Steroids reduce inflammation or build muscle tissue, depending on the type. The word “steroids” actually covers two very different categories of drugs: corticosteroids, which calm your immune system, and anabolic steroids, which mimic testosterone and promote muscle growth. Both are powerful, both carry real risks, and they work through completely different mechanisms in your body.
Two Types With Very Different Jobs
Corticosteroids are the kind doctors prescribe most often. They work like cortisol, a hormone your adrenal glands naturally produce. Cortisol keeps your immune system from overreacting, and corticosteroid drugs do the same thing in a more targeted, potent way. They slow or stop the immune processes that trigger inflammation, which makes them useful for conditions like asthma, arthritis, allergic reactions, and autoimmune diseases.
Anabolic steroids are synthetic versions of testosterone. Their primary effect is increasing protein production inside muscle cells, which makes muscles grow larger and recover faster. Doctors prescribe them for a narrow set of conditions: men whose bodies don’t produce enough testosterone, delayed puberty in boys, certain types of breast cancer, endometriosis, and osteoporosis. Outside of medicine, they’re widely misused for athletic performance and bodybuilding.
How Corticosteroids Reduce Inflammation
When a corticosteroid enters your bloodstream, it passes through cell membranes and binds to a specific receptor inside the cell. That receptor then moves into the nucleus, where it directly interferes with the molecular signals that produce inflammation. It does this in two ways: it blocks the activity of proteins that would otherwise switch on inflammatory genes, and it tightens the packaging of DNA so those genes can’t be read as easily. The net result is that your body produces far fewer of the chemicals responsible for swelling, redness, heat, and pain.
Corticosteroids also boost production of a natural brake on inflammation. One of the key triggers of immune activation is a molecule that sits locked in the cell until an inflammatory signal frees it. Corticosteroids increase production of the lock itself, keeping that trigger contained. This is why these drugs can work so broadly, calming everything from a rash on your skin to inflamed airways in your lungs to swollen joints.
How Anabolic Steroids Build Muscle
Anabolic steroids bind to androgen receptors on muscle cells. Once bound, the steroid-receptor pair travels into the cell’s nucleus and activates genes that ramp up production of contractile proteins, the building blocks of muscle fibers. In clinical studies, a single injection of 200 mg of testosterone doubled the rate of net protein synthesis in healthy people, without changing how fast protein was broken down. The muscle simply built more of itself.
Beyond direct protein production, testosterone also activates satellite cells, which are essentially reserve cells that sit alongside muscle fibers. When a muscle fiber grows so large that its existing control centers can’t keep up, these satellite cells fuse into the fiber and donate their nuclei, allowing the muscle to sustain further growth. This is why anabolic steroids can push muscle size well beyond what training alone achieves.
How Steroids Are Delivered
Corticosteroids come in many forms, and the delivery method shapes how much of your body is affected. Inhaled steroids for asthma and topical creams for skin conditions deliver the drug locally, minimizing exposure to the rest of your body. Oral tablets and injections into muscle or veins are systemic, meaning the drug circulates everywhere. Doctors generally prefer local delivery when possible to reduce side effects, though even inhaled and topical steroids can suppress your body’s natural cortisol production if used at high doses for a long time.
Oral corticosteroids like prednisone reach peak levels in about two hours. Joint injections are used for localized pain and inflammation, with guidelines recommending a minimum of two to three weeks between injections and stopping the series once pain relief plateaus or becomes acceptable.
Anabolic steroids are taken orally or injected into muscle. People who misuse them often “stack” multiple types or “cycle” between on and off periods, but these patterns don’t eliminate the health risks.
Side Effects of Corticosteroids
Short courses of corticosteroids, lasting a week or two, are generally well tolerated. The problems accumulate with longer use. Up to 40% of patients on long-term corticosteroids develop bone loss severe enough to cause fractures, and this bone thinning can begin within the first six to twelve months of therapy. Weight gain and changes in fat distribution are common and dose-dependent, with fat shifting to the face, upper back, and trunk even at relatively low daily doses.
Blood sugar rises in a dose-dependent pattern. People with diabetes often find their glucose much harder to control while taking these drugs. For people with normal blood sugar, the spikes are usually temporary, though anyone receiving a steroid injection into a joint should monitor their blood sugar carefully for at least 48 hours and potentially up to a week afterward.
Other long-term effects include thinning skin, increased susceptibility to infections (since the immune system is suppressed), cataracts, elevated blood pressure, and mood changes ranging from irritability to insomnia to, in some cases, significant anxiety or depression.
Risks of Anabolic Steroid Misuse
The cardiovascular risks are the most serious concern. Imaging studies of long-term users, particularly bodybuilders and powerlifters, have found pathological thickening of the heart muscle. Unlike the healthy heart enlargement that comes from endurance exercise, steroid-induced thickening reduces the heart’s flexibility and pumping efficiency, and can progress to heart failure. Anabolic steroids also distort cholesterol levels, lowering the protective HDL type and raising LDL, which accelerates artery disease.
The hormonal fallout is equally significant. Flooding the body with synthetic testosterone signals the brain to stop ordering natural production. Over time this causes the testicles to shrink, sperm counts to drop to zero, and erectile function to decline. Some of these changes reverse after stopping, but long-term use can cause irreversible damage to the body’s hormone-regulating systems.
In women, anabolic steroids can deepen the voice, cause facial hair growth, and disrupt menstrual cycles. In adolescents, they can prematurely fuse growth plates, permanently limiting height.
Why You Can’t Stop Corticosteroids Abruptly
If you take corticosteroids for more than a few weeks, your adrenal glands start producing less cortisol on their own. They effectively go dormant because the drug is doing cortisol’s job. If you stop the medication suddenly, your body has no cortisol from the drug and not enough from your own glands. This state, called adrenal insufficiency, can cause fatigue, body aches, dizziness, nausea, and in severe cases dangerously low blood pressure.
A gradual taper, slowly reducing the dose over days or weeks, gives your adrenal glands time to wake back up and resume normal cortisol production. The length of the taper depends on how long you’ve been taking the drug and at what dose, but it’s one of the most important parts of corticosteroid treatment to get right.