Compound profile
Testosterone
Also known as Testosterone cypionate (Depo-Testosterone), Testosterone enanthate (Xyosted), Testosterone undecanoate (Aveed, Jatenzo), Testosterone propionate, AndroGel, TRT, Test
Last reviewed October 2026
Educational only. A summary of published research, not medical advice or a recommendation. No doses are listed.
Quick take
The main male sex hormone. Prescribed as testosterone replacement therapy (TRT) for diagnosed low testosterone, and the most widely used anabolic steroid outside medicine.
- Class
- Anabolic steroids
- Status
- FDA-approved
- Evidence
- Large human trials
- Half-life
- Depends on the ester: about 8 days for cypionate (per its label), roughly 4–5 days for enanthate
Mechanism fingerprint
What it acts on, and how. Each chip links to that pathway on the map.
Binds the androgen receptor to build muscle and drive male traits. Some is converted to estradiol (by aromatase) and to DHT (by 5α-reductase), which explains several side effects. An attached ester (cypionate, enanthate, propionate) slows its release from the injection site.
What makes it different
The body's own male hormone and the reference point for the other steroids here: it's the one prescribed as replacement therapy, and it converts to both estradiol and DHT.
Compare side by side
Mechanism & pathways
-
Agonist
Androgen receptor
Receptor for testosterone and DHT. Activating it builds muscle and drives male traits such as body hair and a deeper voice. Every anabolic steroid binds it.
-
Converted by
Aromatase
converts some to estradiol
An enzyme that converts testosterone, and some other steroids, into estrogens such as estradiol. Steroids it works on can cause estrogen-related effects such as water retention and breast tissue growth.
-
Converted by
5α-reductase
converts some to DHT
An enzyme that converts testosterone into DHT, a stronger androgen, in skin, scalp and prostate. It turns nandrolone into a weaker androgen instead.
Evidence overview
Large human trials
Studied extensively in men with hypogonadism, including the T Trials and the TRAVERSE trial, which found no increase in major heart events at replacement doses in men at higher heart risk. Doses above replacement are far less studied.
A breakdown into human, animal and cell studies hasn't been added for this compound yet.
Why it's used
Medically, it restores normal levels in men with diagnosed low testosterone, improving sex drive, energy, bone density and muscle mass. Outside medicine, it's the base of most steroid use, for muscle and strength.
Prescribed testosterone replacement (TRT)
For men with confirmed low testosterone, the Endocrine Society guideline lists testosterone cypionate or enanthate at 75–100 mg a week, or 150–200 mg every 2 weeks, by injection. Gels, patches, pellets and oral testosterone undecanoate are alternatives. The dose is adjusted to keep blood levels in the mid-normal range, with testosterone and hematocrit checked before starting and during treatment.
Only under a prescriber's care, with bloodwork. Source: Bhasin S et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018.
Side effects & risks
Reported side effects
- Acne and oily skin
- Higher red blood cell count (hematocrit)
- Breast tissue growth (gynecomastia) from conversion to estradiol
- Fluid retention
- Testicular shrinkage and lower sperm count
- Hair loss in people prone to male-pattern baldness
Risks and warnings
- Thicker blood from a high hematocrit raises clot and stroke risk, which is why it's monitored on TRT
- Lowers sperm production, so testosterone therapy isn't used in men trying to conceive
- In the TRAVERSE trial, more atrial fibrillation, acute kidney injury and pulmonary embolism than with placebo
- Above replacement levels: higher blood pressure, worse cholesterol and a higher risk of heart muscle damage
- Can worsen untreated sleep apnea
- Gels carry a boxed warning: skin contact can pass testosterone to children and women
- In women: masculinizing effects (deeper voice, facial and body hair, clitoral enlargement) that can be permanent.
- Schedule III controlled substance in the US: illegal to possess without a prescription.
- Prohibited in sport by the World Anti-Doping Agency (WADA).
FAQ
Short answers taken from this profile.
What is Testosterone?
The main male sex hormone. Prescribed as testosterone replacement therapy (TRT) for diagnosed low testosterone, and the most widely used anabolic steroid outside medicine.
How does Testosterone work?
Binds the androgen receptor to build muscle and drive male traits. Some is converted to estradiol (by aromatase) and to DHT (by 5α-reductase), which explains several side effects. An attached ester (cypionate, enanthate, propionate) slows its release from the injection site.
What receptors or pathways does Testosterone act on?
androgen receptor (agonist), aromatase (converted by; converts some to estradiol) and 5α-reductase (converted by; converts some to DHT).
How is Testosterone different from similar compounds?
The body's own male hormone and the reference point for the other steroids here: it's the one prescribed as replacement therapy, and it converts to both estradiol and DHT.
What is the half-life of Testosterone?
Depends on the ester: about 8 days for cypionate (per its label), roughly 4–5 days for enanthate.
Is Testosterone approved?
FDA-approved for men with low testosterone caused by a diagnosed medical condition (hypogonadism). Not approved for age-related decline alone, or for performance or bodybuilding.
What has Testosterone been studied for?
Medically, it restores normal levels in men with diagnosed low testosterone, improving sex drive, energy, bone density and muscle mass. Outside medicine, it's the base of most steroid use, for muscle and strength.
How strong is the evidence?
Large human trials. Studied extensively in men with hypogonadism, including the T Trials and the TRAVERSE trial, which found no increase in major heart events at replacement doses in men at higher heart risk. Doses above replacement are far less studied.
What are the main risks?
Thicker blood from a high hematocrit raises clot and stroke risk, which is why it's monitored on TRT. Lowers sperm production, so testosterone therapy isn't used in men trying to conceive. In the TRAVERSE trial, more atrial fibrillation, acute kidney injury and pulmonary embolism than with placebo. More are listed under risks and warnings.
Sources
- 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. N Engl J Med 2023 (TRAVERSE).
- FDA prescribing information for Depo-Testosterone and AndroGel.
- Pope HG et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev 2014.