Over the last 15 years there has been growing recognition of the benefits of testosterone supplementation therapy (TST) for men with testosterone deficiency (TD), also termed hypogonadism.These benefits include improved sexual interest and performance, improved mood,energy, increased muscle and bone density, decreased fat,and possibly improved longevity.The new interest in TST has precipitated re-examination of traditional assumptions regarding the relationship between testosterone (T) and prostate cancer (Pca), leading to a fundamental paradigm shift.This shift is at odds with longstanding beliefs, and has resulted in controversial new practices, such as offering TST to men with Pca.