Anabolic steroids, more precisely called anabolic-androgenic steroids (AAS), are a broad family of hormones related to testosterone. Although these compounds share the ability to activate the androgen receptor, relatively small changes to their chemical structure can substantially alter how they are metabolized and how their effects appear in different tissues.
That is why terms such as testosterone-based steroids, DHT derivatives, and 19-nor steroids are commonly used when discussing anabolic steroids.
Understanding these categories is useful for learning steroid pharmacology, interpreting medical literature, and understanding why different AAS can produce different biological effects. It is important to distinguish that educational classification from the idea that one category is inherently “safe.” Non-prescribed anabolic steroid use can carry significant cardiovascular, reproductive, hepatic, psychiatric, and endocrine risks.
What Are Anabolic Steroids?
Anabolic-androgenic steroids are natural or synthetic compounds that act primarily through the androgen receptor (AR). The term “anabolic” refers broadly to effects such as promoting protein synthesis and tissue growth, while “androgenic” describes effects associated with male sexual development and androgen activity.
Testosterone is the physiological reference point for many AAS classifications. Synthetic steroids modify the testosterone structure in different ways to change properties such as metabolism, duration of action, receptor interactions, and susceptibility to conversion into other hormones.
One important point is that anabolic steroids do not all behave identically after entering the body. Some can be converted into other active steroids, while structural modifications can prevent particular metabolic pathways.
The Main Categories of Anabolic Steroids
There is no single universally accepted classification system for every anabolic steroid. However, three structural families are particularly useful for understanding the subject:
- Testosterone and testosterone derivatives
- DHT-derived steroids
- 19-nor steroids
There are also additional structural distinctions, including modifications that affect oral bioavailability, metabolism, and estrogen formation.
Let’s examine each category.
1. Testosterone-Based Anabolic Steroids
Testosterone is the natural starting point for understanding anabolic-androgenic steroids.
Testosterone itself can interact directly with the androgen receptor. It can also undergo enzymatic conversion into other hormones. In particular, the enzyme 5-alpha-reductase converts testosterone into dihydrotestosterone (DHT) in certain tissues, while aromatase can convert testosterone into estradiol.
This metabolism helps explain why testosterone can have effects beyond its direct interaction with the androgen receptor.
What does “testosterone base” mean?
The phrase testosterone base can be confusing because it may refer to testosterone without an ester attached rather than to a completely different anabolic steroid.
Testosterone esters are chemical modifications used primarily to alter pharmacokinetic properties. Once an esterified testosterone preparation is metabolized, the active hormone is ultimately testosterone.
Therefore, “testosterone base” and “testosterone ester” should not be treated as completely different hormones. The distinction is primarily related to how the drug is formulated and released.
2. DHT Derivatives
Dihydrotestosterone (DHT) is another major reference point in anabolic steroid chemistry.
DHT is produced naturally when testosterone undergoes 5-alpha reduction. It has a high affinity for the androgen receptor, and its biological effects differ from testosterone because it cannot simply follow the same aromatization pathway as testosterone.
A number of synthetic anabolic steroids are structurally related to DHT and are therefore commonly called DHT derivatives.
Examples discussed in pharmacology include compounds such as:
These compounds are chemically related to DHT, but that does not mean they behave exactly like DHT in the body. Structural modifications can dramatically change metabolism, receptor activity, tissue effects, and duration of action.
Why are DHT derivatives different?
One important distinction is aromatization.
Testosterone can be converted by aromatase into estradiol. DHT itself does not undergo that same aromatization pathway. However, the broader category of DHT-derived anabolic steroids is chemically diverse, so it is inaccurate to assume that every DHT derivative has identical hormonal properties.
This is an important example of why steroid classification should be based on chemistry and pharmacology rather than bodybuilding terminology alone.
3. 19-Nor Steroids
The term 19-nor describes a structural modification in which the carbon at position 19 is absent compared with the testosterone structure.
The best-known example is nandrolone, also known as 19-nortestosterone. Another popular example is trenbolone.
Research into 19-norandrogens demonstrates why structural differences can have substantial consequences for steroid metabolism. When 19-nortestosterone is metabolized through 5-alpha-reductase, it does not simply become DHT. Instead, it forms a different metabolite with different androgen-receptor characteristics.
This helps explain why the biological effects of a 19-nor steroid cannot simply be predicted by looking at testosterone or DHT alone.
Why are 19-nors important?
The 19-nor modification changes the molecule’s interaction with metabolic enzymes and androgen receptors.
Scientific literature has specifically examined how these metabolic differences influence the relative anabolic and androgenic activity of 19-nor compounds.
Again, however, “19-nor” should be understood as a chemical classification, not a safety classification.
Oral Steroids and Structural Modifications
Another important way to categorize anabolic steroids is by their chemical modifications rather than their parent hormone.
Some orally active anabolic steroids contain structural changes that make them more resistant to metabolism in the liver. A well-known example is 17-alpha alkylation.
This modification can improve oral bioavailability, but it can also contribute to liver toxicity. Scientific reviews specifically identify orally administered 17-alpha-alkylated androgens as hepatotoxic.
This illustrates an important principle:
A chemical modification that improves one pharmaceutical property can introduce a different biological cost.
Consequently, “oral versus injectable” is not itself a sufficient way to determine the risk profile of an anabolic steroid.
How Anabolic Steroids Work
Most anabolic-androgenic steroids exert their principal effects through the androgen receptor.
After entering cells, an androgen can bind the receptor directly or, depending on the compound and tissue, undergo metabolism into another active steroid. The hormone-receptor complex can then influence gene transcription and protein production.
The body’s steroid metabolism therefore matters enormously.
Two compounds can both activate the androgen receptor while producing different effects because they:
- Have different chemical structures
- Are metabolized differently
- Produce different active metabolites
- Interact differently with metabolic enzymes
- Have different tissue distributions
- Differ in their ability to undergo aromatization
This is one reason why simply ranking anabolic steroids from “mildest” to “strongest” can be scientifically misleading.
Testosterone, DHT Derivatives, and 19-Nors Compared
| Category | Structural relationship | Important metabolic concept |
|---|---|---|
| Testosterone | Natural androgen and reference structure | Can convert to DHT and estradiol |
| DHT derivatives | Structurally related to DHT | Diverse metabolism; properties vary substantially |
| 19-nor steroids | Lack the C19 carbon found in testosterone | Produce distinct metabolites compared with testosterone |
| 17-alpha-alkylated steroids | Modified for greater oral stability | Some have significant liver toxicity |
These categories overlap with other ways of classifying steroids. A compound can therefore be described using more than one structural or pharmacological characteristic.
Are Some Anabolic Steroids Safer Than Others?
This is where online discussions often become misleading.
A compound having less activity in one pathway does not necessarily make it “safe.” Anabolic steroids can affect multiple organ systems, including the cardiovascular and reproductive systems. Reported adverse effects include changes in cholesterol, hypertension, cardiomyopathy, liver injury, suppression of natural testosterone production, infertility, acne, mood changes, and other endocrine effects.
Risk can also depend on factors such as the compound, exposure, duration, individual susceptibility, underlying health conditions, and whether multiple substances are involved.
For that reason, claims that a particular steroid is “side-effect free” or universally “safe” are not supported by the medical literature.
Why Steroid Classification Matters
Understanding the difference between testosterone-based steroids, DHT derivatives, and 19-nors provides a useful framework for interpreting anabolic steroid pharmacology.
The key takeaway is that chemical structure influences metabolism, and metabolism influences biological activity.
Testosterone can be converted into DHT and estradiol. DHT-related compounds have different structural characteristics. 19-nor compounds alter the testosterone structure in a way that changes their metabolism. Other modifications, such as 17-alpha alkylation, can alter oral activity while introducing additional toxicity concerns.
These distinctions are much more scientifically useful than simply labeling steroids as “bulking” or “cutting” drugs.
Final Thoughts
The world of anabolic-androgenic steroids is chemically complex. Testosterone, DHT derivatives, and 19-nor steroids are useful broad categories, but they should not be interpreted as simple rankings of potency, effectiveness, or safety.
The same structural modification that changes a steroid’s activity can also change its metabolism and adverse-effect profile. Research has linked nonmedical AAS use with potentially serious cardiovascular, hepatic, reproductive, endocrine, and psychological consequences.