Testosterone Replacement Therapy (TRT)

Overview

Testosterone is the main male sex hormone. Hypogonadism is a condition in which the testes, or the brain signals that control them, do not produce enough of it. Guidelines call for both symptoms and consistently low blood levels, confirmed on repeated morning tests, before a diagnosis is made. Testosterone replacement raises blood levels using injections, gels, patches, pellets or other forms.

What the research has looked at

In men with confirmed hypogonadism, trials have reported improvements in sexual function and in some measures of mood, strength and bone density, with results varying between studies. The TRAVERSE trial followed more than 5,000 men aged 45 to 80 with hypogonadism and either existing heart disease or a higher risk of it. Testosterone gel was not associated with more major cardiovascular events than placebo, but higher rates of atrial fibrillation, acute kidney injury and pulmonary embolism were reported. In 2025 the FDA required label changes for all testosterone products: language about increased cardiovascular risk was removed from the boxed warning, the TRAVERSE results were added, and blood pressure warnings were added because testosterone products raise blood pressure.

Safety and limits

• Testosterone therapy can reduce sperm production and fertility.
• It can raise red blood cell counts and blood pressure, so regular monitoring is part of treatment.
• The approved use is for men with a medical cause of low testosterone, not for age-related decline alone.
• Using testosterone or related drugs without medical supervision, including for muscle building, carries added risks, and these substances are prohibited in sport.

What we do not know

• TRAVERSE tested one product type in one population, and its results do not automatically apply to every man or every formulation.
• Long-term outcomes beyond several years of treatment are less well studied.
• Benefits in men with mild or age-related decline are less certain.

Regulatory context

Testosterone is an FDA-approved prescription medicine for hypogonadism in men and a Schedule III controlled substance in the US. Compounded or online-sourced products are not the same as approved products.

Related pages

See also HRT (Menopausal Hormone Therapy) and the Peptide A-Z.

References & further reading

• Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744.
• Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy. N Engl J Med. 2023;389(2):107-117.

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