The word “steroid” covers a wide range of substances, from the anti-inflammatory medications prescribed for asthma to the testosterone-related compounds associated with bodybuilding. Even within anabolic-androgenic steroids (AAS), compounds differ in chemical structure, how they are processed by the body, their medical status, and the side effects they are most associated with.
This guide explains the main types of steroids, how anabolic steroids are classified by chemical family, what distinguishes oral and injectable compounds, and which commonly discussed compounds have medical, veterinary, or no approved use.
What are the main types of steroids?
In medicine, “steroids” usually refers to one of two drug classes.
Corticosteroids, such as prednisone, are synthetic versions of adrenal hormones. They reduce inflammation and suppress immune activity and are used for conditions such as asthma, arthritis, and eczema. They do not build muscle, and long-term use can contribute to muscle loss.
Anabolic-androgenic steroids are testosterone and synthetic compounds related to it. They promote tissue building, particularly muscle, and produce male-typical characteristics.
Other hormones, including estrogens and progesterone, also share the steroid chemical structure. Our guide to the key facts about steroids explains these distinctions in more detail. The rest of this article focuses on AAS.
How do anabolic steroids work?
All AAS act mainly by binding to androgen receptors. This activates genes involved in muscle protein synthesis and also affects tissues such as skin, hair follicles, the prostate, the liver, the heart, and the brain. Our article on building muscle with anabolic steroids explains these mechanisms and what controlled research shows.
Because all AAS act on the same receptor, they share core effects, including suppression of the body’s own testosterone production. The differences between compounds lie mainly in how strongly they produce tissue-building versus male-typical effects, whether they can be converted to other hormones, and how they are processed by the body.
How are anabolic steroids classified?
AAS are usually grouped by the parent molecule they are derived from (Kicman, 2008). Compounds in the same family tend to share certain properties, although each compound has its own profile.
Testosterone and its esters
Testosterone is the primary male sex hormone and the reference point for all AAS. Pharmaceutical testosterone is commonly attached to an ester, a chemical group that changes how quickly it is released into circulation after injection.
Testosterone can be converted by the body into two other active hormones: dihydrotestosterone (DHT), through the enzyme 5-alpha reductase, and estradiol, an estrogen, through the enzyme aromatase. This means testosterone produces both androgenic effects and estrogen-related effects.
Testosterone is approved in the United States to treat male hypogonadism.
DHT-derived compounds
Several AAS are chemically derived from DHT. These include stanozolol, oxandrolone, oxymetholone, drostanolone, and methenolone.
Because DHT cannot be converted by aromatase into estrogen, most compounds in this family are not associated with estrogen-related effects in the way testosterone is. Several are orally active and chemically modified to survive processing by the liver, which is associated with liver strain and pronounced reductions in HDL cholesterol.
Nandrolone-family compounds
Nandrolone and trenbolone are derived from 19-nortestosterone, a form of testosterone missing one carbon atom. Compounds in this family can also act on progesterone receptors, which gives them effects that differ from testosterone-derived compounds.
Nandrolone has been used medically, mainly for anemia associated with kidney disease. Trenbolone was developed for veterinary use in livestock and has never been approved for human use.
Other testosterone-derived compounds
Some AAS are modified forms of testosterone itself. Methandrostenolone and boldenone are examples. Small structural changes alter how strongly these compounds produce tissue-building effects relative to male-typical effects, and how readily they are converted to estrogen.
The balance between tissue-building and male-typical effects is often summarized as an “anabolic-to-androgenic ratio.” Our article on anabolic vs androgenic effects explains why these ratios, which come from animal testing, are less meaningful in humans than they are often presented.
Oral vs injectable steroids
How a compound is taken is closely linked to its chemistry.
Injectable steroids
Most injectable steroids are attached to an ester that controls how quickly the compound is released after injection. Longer esters release more slowly and remain active for longer, while shorter esters act more quickly.
Oral steroids
Most oral steroids are modified through 17-alpha-alkylation, a change that prevents the liver from breaking them down too quickly after they are swallowed. This modification is the main reason oral AAS are associated with liver strain, rare but serious liver conditions, and more pronounced effects on cholesterol than many injectable compounds.
Medical, veterinary, and unapproved compounds
Many commonly discussed AAS have no current approved use in humans in the United States. Their status differs considerably:
Testosterone is approved for treating male hypogonadism.
Oxymetholone has been approved for treating certain types of anemia.
Nandrolone has been used for anemia associated with kidney disease, although its availability as an approved product has been limited.
Oxandrolone was approved in 1964, but the FDA withdrew approval of all oxandrolone tablets in June 2023 and later determined that the drug had been withdrawn from sale for reasons of safety or effectiveness (FDA, 2023).
Stanozolol is no longer marketed for human use in the United States.
Methandrostenolone has no approved human use in the United States.
Trenbolone and boldenone were developed for veterinary use and have never been approved for humans.
Products sold outside the regulated pharmaceutical supply, including compounds originally intended for animals, are not subject to the quality controls required for human medicines.
Substances often confused with steroids
Several substances discussed alongside AAS are not steroids:
SARMs (selective androgen receptor modulators) act on androgen receptors but have a different, non-steroidal structure. None are approved for medical use in the United States.
Clomiphene and tamoxifen are selective estrogen receptor modulators, not steroids.
Aromatase inhibitors, such as anastrozole, block the conversion of androgens to estrogen. They are not anabolic steroids.
Tadalafil (Cialis) is a medication for erectile dysfunction and enlarged prostate. It is not a steroid.
Why “mild” and “bulking” labels are misleading
Compounds are often described informally as “mild,” “bulking,” or “cutting.” These labels come from user culture rather than pharmacology. A compound described as mild may still cause significant side effects, and oral compounds marketed as mild are among those most associated with liver strain and lipid changes.
Regardless of type, all AAS suppress the body’s natural testosterone production. Our article on testosterone recovery after steroids explains why recovery after use can take months or longer. Overall risk depends on the compound, dose, duration of use, the use of multiple compounds, and individual factors, and no type of AAS is risk-free (Pope et al., 2014).
Are all types of anabolic steroids regulated the same way?
In the United States, substances that meet the legal definition of an anabolic steroid are Schedule III controlled substances, regardless of chemical family, and can be legally obtained only with a valid prescription (DEA, 2025). In competitive sport, all anabolic agents are prohibited at all times under the World Anti-Doping Agency Prohibited List. Our article on steroid industry regulation covers the regulatory landscape in more detail.
The bottom line
The main types of steroids are corticosteroids, which reduce inflammation, and anabolic-androgenic steroids, which are related to testosterone. Within AAS, compounds are classified by chemical family: testosterone and its esters, DHT-derived compounds, nandrolone-family compounds, and other testosterone derivatives.
These families differ in whether they can be converted to estrogen, how they are processed by the liver, and their medical status. Many commonly discussed compounds have no approved human use in the United States, and some were developed only for veterinary use. Despite these differences, all AAS suppress natural testosterone production and carry health risks. Anyone with questions about steroid use and their health should speak with a qualified healthcare professional.
References
Drug Enforcement Administration. Anabolic steroids: drug fact sheet. DEA Diversion Control Division. Accessed October 2026.
Food and Drug Administration. Determination that Oxandrin (oxandrolone) tablets, 2.5 milligrams and 10 milligrams, were withdrawn from sale for reasons of safety or effectiveness. Federal Register. 2023;88 FR 62799.
Kicman AT. Pharmacology of anabolic steroids. British Journal of Pharmacology. 2008;154(3):502–521. Pope HG Jr, Wood RI, Rogol A, Nyberg F, Bowers L, Bhasin S. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocrine Reviews. 2014;35(3):341–375.
