Steroids change your body by altering how your cells build protein, store fat, manage inflammation, and regulate hormones. The word “steroids” actually covers two very different drug classes: anabolic steroids, which mimic testosterone and promote muscle growth, and corticosteroids, which mimic cortisol and suppress inflammation. Most people searching this question are thinking about the muscle-building kind, so that’s where we’ll spend most of our time, with a section on corticosteroids at the end.
How Anabolic Steroids Build Muscle
Anabolic steroids are synthetic versions of testosterone. When they enter your body, they bind to androgen receptors inside muscle cells, triggering a chain of events that ramps up protein production. Your cells start reading more of the genes responsible for muscle growth, nutrient storage, and the activation of satellite cells, which are the repair crews that fuse into existing muscle fibers to make them larger. At the same time, steroids block signals that would normally break muscle tissue down, including pathways driven by cortisol, your body’s main stress hormone.
This process works through two separate speeds. The slower, “genomic” pathway involves steroids entering the cell nucleus and directly changing which genes get switched on or off. The faster pathway happens within minutes: steroids interact with receptors on the cell surface, activating a cascade that fires up a key growth regulator called mTOR. This is the same pathway that resistance training activates, which is why combining steroids with heavy lifting produces significantly more muscle growth than either one alone.
The net result is that your body builds protein faster than it breaks it down. Muscles get bigger, recover more quickly between workouts, and can handle higher training volumes. This is real and measurable, which is exactly why these drugs are so tempting and so difficult to regulate in sports.
What Happens to Your Heart
Your heart is a muscle, and anabolic steroids don’t distinguish between the muscles you want to grow and the ones you don’t. In the HAARLEM study, which tracked amateur strength athletes through a full steroid cycle, left ventricular mass increased by an average of 28 grams. The walls of the heart, both the septum and the back wall, thickened measurably. The heart’s pumping efficiency dropped by about 5%, and the chambers became stiffer, making it harder for the heart to fill with blood between beats.
These changes were linked to the weekly dose: the more steroids someone used, the more the heart grew. A thicker, stiffer heart is the same pattern seen in chronic high blood pressure and is a well-established risk factor for heart failure, arrhythmias, and sudden cardiac death. Some of these changes appear reversible after stopping, but the degree of recovery depends on how long and how heavily someone used.
Cholesterol and Blood Vessel Damage
Anabolic steroids create one of the most dramatic shifts in cholesterol that any drug can produce. On average, HDL cholesterol (the protective kind that helps clear fat from artery walls) drops by 52%, with one specific subfraction falling by as much as 78%. Meanwhile, LDL cholesterol (the type that contributes to plaque buildup) rises by about 36%. This combination accelerates atherosclerosis, the slow narrowing of arteries that leads to heart attacks and strokes. The effect begins quickly and persists for weeks to months after stopping.
Your Body Stops Making Its Own Testosterone
When you flood your system with synthetic testosterone, your brain gets the message that there’s more than enough. It responds by dialing down the signals that tell your testes to produce the real thing. In one documented case, after just eight weeks of steroid use, luteinizing hormone (the chemical messenger from the brain that triggers testosterone production) dropped to nearly undetectable levels, and the body’s own testosterone fell to a fraction of its normal value.
This shutdown is called hypothalamic-pituitary-gonadal axis suppression, and it’s not a subtle effect. Testicles physically shrink because they’re no longer being stimulated. Sperm production drops, sometimes to zero. For many users, natural hormone production bounces back after stopping, but recovery can take months, and some men experience prolonged or even permanent fertility problems after heavy, long-term use.
Breast Tissue Growth in Men
In a counterintuitive twist, flooding your body with testosterone can lead to breast development. Your body converts excess testosterone into estrogen-like compounds, and that estrogen stimulates breast tissue to grow. This condition, called gynecomastia, is common enough among steroid users that surgical correction has become a recognized part of plastic surgery practice. Once the tissue has formed, stopping steroids alone usually won’t reverse it.
Liver Stress
Oral anabolic steroids are processed through the liver, and this is where they do the most direct organ damage. Liver enzyme levels can rise, signaling that liver cells are under stress or dying. More serious but rarer complications include peliosis hepatis, a condition where blood-filled cysts form throughout the liver, and liver tumors ranging from benign growths to hepatocellular carcinoma. The exact incidence is hard to pin down because steroid use is underreported and many users never get liver imaging. Injectable steroids bypass the first pass through the liver and carry less hepatic risk, which is one reason experienced users often prefer them, though they still carry every other risk on this list.
Mood, Aggression, and Dependence
The psychological effects of anabolic steroids follow a pattern that researchers describe as biphasic: one set of symptoms while you’re on them, another when you come off. During a cycle, users may experience heightened aggression, irritability, and in some cases manic symptoms or even psychosis. The stereotype of “roid rage” is an oversimplification, but the link between supraphysiological testosterone levels and increased aggression and violence is well-documented in clinical literature.
The withdrawal phase brings its own problems. When steroid use stops, the body is left with suppressed natural hormone production and no external supply. This hormonal vacuum commonly produces depressed mood, severe fatigue, insomnia or excessive sleeping, loss of appetite, and a sharp drop in sex drive. These symptoms can persist for weeks or months and are a major driver of the dependency cycle: people resume steroids not necessarily to get bigger, but to escape feeling terrible. A global lifetime prevalence of anabolic steroid use sits around 3.3%, and dependence patterns that meet formal addiction criteria have been described in a meaningful portion of regular users.
Effects on Skin and Hair
Testosterone-derived steroids increase oil production in your skin, which is why severe acne, particularly on the back and shoulders, is one of the most visible signs of use. Hair loss accelerates in anyone genetically predisposed to male-pattern baldness, because the same androgenic activity that builds muscle also miniaturizes hair follicles on the scalp. In women, anabolic steroids trigger masculinization: deepening of the voice, facial hair growth, clitoral enlargement, and disruption of menstrual cycles. Some of these changes, particularly voice deepening, are irreversible.
Corticosteroids: A Different Drug Entirely
Corticosteroids like prednisone, hydrocortisone, and dexamethasone are anti-inflammatory drugs prescribed for asthma, autoimmune diseases, allergic reactions, and dozens of other conditions. They work by suppressing your immune system and reducing inflammation, which makes them invaluable for managing flare-ups but problematic over long stretches.
The side effects of long-term corticosteroid use look nothing like those of anabolic steroids. Instead of building muscle, corticosteroids break it down. Instead of thickening bones, they thin them. In a prospective study following children with asthma over a median of seven years, boys who received five or more courses of oral corticosteroids had measurably slower bone mineral growth and a 21% rate of osteopenia (early bone thinning), compared to 10% in boys who received none. Other common effects of prolonged use include weight gain concentrated in the face and abdomen, elevated blood sugar, thinning skin that bruises easily, and increased susceptibility to infections because the immune system is deliberately suppressed.
Short courses of corticosteroids, the kind prescribed for a week or two to manage a flare-up, generally don’t produce these long-term effects. The problems accumulate with repeated or continuous use over months and years, which is why doctors try to use the lowest effective dose for the shortest possible time.