A prohormone is a substance the body uses as a raw material to manufacture a fully active hormone. In biology, this is a normal part of how your endocrine system works: insulin, for example, starts life as “proinsulin” before enzymes clip it into its final shape. But when most people search for prohormones, they mean the over-the-counter supplements that first flooded the market in the late 1990s, sold with the promise that they would convert into testosterone or similar anabolic hormones once swallowed. The reality of these supplements is more complicated than the marketing ever suggested, and the health risks are considerably more serious than most users expect.
The Biological Meaning Versus the Supplement Meaning
Your body naturally produces prohormones all the time. Pancreatic beta cells, for instance, first build proinsulin, then use a specific enzyme (PC1/3) to process it into the insulin that regulates your blood sugar.1PubMed. Revisiting Proinsulin Processing: Evidence That Human β-Cells Process Proinsulin With Prohormone Convertase (PC) 1/3 but Not PC2 Similar precursor-to-active-hormone pathways exist for thyroid hormones, cortisol, and sex hormones. In this sense, prohormones are a routine feature of human physiology.
The supplement industry borrowed the term to describe synthetic steroid precursors, compounds like androstenedione and androstenediol, that are one or two enzymatic steps away from testosterone. The idea was that by swallowing these precursors, your body’s own enzymes would convert them into testosterone, giving you the muscle-building and performance-enhancing benefits of anabolic steroids without the legal or medical baggage.2PubMed. Effects of prohormone supplementation in humans: a review That pitch turned out to be misleading in several important ways.
Do Prohormone Supplements Actually Build Muscle?
The answer depends heavily on which compound you are talking about. Older prohormones like androstenedione, the one that made headlines when Mark McGwire’s locker was spotted with a bottle in 1998, repeatedly failed to raise testosterone levels enough to matter. Studies on these early compounds found that oral administration did not effectively increase serum testosterone and failed to produce meaningful changes in lean mass, strength, or performance compared to placebo.3PubMed Central. Testosterone precursors: use and abuse in pediatric athletes Most of the ingested androstenedione was converted not into testosterone but into estrogens, which is essentially the opposite of what users wanted.
Later-generation prohormones were designed to be more potent. Some of these are chemically very close to outright anabolic steroids and are active hormones in their own right, not just precursors. One controlled study on a compound called 3β-hydroxy-5α-androst-1-en-17-one found that users gained about 6% lean body mass, lost roughly a quarter of their fat mass, and increased their squat one-rep max by about 14% over the study period, all significantly better than the placebo group.4PubMed. Prohormone supplement 3β-hydroxy-5α-androst-1-en-17-one enhances resistance training gains but impairs user health That is a real anabolic effect. But it came with a long list of health problems, which is the pattern that repeats across the entire category: the compounds that actually work are the ones that carry serious risks.
What Happens to Your Liver
The liver takes the first and hardest hit because oral prohormones pass directly through it after absorption from the gut. Many of these compounds are methylated, a chemical modification that helps them survive that first pass through the liver but also makes them toxic to liver cells.
Case reports have documented cholestatic jaundice, a condition where bile backs up and the skin and eyes turn yellow, after as little as ten weeks of prohormone use. In one military case, a service member developed this complication and required eight weeks off the supplement before bilirubin levels returned to normal. A second service member developed liver cell damage and severely disrupted cholesterol levels after just 21 days of use.5PubMed. Mission Compromised? Drug-Induced Liver Injury From Prohormone Supplements Containing Anabolic-Androgenic Steroids in Two Deployed U.S. Service Members In another case, a 31-year-old man taking a prohormone product called SUS500 developed acute hepatitis alongside noticeable personality changes; both resolved only after he stopped the supplement entirely.6PubMed. Acute hepatitis and personality change in a 31-year-old man taking prohormone supplement SUS500
These are not rare edge cases that required massive doses. They happened at doses commonly sold in retail packaging. The liver damage is often reversible if the user stops in time, but “in time” is doing a lot of work in that sentence. Many users do not get blood work done and have no idea their liver enzymes are spiking until symptoms like jaundice or severe fatigue appear.
Cardiovascular Damage
Prohormones wreck your cholesterol profile quickly and dramatically. The same controlled study that documented meaningful muscle gains also measured what was happening under the hood: HDL cholesterol (the protective kind) dropped by nearly 39%, LDL cholesterol (the harmful kind) rose by about 33%, and the LDL-to-HDL ratio surged by 120%.4PubMed. Prohormone supplement 3β-hydroxy-5α-androst-1-en-17-one enhances resistance training gains but impairs user health These are not subtle shifts. A change of that magnitude, sustained over months or years, substantially accelerates the buildup of plaque in arteries.
Case studies of anabolic steroid users, who are taking compounds that prohormones convert into, show even more alarming extremes. One bodybuilder who repeatedly cycled on and off steroids had his HDL drop by 90% and his LDL rise by 100% during active use.7International Journal of Sports and Exercise Medicine. Extremely Low HDL Cholesterol and Increased LDL Cholesterol Induced by the use of Anabolic Steroids in a Body Builder: A Case Study HDL levels that low are almost unheard of in non-users and represent a profound cardiovascular risk. The cardiovascular damage is particularly insidious because users tend to be young, visibly fit, and feel healthy, which makes them unlikely to seek medical attention or believe they are at risk for heart disease.
Kidney Stress and Damage
The kidneys are another organ that pays a price, though this gets far less attention than liver damage. The controlled prohormone study found that users experienced about a 20% rise in serum creatinine and an 18% drop in glomerular filtration rate, both markers that the kidneys are struggling to keep up.4PubMed. Prohormone supplement 3β-hydroxy-5α-androst-1-en-17-one enhances resistance training gains but impairs user health
A systematic review of kidney complications from anabolic-androgenic steroids found that problems range from mildly elevated creatinine to acute kidney injury, sometimes as a consequence of rhabdomyolysis or bile acid nephropathy from the concurrent liver damage. Long-term use has been linked to structural kidney changes including scarring and tubular atrophy.8PubMed Central. The potential effects of anabolic-androgenic steroids and growth hormone as commonly used sport supplements on the kidney: a systematic review Separately, researchers have identified direct renal toxicity and abnormal calcium handling as additional mechanisms through which these compounds damage kidney tissue.9PubMed. Kidney disease associated with androgenic-anabolic steroids and vitamin supplements abuse: Be aware! Because kidney damage progresses silently for a long time, users can lose significant function before they notice anything wrong.
Hormonal Shutdown and Fertility
Taking exogenous androgens, whether in the form of straight testosterone, anabolic steroids, or prohormones that convert into them, sends a signal to the brain that testosterone levels are high enough. In response, the brain dials down its own production signals, and the testes slow or stop producing both testosterone and sperm. This disruption of the hormonal feedback loop is one of the most predictable consequences of prohormone use.
For men of reproductive age, the fertility implications are serious. Sperm production can drop to zero during use and may take months to recover after stopping. While many men do eventually regain normal function, recovery is not guaranteed. Some users experience prolonged low testosterone symptoms after discontinuation, and not everyone’s hormonal axis fully rebounds.10PubMed Central. Strategies for Reversing Exogenous Testosterone-Induced Infertility The irony is hard to miss: many prohormone users are young men trying to optimize their physique, and in the process they may be undermining their ability to have children.
Psychological and Behavioral Effects
The psychological side effects of anabolic compounds are well documented, and prohormones that effectively deliver androgenic activity carry the same risks. Aggression, irritability, and mood swings are common enough that “roid rage” became a cultural shorthand, though the scientific picture is more nuanced than that phrase suggests. Significant psychiatric symptoms including aggression, violence, mania, and less frequently psychosis and suicidal behavior have been associated with steroid use. Long-term users may develop dependence, and withdrawal can bring its own constellation of symptoms including depression and fatigue.11PubMed. Behavioural manifestations of anabolic steroid use
Beyond general psychiatric effects, some prohormone products have caused personality changes dramatic enough to prompt medical evaluation. The SUS500 case mentioned earlier involved personality changes alongside liver injury, and both resolved after the supplement was discontinued.6PubMed. Acute hepatitis and personality change in a 31-year-old man taking prohormone supplement SUS500 It is worth noting that additional reported side effects of androgenic compound use include gynecomastia (breast tissue growth in men), severe acne, and hair loss.12The Journal of Clinical Endocrinology & Metabolism. The Health Threat Posed by the Hidden Epidemic of Anabolic Steroid Use and Body Image Disorders Among Young Men
The Post-Cycle Therapy Problem
Most experienced prohormone users know about “post-cycle therapy,” a self-administered recovery protocol typically involving drugs like human chorionic gonadotropin and selective estrogen receptor modulators, both of which stimulate the testes to resume normal function. The logic is straightforward: restart your body’s own hormone production after you have suppressed it with exogenous compounds.
The trouble is that this practice has no objective evidence of effectiveness in reducing the severity or duration of low-testosterone symptoms after a cycle. A survey of 470 men who used these compounds found that while post-cycle therapy was widely practiced, there was no evidence it actually shortened the recovery window or reduced withdrawal symptoms.13Substance Abuse Treatment, Prevention, and Policy. The use of post-cycle therapy is associated with reduced withdrawal symptoms from anabolic-androgenic steroid use: a survey of 470 men Users are essentially self-prescribing pharmaceutical drugs based on gym lore, which introduces its own set of side effects and risks without a proven benefit.
What Is Actually in the Bottle
Even if you have done your research and chosen a prohormone product with a known risk profile, there is a real chance the product does not contain what the label says. An international study of 634 nutritional supplements purchased across 13 countries found that about 15% of products that were not labeled as hormonal were contaminated with anabolic-androgenic steroids, mainly prohormones. Since that study, investigators have also found products deliberately spiked with full-strength anabolic steroids like metandienone, stanozolol, and oxandrolone, none of which appeared on the label.14PubMed. Nutritional supplements cross-contaminated and faked with doping substances
This means that even someone taking a supplement they believe is a mild legal product could unknowingly be ingesting a banned and potentially liver-toxic anabolic steroid. It also means that athletes who test positive for banned substances after taking contaminated supplements have limited legal recourse. Anti-doping agencies have become increasingly sophisticated at detecting prohormone use, using isotope ratio mass spectrometry to identify abnormal patterns in urinary steroid metabolites that can extend detection windows well beyond what older tests could manage.15PubMed. Sensitive detection of testosterone and testosterone prohormone administrations based on urinary concentrations and carbon isotope ratios of androsterone and etiocholanolone
Legal Status and How It Keeps Shifting
In the United States, the legal landscape for prohormones has been a moving target. The original wave of products, led by androstenedione, was sold legally as dietary supplements under the 1994 Dietary Supplement Health and Education Act, which placed the burden of proving a product unsafe on the FDA rather than requiring manufacturers to prove safety before sale. The Anabolic Steroid Control Act of 2004 specifically added many named prohormone compounds to the federal list of controlled substances. The Designer Anabolic Steroid Control Act of 2014 closed additional loopholes by covering compounds that were structurally similar to known steroids but had been tweaked just enough to fall outside prior definitions.
Despite these laws, new compounds continue to appear on the market. Manufacturers modify the chemical structure just enough to argue that the new molecule is not explicitly listed as a controlled substance, and it can take years for regulators to catch up. This cat-and-mouse dynamic means that whatever is currently available for sale is not necessarily legal, and what is legal is not necessarily safe. The regulatory gray zone is part of the appeal for some users, but it also means the compounds available at any given moment are often the least studied and least understood.
Why the Risk-Benefit Calculation Almost Never Works Out
The fundamental problem with prohormone supplements is that the ones that do not work are pointless, and the ones that do work are dangerous. The older compounds like androstenedione simply failed to raise testosterone meaningfully, making them expensive placebos. The newer, more potent compounds do produce measurable gains in muscle and strength, but they simultaneously damage the liver, tank your cholesterol, stress the kidneys, suppress your own hormone production, and carry psychiatric side effects. That same study demonstrating genuine muscle gains also found liver enzyme elevations of over 100%, creatinine spikes, and a filtration rate drop significant enough to raise clinical concern, all in the span of a single cycle.4PubMed. Prohormone supplement 3β-hydroxy-5α-androst-1-en-17-one enhances resistance training gains but impairs user health
Many users rationalize the risks by telling themselves they will only run one or two cycles, get blood work done, and use post-cycle therapy afterward. In practice, the evidence for post-cycle therapy is weak, blood work often does not happen, and the pattern of use tends to escalate rather than stay contained. Add in the contamination problem, the shifting legal landscape, and the fact that these products are sold without meaningful quality control, and you have a category of supplements where the harms are well documented and the benefits, while real for some compounds, are inseparable from those harms.
Prohormone Use in Adolescents
A particularly concerning subset of prohormone users is teenagers and young adults. Adolescents are already in the middle of a hormonally driven growth process, and introducing exogenous androgenic compounds can interfere with normal development. In younger users, the stakes are higher because the hormonal disruption can affect bone growth plate closure, potentially limiting final adult height, and the developing brain may be more vulnerable to the psychiatric effects described in the literature.12The Journal of Clinical Endocrinology & Metabolism. The Health Threat Posed by the Hidden Epidemic of Anabolic Steroid Use and Body Image Disorders Among Young Men Reviews of testosterone precursor use in pediatric athletes have been blunt in concluding that these supplements do not effectively increase testosterone in younger populations and carry disproportionate risk relative to any possible benefit.3PubMed Central. Testosterone precursors: use and abuse in pediatric athletes
Body image disorders among young men are a significant driver of prohormone and anabolic steroid uptake. The pressure to achieve a muscular physique, amplified by social media, leads some young men toward these compounds before they have fully considered or understood the consequences. The clinical community has described this pattern as a hidden epidemic, one where the scale of use is difficult to measure because it happens outside medical supervision and users are often reluctant to disclose their supplement history to healthcare providers.