Anabolic-androgenic steroids (AAS) are synthetic versions of testosterone. They increase muscle protein synthesis and add nuclei to muscle fibres, which is why gains partly persist after stopping. In the only rigorous trial, testosterone with training added roughly 6 kg of fat-free mass in ten weeks versus 2 kg for training alone. Every compound is both anabolic and androgenic; the ratio varies, the separation is never complete.
- Testosterone plus training: about +6 kg fat-free mass and large strength gains in 10 weeks; training alone: about +2 kg (Bhasin et al., NEJM 1996, 43 men).
- Testosterone without any training still added muscle and strength in the same trial. Training roughly doubles the effect.
- Added muscle nuclei persist after use stops, which is the mechanism behind muscle memory.
- Three classes: injectable testosterone esters, oral 17-alpha-alkylated compounds, and structurally modified derivatives with different estrogen conversion and receptor binding.
- Prescription medicines nearly everywhere; controlled substances in the US, UK, EU, Canada and Australia.
What they are
Anabolic-androgenic steroids are synthetic hormones built on testosterone, the main androgen. Men make it in the testes, women in the ovaries and adrenals at about one fifteenth of the amount. Every AAS does two things: builds tissue (anabolic) and promotes masculine traits (androgenic). Both come from the same receptor, so no compound is purely one or the other.
How they build muscle
- The molecule enters the muscle cell, binds the androgen receptor, and changes gene expression: more protein synthesis, less breakdown.
- Over weeks, satellite cells donate new nuclei to muscle fibres. More nuclei, more capacity to grow. These nuclei stay after use stops, which is why regaining is faster than gaining.
- Secondary effects: more red blood cells, altered cortisol handling, more drive in training.
What results to expect
The one controlled trial that matters: Bhasin and colleagues, 1996, 43 healthy men, ten weeks, supraphysiologic testosterone or placebo, with or without supervised lifting.
| Group | Fat-free mass | Bench press 1RM | Squat 1RM |
|---|---|---|---|
| Placebo, no training | ~0 | ~0 | ~0 |
| Testosterone, no training | +3.2 kg | +9 kg | +16 kg |
| Placebo + training | +2.0 kg | +10 kg | +25 kg |
| Testosterone + training | +6.1 kg | +22 kg | +38 kg |
The drug works without training. It works about three times better with it. Everything else on this site follows from that table: the result is the combination, and the stimulus is yours to supply.
The three classes
Injectable testosterone esters. An ester chain slows release; longer ester, less frequent injection, steadier levels. Once the ester is cleaved, it is testosterone. Best studied, easiest to monitor, what physicians prescribe.
Oral 17-alpha-alkylated compounds. A methyl or ethyl group lets the molecule survive the liver, so it works as a tablet. The liver pays: enzyme rises, HDL drops sharply. Short use only, if at all, with liver markers checked.
Modified derivatives. Changes to the skeleton alter receptor binding, whether the compound converts to estrogen via aromatase, and whether it converts to DHT. This is why compounds differ in water retention, hair, skin and mood at similar strength.
Medical use vs sports use
Physicians prescribe testosterone for hypogonadism, delayed puberty, muscle wasting and some anaemias, at doses that restore normal levels, with monitoring. Sports use runs above physiological range, often with several compounds and no monitoring. Nearly all documented harm comes from the second pattern. The gap between the two is not the drug; it is the numbers and the oversight. How to keep the oversight.
Legality
Prescription-only almost everywhere. Controlled substances in the US, UK, Canada, Australia and most of the EU: unlicensed possession or import is a criminal matter. Some countries in Asia and Latin America regulate them as ordinary prescription medicines. Know the law where you live and where you travel.
Frequently asked questions
How much muscle do anabolic steroids add?
The best data: about 6 kg of fat-free mass in 10 weeks with training, versus 2 kg from training alone, at a supraphysiologic testosterone dose in a controlled trial. Individual results vary with training, food, sleep and genetics.
Do the gains stay after you stop?
Partly. Muscle nuclei added during use remain, and strength returns faster when you retrain. Some size is lost as hormone levels fall, less if you keep training hard and eating enough protein through recovery.
Are steroids the same as the ones in asthma inhalers?
No. Those are corticosteroids, related to cortisol, acting on inflammation. Anabolic steroids are related to testosterone and act on muscle, bone and reproductive tissue.
Is testosterone a steroid?
Yes, it is the reference compound every other anabolic steroid is derived from, and the one physicians prescribe most, including for testosterone replacement therapy.
Are anabolic steroids legal?
Prescription-only almost everywhere. In the US, UK, EU, Canada and Australia they are also controlled substances, so unlicensed possession can be a criminal offence. Check your country.
Sources
- Bhasin S et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. NEJM, 1996.
- Kicman AT. Pharmacology of anabolic steroids. British Journal of Pharmacology, 2008.
- Pope HG et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocrine Reviews, 2014.