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# Androgens

Testosterone and related steroids. They replace testosterone in male hypogonadism; weak androgens such as danazol suppress the pituitary-ovarian axis.

Updated Nov 1, 2026

## What they are

Testosterone (injectable esters, gels, patches, oral undecanoate) and synthetic derivatives that act on the androgen receptor. Testosterone replaces the hormone in men with primary or hypogonadotropic hypogonadism and induces puberty in delayed puberty. Danazol, a weak androgen and antigonadotropin, is used for endometriosis and to prevent attacks of hereditary angioedema. Anabolic-androgenic steroids are also misused to build muscle.

## Mechanism of action

Androgens bind the androgen receptor, a nuclear receptor, directly or after conversion of testosterone to dihydrotestosterone by 5-α-reductase; some testosterone is aromatised to estradiol. The receptor complex switches genes that develop and maintain male sexual characteristics, spermatogenesis, muscle, bone and erythropoiesis. Exogenous androgens also suppress LH and FSH, which lowers sperm production.

Target: Androgen receptor (AR), a nuclear receptor

## Key points

- Raised haematocrit (erythrocytosis) is a frequent dose-related effect; haemoglobin and haematocrit are checked.
- Contraindicated in breast or known/suspected prostate cancer and in pregnancy (virilisation of a female fetus).
- Exogenous testosterone suppresses LH and FSH and therefore spermatogenesis: it is not a fertility treatment.
- Abuse at high doses causes cardiovascular, psychiatric and liver problems; testosterone is a controlled substance.
- Danazol is teratogenic (virilises a female fetus) and can cause thrombosis, liver tumours and intracranial hypertension.

## Drugs in this class

- [**Testosterone** The main male sex hormone, given as injections, gels or patches to replace testosterone in men whose testes or… Androgen receptor (AR), a nuclear receptor](https://durgical.com/en/pharmacology/testosterone/)
- [**Danazol** A synthetic weak androgen that suppresses the pituitary-ovarian axis. Used for endometriosis and to prevent hereditary… Androgen and other gonadal steroid receptors; it suppresses pituitary FSH and LH](https://durgical.com/en/pharmacology/danazol/)

## Others in the class

- Methyltestosterone
- Fluoxymesterone
- Oxandrolone
- Nandrolone

## Test yourself

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

## Why does testosterone therapy lower sperm count?

Exogenous testosterone suppresses pituitary LH and FSH by negative feedback, so the testes produce less sperm.

## Which blood test rises with testosterone and must be monitored?

Haemoglobin and haematocrit (erythrocytosis), which increase the risk of thrombosis.

## Which two cancers contraindicate testosterone in men?

Breast cancer and known or suspected prostate cancer.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - TESTOSTERONE CYPIONATE injection](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=78d55bad-4a5b-4e21-aeb8-a4c6346208be) (DailyMed (U.S. National Library of Medicine), 2026); [Testosterone Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a614041.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [DailyMed - DANAZOL capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e19acee5-ff33-45a5-bbbf-801756bc59b4) (DailyMed (U.S. National Library of Medicine), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/classes/androgens/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/androgens/