Male fertility and testosterone treatment: why they conflict

The testes make both testosterone and sperm under the control of pituitary hormones. When testosterone is supplied from outside, the brain senses high levels and reduces output of luteinising hormone and follicle-stimulating hormone. This lowers testosterone production inside the testes, which sperm production needs in high concentration. Testicular size often decreases, and sperm count can drop to very low levels.

• Tell the prescriber if you may want children now or in future.

• Consider a semen analysis before starting to establish a baseline.

• Discuss sperm banking if appropriate, particularly for younger men.

• Ask about alternatives that preserve fertility.

• Understand that a partner's contraception needs may continue, since sperm may still be present.

In men with secondary hypogonadism, where the testes are healthy but receive too little stimulation, specialists sometimes use medicines such as clomifene, enclomifene or human chorionic gonadotrophin injections to stimulate the testes. Many of these are used off-label, and evidence about long-term outcomes is limited. They are used under specialist supervision with monitoring of hormones and semen parameters. Not every man is suitable, and treatment of the underlying cause, such as obesity or opioid use, can help.

After stopping testosterone, sperm production often recovers, usually over several months, but recovery varies and depends on age, duration of use, dose and baseline fertility. Some men take longer than a year, and a minority do not fully recover. Specialists may use stimulating medicines to speed recovery. Men planning conception should discuss a timeline well in advance.

Non-prescribed anabolic steroids and testosterone used for bodybuilding have the same suppressive effect and are often used at higher doses. Men who have used them and wish to conceive should speak to a doctor. Clinicians can help without judgement and arrange tests.

Couples who have not conceived after a year of regular unprotected sex, or sooner if there are known risk factors, should seek assessment. Semen analysis is a core test. A fertility specialist can assess male and female factors and suggest options, including assisted conception when appropriate.

Ask whether your low testosterone is due to a problem in the testes or in the pituitary, which affects fertility options. Ask whether a fertility-sparing treatment is suitable, what monitoring it needs and what the evidence is. Ask about the effect of your current medicines and lifestyle, such as weight, alcohol and opioids, on sperm. If you are already on testosterone, ask how long to wait after stopping before trying to conceive and when to have a semen analysis. Ask who will coordinate your care between endocrinology and fertility services.