Anabolic steroids are synthetic drugs designed to mimic testosterone, the primary male sex hormone. They fall into a class called anabolic-androgenic steroids (AAS), meaning they have two distinct effects: “anabolic” refers to muscle and tissue building, while “androgenic” refers to the development of male sexual characteristics. In the United States, they are classified as Schedule III controlled substances, placing them in the same legal category as ketamine and certain barbiturates.
How Anabolic Steroids Work in the Body
Once in the bloodstream, anabolic steroids bind to androgen receptors inside cells. This binding changes how genes are read, ramping up the cell’s production of new proteins. In muscle tissue, that means faster repair and growth. The drugs also improve nitrogen retention, a marker of whether the body is building more protein than it breaks down. This is the core mechanism behind the muscle-building effect that makes these drugs appealing to athletes and bodybuilders.
Because they are variants of testosterone, anabolic steroids also trigger many of the same changes testosterone does naturally: deeper voice, increased body hair, and shifts in fat distribution. These androgenic effects are inseparable from the muscle-building ones, which is why users experience both regardless of their goals.
Legitimate Medical Uses
Despite their reputation as performance-enhancing drugs, anabolic steroids have real clinical applications. The FDA has approved them for a handful of specific conditions:
- Low testosterone (male hypogonadism): the most common prescription use, for men whose bodies don’t produce enough testosterone on their own
- Delayed puberty: in adolescent boys who are significantly behind their peers in physical development
- Certain breast cancers: in women, as part of a broader treatment plan
- Pituitary gland disorders: when the gland fails to signal the testes to produce hormones
Doctors also prescribe them off-label for conditions like aplastic anemia, kidney failure, and muscle wasting from AIDS or cancer. In these cases, the goal is to help the body maintain or rebuild tissue it would otherwise lose. Prescribed doses are far lower than what recreational users typically take.
Common Forms and How They’re Taken
Anabolic steroids come in oral tablets, injectable liquids, topical gels, and skin patches. Some of the most commonly prescribed versions include testosterone cypionate (an injectable sold as Depo-Testosterone), oxandrolone (an oral tablet sold as Oxandrin), and stanozolol (sold as Winstrol). Each has a slightly different chemical structure that changes how long it stays active in the body and how strongly it promotes muscle growth versus androgenic effects.
Some steroids were developed exclusively for veterinary use. Trenbolone acetate, for example, is FDA-approved only as an ear implant pellet for cattle to promote growth before slaughter. It has no approved human formulation, yet it remains one of the most widely misused anabolic steroids in bodybuilding circles.
Effects on the Heart and Cardiovascular System
The cardiovascular risks of anabolic steroid use are well documented. A study published in the American Heart Association’s journal Circulation compared weightlifters who used steroids with nonusers of similar age and training habits. Users had noticeably thicker heart walls and greater overall heart mass, averaging 245 grams compared to 192 grams in nonusers. That thickening isn’t the beneficial kind you get from endurance exercise. It’s a structural change that makes the heart stiffer and less efficient at pumping blood.
For every incremental increase in heart mass, users showed a measurable drop in how well their hearts contracted and relaxed. Steroid users were also nearly twice as likely to have LDL (“bad”) cholesterol above 160 mg/dL. Over time, this combination of a thickened heart and unhealthy cholesterol levels raises the risk of heart attack and heart failure, even in otherwise young, fit individuals.
Effects on Hormones and Fertility
When you flood the body with synthetic testosterone, it reads the signal as “there’s plenty already” and shuts down its own production. The brain stops sending hormones to the testes, which causes them to shrink and dramatically reduce sperm production. This feedback loop is one of the most predictable consequences of steroid use.
The fertility impact is significant. Sperm counts can drop to near zero during active use. After stopping, the body’s hormone system can recover, but the timeline varies widely. Some men regain normal sperm production within a few months, while others need a year or more. Prolonged or heavy use can extend recovery further, and in some cases full recovery is uncertain.
Other Physical Side Effects
Beyond the heart and hormonal system, anabolic steroids affect nearly every organ system. In the liver, oral steroids in particular can cause damage ranging from mild inflammation to more serious conditions like liver cysts. The skin responds with increased oil production, leading to severe acne on the back, shoulders, and face. In men, excess testosterone gets partially converted to estrogen, which can cause breast tissue growth (a condition users call “gyno”).
Women who use anabolic steroids experience masculinizing effects: facial hair growth, a deepening voice, menstrual irregularities, and clitoral enlargement. Many of these changes are only partially reversible after stopping. Adolescents face the additional risk of premature closure of growth plates, which can permanently limit their adult height.
Legal Status and Anti-Doping Rules
Possessing anabolic steroids without a prescription is a federal crime in the United States. As Schedule III controlled substances under the Controlled Substances Act, illegal possession can carry penalties including fines and up to one year in prison for a first offense, with harsher penalties for distribution.
In competitive sports, the rules are even stricter. The World Anti-Doping Agency (WADA) classifies all anabolic androgenic steroids as “non-specified substances” on its prohibited list, meaning they are banned at all times, both in and out of competition. There is no threshold or permitted amount. WADA’s list includes dozens of specific compounds, covering not just well-known steroids but also precursors and designer variants created specifically to evade testing. Athletes who test positive face suspensions typically ranging from two to four years.