Testosterone Replacement Therapy Explained
Testosterone replacement therapy (TRT) is a medical treatment for men who have symptoms of testosterone deficiency together with repeatedly low testosterone levels on properly timed blood tests. It is not a general energy, bodybuilding or anti-ageing treatment. TRT can improve sexual symptoms, anaemia, bone health and body composition in appropriately selected men, but it requires follow-up because it can raise the blood haematocrit, affect the prostate monitoring pathway and suppress sperm production. Men who are trying to father a child usually need a fertility-preserving approach instead of standard testosterone replacement.
What is testosterone replacement therapy?
TRT replaces testosterone when the body is not producing enough. The medical term is male hypogonadism. The aim is to restore testosterone into the physiological range and improve symptoms attributable to deficiency, not to push levels above normal.
A low laboratory value alone does not automatically mean TRT is needed. Diagnosis usually requires compatible symptoms plus consistently low testosterone, measured with an appropriate assay and confirmed on another morning sample. The cause of low testosterone should also be assessed.
Who may benefit from TRT?
TRT may be considered when a man has confirmed hypogonadism and symptoms that are clinically meaningful.
- Reduced sexual desire or fewer spontaneous erections when low testosterone is confirmed.
- Reduced muscle mass or strength associated with established hypogonadism.
- Low bone density or osteoporosis in some men with androgen deficiency.
- Unexplained anaemia in selected men after other causes are considered.
- Classical testicular or pituitary causes of testosterone deficiency.
How is low testosterone confirmed before treatment?
A careful assessment prevents unnecessary or unsafe treatment. Your doctor may review symptoms, medicines, sleep, weight, alcohol use, chronic illness and fertility plans.
- Morning total testosterone, usually repeated on a separate day.
- Free testosterone or SHBG when total testosterone is difficult to interpret.
- LH and FSH to distinguish testicular from pituitary/hypothalamic causes.
- Prolactin or pituitary evaluation when indicated.
- Haemoglobin/haematocrit before treatment.
- PSA and prostate assessment when appropriate for age and risk.
- Fertility history and semen testing when future fatherhood matters.
Three questions to answer before the first TRT prescription
Before discussing brand or dose, three decisions matter more: is hypogonadism genuinely confirmed, what is causing it, and could biological fatherhood matter now or later? Missing any one of these can turn a reasonable treatment into the wrong treatment.
- Is testosterone low on properly timed repeat testing, and do the symptoms actually fit androgen deficiency?
- Is the cause potentially reversible – for example obesity, untreated sleep apnoea, acute illness or a medication effect – or is there a testicular/pituitary disorder that needs specific evaluation?
- Would suppression of sperm production be unacceptable? If future fertility matters, standard exogenous TRT is usually not the first conversation to have.
This is why a good TRT consultation often spends more time on diagnosis than on choosing an injection or gel.
What forms of testosterone therapy are available?
The best formulation depends on availability, cost, convenience, symptom response, safety monitoring and the patient’s preference. Brand and dose should be individualised by the treating doctor.
| Form | Practical points |
|---|---|
| Injections | Can be short- or longer-acting depending on preparation; levels and dosing intervals differ by product. |
| Skin gel | Applied regularly to skin; transfer to partner or child must be prevented until dry and covered as instructed. |
| Other formulations | Patches, oral/buccal or implant formulations exist in some regions; availability varies. |
What benefits can TRT provide?
Benefits vary. Sexual desire and some sexual symptoms may improve when low testosterone is genuinely contributing. Lean body mass and bone density can improve over time. Some men with anaemia related to testosterone deficiency may show improvement.
TRT is less likely to solve fatigue, low mood or erectile dysfunction when those symptoms are mainly due to obesity, diabetes, sleep apnoea, depression, medication effects, vascular disease or relationship factors. Treating those contributors remains important.
Testosterone replacement therapy and fertility
Standard exogenous testosterone suppresses LH and FSH signals from the pituitary. This can markedly reduce sperm production and may cause severe oligospermia or azoospermia.
AUA/ASRM and EAU guidance advise against testosterone therapy for men who are actively trying to conceive. If fertility is important, discuss this before the first dose. Depending on the cause, fertility-preserving hormonal approaches may be considered by an andrologist or fertility specialist.
Who should not start TRT without specialist evaluation?
- A man currently trying to conceive.
- Known or suspected prostate or breast cancer until appropriately evaluated.
- High haematocrit or an unexplained rise in red blood cell count.
- Untreated severe obstructive sleep apnoea or significant uncontrolled medical illness.
- Recent major cardiovascular event or significant thrombosis risk where specialist review is needed.
- Unexplained markedly abnormal PSA or a suspicious prostate examination.
Monitoring after starting TRT
TRT is not a “start and forget” treatment. Follow-up checks confirm that symptoms improve and that treatment remains safe.
- Symptom response and adverse effects.
- Serum testosterone at a timing appropriate to the formulation.
- Haemoglobin and haematocrit.
- PSA/prostate monitoring according to age, baseline risk and shared decision-making.
- Blood pressure, weight and cardiometabolic health where relevant.
- Fertility discussion if plans change.
When TRT needs prompt medical review
- New chest pain, severe breathlessness or neurological symptoms.
- Painful swollen leg or symptoms suggesting a blood clot.
- Severe headache, marked facial flushing or symptoms with a very high haematocrit.
- Inability to pass urine or rapidly worsening urinary symptoms.
- Any concerning reaction after an injection or severe skin reaction to a topical product.
TRT consultation checklist
Bring these if available:
- Two morning testosterone reports if already tested.
- LH, FSH, prolactin and SHBG/free testosterone reports if done.
- CBC/haemoglobin/haematocrit.
- PSA report if tested.
- List of current medicines and supplements, including gym or “testosterone booster” products.
- History of fertility plans, children and any semen analysis.
- Reports for diabetes, thyroid disease, sleep apnoea or pituitary problems if relevant.
FAQs
Is TRT the same as taking steroids for bodybuilding?
No. Medical TRT aims to restore testosterone into a normal physiological range in men with confirmed deficiency. Supraphysiological anabolic steroid use has different goals and risks.
Will TRT improve erections?
It may help if testosterone deficiency is contributing, especially when low libido is also present. Many men with ED have vascular, diabetic, medication or psychological causes that need separate treatment.
Does TRT permanently stop fertility?
Sperm production often recovers after stopping exogenous testosterone, but recovery can take months and occasionally longer. Do not assume recovery will be immediate or complete.
How long is TRT needed?
That depends on the cause. Classical permanent hypogonadism may require long-term replacement. Functional low testosterone may improve if reversible factors such as obesity or sleep problems are corrected.
Can I start TRT based on one low test?
Usually no. Symptoms and a repeat appropriately timed testosterone level are important, with additional testing to identify the cause.
Do I need regular blood tests on TRT?
Yes. Testosterone level, haematocrit and appropriate prostate monitoring are important parts of safe treatment.
Can TRT be stopped once it is started?
Sometimes. If low testosterone was mainly functional and the underlying driver improves, treatment can be reassessed. Men with permanent testicular or pituitary failure may need long-term replacement. Do not stop or restart treatment only from symptoms; reassess with the treating doctor.
Related reading
- Low Testosterone in Men: Symptoms and Treatment
- Morning Testosterone Test: Why Timing Matters
- Total Testosterone vs Free Testosterone
- Testosterone and Fertility
- Risks of Testosterone Therapy
- Testosterone and Prostate: Myths and Facts
- Urologist in Latur
References
- European Association of Urology. Guidelines on Sexual and Reproductive Health (2026) https://uroweb.org/guidelines/sexual-and-reproductive-health
- EAU Patient Information. Male Hypogonadism https://patients.uroweb.org/condition/male-hypogonadism
- Endocrine Society. Testosterone Therapy for Hypogonadism Guideline Resources https://www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
- American Urological Association. Evaluation and Management of Testosterone Deficiency https://www.auanet.org/guidelines-and-quality/guidelines/testosterone-deficiency-guideline
- American Urological Association / American Society for Reproductive Medicine. Diagnosis and Treatment of Infertility in Men (2020; amended 2024) https://www.auanet.org/guidelines-and-quality/guidelines/male-infertility
- Endocrine Society. Statement on Testosterone Replacement Therapy. July 16, 2026 https://www.endocrine.org/news-and-advocacy/news-room/2026/statement-on-testosterone-replacement-therapy