Background: Testosterone treatment rates in adult men have increased in the United States over the past 2 decades.
Purpose: To assess the benefits and harms of testosterone treatment for men without underlying organic causes of hypogonadism.
Data sources: English-language searches of multiple electronic databases (January 1980 to May 2019) and reference lists from systematic reviews.
Study selection: 38 randomized controlled trials (RCTs) of at least 6 months' duration that evaluated transdermal or intramuscular testosterone therapies versus placebo or no treatment and reported prespecified patient-centered outcomes, as well as 20 long-term observational studies, U.S. Food and Drug Administration review data, and product labels that reported harms information.
Data extraction: Data extraction by a single investigator was confirmed by a second, 2 investigators assessed risk of bias, and evidence certainty was determined by consensus.
Data synthesis: Studies enrolled mostly older men who varied in age, symptoms, and testosterone eligibility criteria. Testosterone therapy improved sexual functioning and quality of life in men with low testosterone levels, although effect sizes were small (low- to moderate-certainty evidence). Testosterone therapy had little to no effect on physical functioning, depressive symptoms, energy and vitality, or cognition. Harms evidence reported in trials was judged to be insufficient or of low certainty for most harm outcomes. No trials were powered to assess cardiovascular events or prostate cancer, and trials often excluded men at increased risk for these conditions. Observational studies were limited by confounding by indication and contraindication.
Limitation: Few trials exceeded a 1-year duration, minimum important outcome differences were often not established or reported, RCTs were not powered to assess important harms, few data were available in men aged 18 to 50 years, definitions of low testosterone varied, and study entry criteria varied.
Conclusion: In older men with low testosterone levels without well-established medical conditions known to cause hypogonadism, testosterone therapy may provide small improvements in sexual functioning and quality of life but little to no benefit for other common symptoms of aging. Long-term efficacy and safety are unknown.
Primary funding source: American College of Physicians. (PROSPERO: CRD42018096585).