Testosterone
Also called TRT; testosterone cypionate, enanthate, gels and creams
The main male sex hormone. Testosterone replacement therapy (TRT) is FDA approved for men with low testosterone caused by a medical condition, confirmed by blood tests.
Overview
What it is
A steroid hormone, not a peptide. Prescription forms include weekly or every-other-week injections (cypionate, enanthate), daily gels and creams, patches, nasal gel, oral capsules and implanted pellets.
How it works
Replacing testosterone raises blood levels back to the normal range, which can improve libido, energy, mood, muscle and bone density in men who are truly deficient. Because the brain senses the outside testosterone, it lowers LH and FSH, which shuts down the testicles' own testosterone and sperm production.
What the research shows
Endocrine Society guidelines recommend diagnosing low testosterone only with symptoms plus at least two early-morning blood tests showing low levels. The Testosterone Trials found modest improvements in sexual function, mood and walking in older men with low levels. The TRAVERSE trial (2023) found testosterone did not increase major heart events compared with placebo in men at high cardiovascular risk, but atrial fibrillation, acute kidney injury and blood clots in the lungs were more common. The cypionate label range is 50 to 400 mg every 2 to 4 weeks; providers adjust to blood levels.
Studied for
- Male hypogonadism, low testosterone from a medical causeFDA approved
- Sexual function, mood and energy in older men with low levelsTestosterone Trials
- Bone density and anemia in men with low levels
Safety and regulatory status
Safety and side effects
Raises red blood cell count (hematocrit), which needs monitoring, and can raise blood pressure and worsen sleep apnea. Shrinks the testicles and lowers sperm count, so it is not for men trying to conceive. Gels and creams can transfer to women and children by skin contact. Not for men with prostate or breast cancer. Needs blood tests before starting and during treatment.
Regulatory status
FDA approved prescription medicine and a Schedule III controlled substance. Not approved for age-related low testosterone without a medical cause.
Common questions
Will TRT affect fertility?
Yes. It usually lowers sperm count, sometimes to zero. Men who want children are often offered options such as enclomiphene or hCG instead.
What labs are checked?
Testosterone (morning), hematocrit and, for many men, PSA, before starting and periodically during treatment.
Related in Hormones and Reproductive Health
Sources and further reading (4)
- Testosterone cypionate injection, FDA prescribing information.
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab, 2018.
- Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy (TRAVERSE). N Engl J Med, 2023.
- Snyder PJ, et al. Effects of testosterone treatment in older men (Testosterone Trials). N Engl J Med, 2016.