This article is written specifically for men under 25. If that's not you, the full AAS educational reference covers the broader picture. If it is you — read this first.
The Conversation That's Not Happening
If you spend time in gym culture, on bodybuilding forums, in fitness YouTube comments, or in Instagram fitness communities, you have seen anabolic steroids normalised. You've seen 19-year-olds posting cycle logs. You've seen physique influencers at 21 or 22 who are clearly not natural — and the comment section isn't questioning it, they're asking what they're running.
There is an enormous amount of content online that will tell you how to run a cycle. There is almost no content that will honestly tell you why, if you are under 25, the calculation is categorically different to what it is at 30 or 35.
This article is that content.
It is not a lecture. It is a clinical picture. You're an adult capable of making decisions when given accurate information. The problem is that the information you're likely getting from online sources is heavily skewed toward the upside and almost silent on the genuine, documented downside.
The Biology First
Your testosterone axis is still developing
Most people believe that male development ends at 18. This is roughly true for height, but it is not true for the hormonal axis. The hypothalamic-pituitary-gonadal (HPG) axis — the system that regulates testosterone production — continues its functional maturation into the early-to-mid twenties in most men.
Here's what that means practically: your hypothalamus and pituitary are still establishing the baseline sensitivity, pulse patterns, and feedback loops that will govern your hormonal function for the next 50+ years. This is not abstract — it is the literal physiological infrastructure of your endocrine system.
When you introduce exogenous androgens (any anabolic steroid), you suppress this system. The hypothalamus and pituitary detect the elevated androgens and shut down their own signalling. Testosterone production from the testes stops. The system goes dormant.
In most adults with a fully mature HPG axis, this is recoverable over 3–6 months with proper PCT. In some, it's not fully recoverable. In men under 25, whose axis hasn't finished developing, the risk of permanent disruption is higher — and the clinical evidence supports this.
[Source: Rahnema CD et al., 2014 — Anabolic steroid-induced hypogonadism: diagnosis and treatment — Fertility and Sterility, 101(5):1271–9]
The Leydig cell problem
Testosterone is produced by Leydig cells in the testes. These cells respond to LH signals from the pituitary. When LH is suppressed by exogenous androgens, Leydig cells are left without stimulation — they atrophy.
In mature men, this atrophy is largely reversible. In younger men, Leydig cells are still in a sensitive developmental state. There is clinical evidence that Leydig cell damage from early AAS exposure can cause lasting impairment of testosterone production capacity. Not always. Not definitively in every case. But the risk of permanent reduction in endogenous testosterone production capacity is meaningfully higher when the system is disrupted during its development.
[Source: Jiang X et al., 2019 — Anabolic steroids and male infertility: a comprehensive review — BJU International]
Bone growth plates
This is the most overlooked risk for younger readers. The epiphyseal plates — growth plates at the ends of your long bones — are responsible for skeletal lengthening. They remain open until they fuse, typically between ages 17–21 but with significant individual variation. Some men's growth plates don't fully fuse until 23–24.
High androgen exposure can accelerate fusion of open growth plates. This means premature closure. Your long bones stop growing earlier than they would have naturally.
The practical consequence: you may end up permanently shorter than your genetic potential. This isn't reversible. Once the plates close, they close.
[Source: Rogol AD et al., 2000 — Androgen effects on bone mass — Endocrinology and Metabolism Clinics]
You Are at Your Natural Peak
This is the part the cycle-promotion side of the internet never says clearly enough.
Testosterone in men peaks during the late teens and early-to-mid twenties. Your natural anabolic environment right now is the highest it will ever be without pharmaceutical intervention. The muscle-building signal from your own hormones is at its strongest. Muscle protein synthesis capacity per unit effort is at its highest.
What this means: the relative benefit of AAS at your age is lower than it will ever be, because you're already operating near the peak of the system they're designed to augment. And the relative risk is higher, because the system they disrupt is still developing.
This is the asymmetry that nobody in your gym's locker room is explaining to you.
The men who look the way you want to look at 21 or 22 while on a cycle? You don't know what their testosterone levels will look like at 30. You won't see the posts about their TRT prescription, their fertility struggles, or the Harley Street endocrinologist visit. That content doesn't get posted.
The Post-Cycle Hypogonadism Data
There is a well-documented clinical pattern: men who use AAS in their teens or early twenties and present with hypogonadism (clinically low testosterone) in their late twenties or thirties.
This is not rare anecdote. Endocrinologists who specialise in male hormones see this regularly. A 2020 survey of male reproductive endocrinologists found AAS-induced hypogonadism to be among the most commonly encountered causes of acquired hypogonadism in men under 35. [Source: Pastuszak et al. — Anabolic steroid use in men — Sexual Medicine Reviews]
These men — and there are many of them — are on TRT for life. Not because they want to be. Because the decision they made at 19 or 20 permanently impaired their ability to produce their own testosterone.
TRT is not a bad life. But it means:
- Injections for life (or gel application every day)
- Regular blood monitoring indefinitely
- Potential fertility impairment (TRT suppresses sperm production — most men on TRT cannot conceive without additional medical intervention)
- Dependence on a medication system and prescription access for the rest of their lives
That is the trade being made. Not just more muscle now. That.
The Psychological Picture
The research on AAS and mental health is clearer and more consistent than most people in these communities acknowledge.
A comprehensive review by Pope et al. (Harvard Medical School) documented three distinct psychological patterns with AAS use:
1. Dependence: A recognised pattern of AAS dependency exists. It develops through a cycle of: use → improved self-image and performance → cessation → physical and psychological withdrawal → restart. The trigger is often muscle dysmorphia — a form of body dysmorphic disorder where men perceive themselves as insufficiently muscular regardless of their actual development. AAS use in susceptible individuals accelerates and deepens this pattern.
2. Mood dysregulation on-cycle: Irritability, aggression, mood instability, and in some individuals hypomanic-like states are documented across multiple studies. These effects are dose-dependent and compound-dependent. They are real, not myth.
3. Post-cycle depression: During PCT and in the period post-cycle, as endogenous testosterone recovers slowly, depression is common. Energy, libido, and mood crater. In some men, particularly those with pre-existing vulnerability, this depression can be severe.
In a developing brain — which the human brain is until approximately age 25 (prefrontal cortex maturation is ongoing through the mid-twenties) — these psychological effects carry more risk. The neural architecture that governs impulse control, risk assessment, and emotional regulation is still being finalised.
[Source: Pope HG et al., 2000 — Psychiatric and medical effects of anabolic-androgenic steroid use — Archives of General Psychiatry]
What Actually Happens at Your Age With Good Training
Here is an honest account of what a natural man aged 18–24 can achieve with serious, consistent, well-programmed training and appropriate nutrition:
Year 1 (new to training): 8–15kg of lean muscle. This is the fastest gaining period of anyone's training life regardless of drug use. The stimulus-to-response ratio is highest when you're untrained.
Year 2–3: 4–8kg per year. Still substantial. You are becoming a materially different physical presence.
Year 4–5: 2–4kg per year. The rate is slowing but the absolute development is significant.
A man who trains hard and eats correctly from 18 to 23 will look genuinely impressive by any objective standard. The models and influencers you're comparing yourself to are: (a) often using PEDs, (b) often at very low body fat for a photo or competition that doesn't reflect their day-to-day appearance, and (c) professionally photographed and edited.
The frame of reference most young men are using to assess their own progress is deeply distorted.
If You're Still Going to Research This
This is an article on a harm reduction-oriented website. We're not under the illusion that writing "don't do it" stops all experimentation. Adults make their own decisions, and information does more good than silence.
If you're determined to continue researching AAS:
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Get comprehensive bloodwork first. Know your baseline hormone levels. Know your lipid profile. Know your liver function. If something goes wrong, you need to know what normal looks like for you. [Medichecks do a Male Hormone blood test for around £60]
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Read the full clinical picture. Not just the cycle logs on forums. Read the Rahnema 2014 paper. Read Baggish et al. on cardiovascular effects. Read Pope et al. on psychiatric effects. These are accessible on PubMed.
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Understand what PCT actually does and doesn't do. PCT can assist HPG axis recovery. It does not guarantee it. It does not address cardiovascular damage, hepatic stress, or psychological effects.
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Talk to a doctor. Not for permission — for baseline data and post-cycle monitoring. An endocrinologist or GP can monitor your hormones and flag non-recovery early, when intervention is most effective.
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Wait. The honest, unglamorous advice. At 25, your axis is more mature, your natural gains are largely made, the risk:benefit calculation looks different. At 19 or 20, you are making a much more consequential trade than the forums are telling you.
The Short Version
You are not missing out by waiting. You are at the biological peak of your natural anabolic potential. The men whose physiques you're comparing yourself to may well be trading their long-term endocrine health for short-term appearance — and you won't see the consequences posted publicly because those don't get likes.
The clinical evidence is consistent: early AAS use (under 25) carries meaningfully higher risk of permanent HPG axis disruption, fertility impairment, and post-cycle hypogonadism than use after full physiological maturity. These aren't theoretical risks. They're documented, they're treated in clinics, and they're irreversible in some cases.
If you're going to make this decision at some point — make it with the full picture. This article is part of that picture.
Key references: Rahnema CD et al., Fertility & Sterility, 2014; Jiang X et al., BJU International, 2019; Pope HG et al., Archives of General Psychiatry, 2000; Pastuszak AW et al., Sexual Medicine Reviews, 2016; Baggish AL et al., Circulation, 2017.