable formulations. Disclosure Work supported by industry: no.