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# Performance-enhancing drugs: what they do to the body

- Table to know
- For completeness

Doping drugs push one part of physiology (muscle, red cells, alertness) beyond normal, and the body pays with predictable side effects.

Updated Nov 13, 2026

Also called: Doping, Anabolic-androgenic steroids, Blood doping

## Key points

- Exogenous androgens suppress LH and FSH by negative feedback: testicular atrophy, low sperm count and infertility; aromatization to estradiol causes gynecomastia.
- Androgen misuse lowers HDL, raises LDL and blood pressure, causes erythrocytosis and left ventricular hypertrophy, and raises liver injury risk with oral 17α-alkylated forms.
- In women, androgens cause voice deepening, clitoral enlargement, hirsutism and menstrual disturbance, some irreversible.
- EPO and blood transfusion raise hemoglobin and VO₂max, but increase viscosity, thrombosis, stroke and hypertension risk.
- Stimulants raise alertness and mask fatigue; harms include arrhythmia, hypertension, heat stroke and dependence.
- Diuretics are misused to lose weight quickly or to dilute urine; they cause dehydration and electrolyte disturbance.

## What it is

Performance-enhancing substances act on normal physiological pathways: androgens on muscle protein synthesis, erythropoietin and transfusion on red cell mass, growth hormone on IGF-1, stimulants on catecholamine signalling. Their harms follow from the same physiology, such as feedback suppression of the testes, thick blood, high blood pressure and arrhythmia. This page explains effects and harms by class only; it gives no regimens or advice.

## Classes of performance-enhancing substances: intended effect, mechanism and harms

| Class | Intended effect | Physiological mechanism | Main harms |
| --- | --- | --- | --- |
| Anabolic-androgenic steroids | More muscle mass and strength, faster recovery | Androgen receptor activation raises muscle protein synthesis and satellite cell activity | Testicular atrophy, infertility, gynecomastia, acne, low HDL, hypertension, LV hypertrophy, erythrocytosis, liver injury, mood changes, virilization in women |
| Erythropoietin and other erythropoiesis stimulants | More O₂ delivery and endurance | EPO receptor activation raises red cell production and hemoglobin | High hematocrit and viscosity, thrombosis, stroke, hypertension |
| Blood transfusion (blood doping) | Same as EPO | Directly raises red cell mass | Viscosity, thrombosis, infection and transfusion reactions |
| Growth hormone and IGF-1 | Muscle and connective tissue growth, fat loss | GH raises IGF-1, lipolysis and protein synthesis | Insulin resistance and diabetes, fluid retention, joint pain, carpal tunnel, acromegalic changes |
| Stimulants (amphetamine-type, cocaine, ephedrine-type) | Alertness, less fatigue, weight loss | Release or block reuptake of norepinephrine and dopamine | Tachyarrhythmia, hypertension, myocardial infarction, heat stroke, dependence |
| Beta-blockers | Steady hands in precision sports | Block β-adrenergic tremor and tachycardia | Bradycardia, fatigue, bronchospasm in asthma |
| Diuretics and masking agents | Rapid weight loss; diluting urine | Increase renal salt and water loss | Dehydration, hypokalemia, cramps, arrhythmia |

## Clinical notes

- A muscular young man with small testes, high hematocrit, low HDL and acne suggests anabolic steroid use; after stopping, the suppressed axis can take months to recover.
- A very high hematocrit in an endurance athlete living at low altitude should raise suspicion of EPO or transfusion; at altitude, local norms must be considered.
- Sudden cardiac death in athletes using stimulants or steroids may unmask or add to hypertrophic cardiomyopathy and other structural heart disease.

## Memory aid

Push one dial past normal and the feedback loops push back: the testes shrink, the blood thickens, the heart races.

## Test yourself

Think of the answer, then tap the question to see it.

## Why do anabolic steroids cause testicular atrophy and infertility?

Exogenous androgens feed back on the hypothalamus and pituitary, suppressing GnRH, LH and FSH; Leydig cells and spermatogenesis then shut down.

## Why do some men who misuse androgens develop gynecomastia?

Aromatase converts part of the androgen to estradiol, which stimulates breast tissue, while the body's own testosterone production is suppressed.

## How does EPO doping raise performance, and what is its main danger?

It raises red cell mass, O₂-carrying capacity and VO₂max; the higher hematocrit increases blood viscosity and the risk of thrombosis and stroke.

## Which lipid change is typical of anabolic steroid misuse?

A marked fall in HDL cholesterol, often with a rise in LDL, which raises cardiovascular risk.

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## Connections

## Related topics 5

- [Testosterone and its actions](https://durgical.com/en/physiology/testosterone-and-its-actions/)
- [Erythropoiesis and erythropoietin](https://durgical.com/en/physiology/erythropoiesis-and-erythropoietin/)
- [Growth hormone and IGF-1](https://durgical.com/en/physiology/growth-hormone-and-igf-1/)
- [The male gonadal axis and spermatogenesis](https://durgical.com/en/physiology/the-male-gonadal-axis-and-spermatogenesis/)
- [Exercise and training physiology](https://durgical.com/en/physiology/exercise-and-training-physiology/)

## Related conditions 3

- [Stimulant use disorder (cocaine, amphetamines)](https://durgical.com/en/conditions/stimulant-use-disorder/)
- [Polycythaemia vera](https://durgical.com/en/conditions/polycythaemia-vera/)
- [Hypertrophic cardiomyopathy](https://durgical.com/en/conditions/hypertrophic-cardiomyopathy/)

## In Pharmacology 3

- [Testosterone](https://durgical.com/en/pharmacology/testosterone/)
- [Epoetin alfa](https://durgical.com/en/pharmacology/epoetin-alfa/)
- [Growth hormone](https://durgical.com/en/pharmacology/classes/growth-hormone/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [Anabolic Steroids and Other Appearance and Performance Enhancing Drugs (APEDs)](https://nida.nih.gov/research-topics/anabolic-steroids) (National Institute on Drug Abuse (NIDA, NIH), 2024); [Anabolic Steroids: MedlinePlus](https://medlineplus.gov/anabolicsteroids.html) (MedlinePlus, US National Library of Medicine, 2024); [Adverse Effects of Anabolic-Androgenic Steroids: A Literature Review](https://pmc.ncbi.nlm.nih.gov/articles/PMC7832337/) (Healthcare (PMC), 2021); [Gynecomastia](https://www.ncbi.nlm.nih.gov/books/NBK430812/) (StatPearls (NCBI Bookshelf), 2025).

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