In men with confirmed hypogonadism, TRT has the clearest evidence for improving sexual desire. It may also increase lean mass and correct anaemia in some men. Important risks to monitor include raised haematocrit and reduced fertility; prostate health, blood pressure, thrombosis and atrial fibrillation also matter.
Which benefits are best supported?
In men with confirmed low testosterone and compatible symptoms, evidence is strongest for some sexual symptoms, particularly sexual desire. TRT can also increase lean mass and improve anaemia in some patients.
Changes in energy, mood, strength or erections are more variable because these symptoms often have several causes. If testosterone normalises but the original problem does not improve, the diagnosis should be reviewed.
Why is haematocrit so important?
Testosterone stimulates red-blood-cell production and can increase haematocrit, the proportion of blood made up of red cells. This occurs more often with some formulations and in predisposed people.
The EAU states that haematocrit above 54% during treatment requires action. Management can include adjusting the dose or interval, changing formulation, pausing treatment and looking for associated causes.
Does TRT cause prostate cancer?
The simple statement that TRT automatically causes prostate cancer does not reflect current evidence. Prostate health still matters because treatment can change PSA and known or suspected prostate cancer changes the treatment decision.
The need for PSA, examination or other tests depends on age, history, symptoms and individual risk. An unexpected PSA rise during follow-up should be investigated rather than ignored or attributed automatically to treatment.
Does TRT increase cardiovascular risk?
The TRAVERSE trial studied men with hypogonadism and increased cardiovascular risk. Testosterone did not increase major cardiovascular events compared with placebo during the study period. This is reassuring but does not mean TRT is cardiovascularly neutral for every person.
TRAVERSE reported more atrial fibrillation, acute kidney injury and pulmonary embolism in the testosterone group, and a substudy found more fractures. Individual assessment remains important, particularly after a recent cardiovascular event or when thrombosis risk is relevant.
Sources: TRAVERSE, N Engl J Med 2023 · Endocrine Society 2026.
Can TRT affect blood pressure?
Some preparations can increase blood pressure or fluid retention. Knowing baseline blood pressure and reviewing changes during treatment is particularly important in people with hypertension, heart failure or kidney disease.
What happens to fertility?
External testosterone suppresses LH and FSH, the signals the testes need to produce high intratesticular testosterone and sperm. Sperm counts can fall substantially and may reach azoospermia.
If you want children now or soon, say so before treatment starts. A fertility-preserving plan may be very different and can require specialist input.
What other adverse effects can occur?
- Acne or oilier skin.
- Changes in hair loss in predisposed people.
- Breast enlargement or tenderness in some patients.
- Skin reactions with gels or reactions at injection sites.
- Changes in sexual desire, including too little, too much or no change.
- Worsening of some sleep disorders in selected patients.
An adverse effect does not always mean treatment must stop permanently. Dose, formulation, diagnosis and contributing factors may need review.
What monitoring makes treatment safer?
Good follow-up asks three questions: is it working?, are testosterone levels appropriate? and is it causing problems? Testosterone and a full blood count with haematocrit are commonly monitored, with PSA and prostate assessment when appropriate.
The frequency and timing depend on the formulation and the individual's risk. Doses should not be changed simply to chase a number without considering symptoms, dose timing and adverse effects.
What do we still not know?
- Long-term safety, including prostate-cancer risk, is not fully established.
- TRAVERSE studied men with increased cardiovascular risk; its results cannot simply be applied to every man.
- There is no universal rule for how long treatment should continue when the cause is functional or potentially reversible.
More treatment does not mean more benefit
The aim is replacement into a physiological range, not exceeding it. Raising the dose to "optimise" energy, muscle or performance may increase risk without solving the true cause of symptoms.