antiandrogen
Meaning of antiandrogen: A drug that stops male hormones being heard, either by blocking the receiver or by cutting off the supply.
Definition of antiandrogen
An antiandrogen is a drug that opposes the action of androgens, the hormones such as testosterone that produce male characteristics. Most work by occupying the androgen receptor inside cells, so testosterone arrives but cannot switch anything on. Others lower androgen production instead. They are used chiefly in prostate cancer and in conditions driven by excess androgen activity.
What are the two ways of doing it?
| Approach | How it works | Effect on the blood testosterone level |
|---|---|---|
| Receptor blockade | The drug sits in the androgen receptor so the hormone cannot activate it | Unchanged or higher, since the feedback brake is blocked too |
| Blocking synthesis | An enzyme needed to build androgens is inhibited in the testicles, the adrenal glands and the tumor itself | Falls |
| Shutting off the signal | Drugs acting on the pituitary stop the message that tells the testicles to produce | Falls to very low levels |
All three are grouped loosely under hormone treatment, but only the first is an antagonist at the receptor in the strict sense, and the distinction changes what a testosterone result means during treatment.
What are they used for?
The largest use is in prostate cancer, where a receptor blocker may be added at the start of hormone injections to cover the initial surge, or used as the main treatment when disease continues despite low testosterone. Outside cancer, antiandrogens are prescribed for severe acne, unwanted hair growth and androgen-driven hair loss in women, for symptoms of polycystic ovary syndrome, and as part of gender-affirming hormone therapy. Some are also used in early puberty.
What side effects follow?
Blocking androgens produces effects that mirror their normal actions: hot flashes, breast tenderness and enlargement, loss of libido and erectile difficulty, fatigue, muscle loss and thinning of bone over prolonged use. Individual drugs add their own problems, including liver injury with a few of the older agents, diarrhea and rash, so liver blood tests are usual during treatment with certain of them. In women who could become pregnant these drugs interfere with the development of a male fetus, which is why contraception forms part of the treatment plan. Long-term antiandrogen therapy is also monitored for bone density and metabolic effects.
Also known as
Used in a sentence
An antiandrogen was added at the start of treatment to cover the initial testosterone surge.
Good to know
Blocking the androgen receptor does not lower the testosterone level and can raise it, so the single word antiandrogen covers drugs with opposite effects on a hormone blood test.
Word origin
Where “antiandrogen” comes from
Androgen joins the Greek andros, meaning of a man, with genes, meaning producing; the prefix anti- means against.