Low Testosterone Treatment in London: Diagnosis, TRT and Fertility
- Prof Fabio Castiglione, MD, PhD, FECSM, FEBU
- 2 days ago
- 5 min read
Key point: testosterone replacement therapy (TRT) is appropriate only when compatible symptoms occur together with consistently low testosterone confirmed by correctly timed blood tests. Tiredness or a single low result is not enough. The cause, cardiovascular and prostate health, haematocrit, medicines, sleep and future fertility should be reviewed before treatment.
What is male hypogonadism?
Male hypogonadism means that the testes do not produce enough testosterone for normal function. The problem may originate in the testes (primary hypogonadism) or in the pituitary–hypothalamic signals that control them (secondary hypogonadism). Some men have functional suppression associated with obesity, chronic illness, poor sleep, medicines or previous anabolic-steroid use.
Testosterone levels commonly vary with time of day, food intake, sleep and acute illness. Ageing alone does not justify TRT, and treatment should not be used as a general anti-ageing, energy or bodybuilding intervention in men whose testosterone is normal.
Which symptoms are most relevant?
Sexual symptoms are usually the most specific. These can include reduced sexual desire, fewer spontaneous or morning erections and erectile difficulty. Other possible features include reduced energy, low mood, decreased muscle strength, reduced body hair, hot flushes, infertility or low bone density. Each can also have other causes, so symptoms must be interpreted with blood results and medical history.
If changes in morning erections are your main concern, read No Morning Erections: When Should You Be Concerned?.
How is low testosterone diagnosed?
Current European Association of Urology guidance recommends diagnosis only in symptomatic men and measurement of total testosterone between 07:00 and 10:00, fasting, using a reliable laboratory assay. A low result should be repeated on a separate morning before TRT is started.
The EAU uses total testosterone below 12 nmol/L as a practical diagnostic threshold for late-onset hypogonadism, but the result is not interpreted in isolation. Sex hormone-binding globulin (SHBG) and calculated free testosterone may help when total testosterone and symptoms do not match, or when conditions that alter SHBG are present.
Luteinising hormone (LH) and follicle-stimulating hormone (FSH) help distinguish primary from secondary hypogonadism. Prolactin and other investigations may be required when secondary causes, low desire or pituitary disease are suspected. Severe secondary hypogonadism or symptoms such as visual-field change or new headaches may require pituitary imaging.
What should be assessed before TRT?
A safe assessment reviews:
• symptoms, examination findings and two correctly timed testosterone results;
• LH, FSH, SHBG/free testosterone and prolactin when indicated;
• weight, waist, blood pressure, diabetes risk, lipids, sleep and mental health;
• prescribed medicines, opioids, alcohol, supplements and anabolic-steroid exposure;
• full blood count and haematocrit;
• prostate assessment and PSA where appropriate for age and individual risk;
• current or future desire for children.
Reversible contributors—such as obesity, poor sleep, uncontrolled diabetes, acute illness or a relevant medicine—may need attention before or alongside hormone treatment. Treating the cause can sometimes improve testosterone without TRT.
Fertility: the essential warning before testosterone
External testosterone suppresses pituitary gonadotrophins and can markedly reduce or stop sperm production. It should not be prescribed to treat male infertility and is contraindicated when a man is actively trying to conceive. Recovery after stopping can take months and is not identical for everyone.
Tell your clinician about plans for children before any first prescription—even if fertility is a future rather than immediate goal. Men with secondary hypogonadism who want fertility may require specialist investigation and, in selected cases, gonadotrophin-based treatment instead of testosterone. NICE 2026 recommends gonadotrophin therapy for hypogonadotropic hypogonadism and advises against androgens for semen abnormalities.
For more context, see Understanding the Importance of Male Fertility Assessment.
Who may benefit from testosterone replacement?
TRT may be considered for a man with clinically relevant symptoms, consistently low morning testosterone and no contraindication, after causes and alternatives have been reviewed. Potential benefits can include improved sexual desire and milder erectile symptoms, body composition, bone density and some mood symptoms. The degree and timing of benefit vary, and treatment does not guarantee restoration of erections, energy or fertility.
When erectile dysfunction is the main problem, vascular risk, medicines, penile factors and psychological contributors must also be assessed. Read Urologist or Andrologist for Erectile Dysfunction in London?.
When is TRT unsuitable or requires specialist caution?
Important contraindications include active prostate cancer, active male breast cancer, a desire for fertility, haematocrit at or above 54%, and uncontrolled or poorly controlled heart failure. Severe lower urinary tract symptoms, high baseline haematocrit, a history or risk of venous thromboembolism, cardiovascular disease and previous prostate-cancer treatment require careful individual review.
A high PSA or abnormal prostate examination should be investigated before treatment. Evidence does not show that correctly prescribed TRT causes prostate cancer, but long-term data have limitations and prostate monitoring should be risk-based and shared with the patient.
TRT options used in the UK
Transdermal gels are applied daily and allow relatively straightforward dose adjustment. Transfer to another person through skin contact must be prevented by following product instructions, washing hands and covering the application site once dry.
Injections can be short-acting or long-acting depending on the preparation. Dosing intervals, peaks and troughs, convenience and risk of increased haematocrit should be discussed.
Other preparations may be available in selected settings. The best choice depends on diagnosis, health risks, preference, cost, monitoring and whether rapid treatment withdrawal would be desirable. Buying testosterone online or using non-prescribed anabolic steroids is unsafe.
How is treatment monitored?
Monitoring checks whether symptoms improve and whether testosterone remains in an appropriate range without adverse effects. EAU guidance recommends testosterone and haematocrit at three, six and twelve months after starting, then annually; higher-risk men may need more frequent checks. A haematocrit above 54% requires treatment adjustment or withdrawal and clinical management.
Follow-up may also include blood pressure, weight, treatment application or injection timing, adverse effects, PSA and prostate review according to age and risk, and evaluation of sleep apnoea or cardiovascular symptoms. If symptoms do not improve despite adequate levels, the diagnosis and benefit of continuing TRT should be reconsidered.
Frequently asked questions
Is one low testosterone result enough to start TRT?
No. Diagnosis normally requires compatible symptoms and low fasting morning total testosterone on at least two separate occasions, followed by assessment of the cause.
Can TRT improve erectile dysfunction?
It may improve libido and milder erectile dysfunction in men with confirmed hypogonadism. It is not a universal ED treatment, and other vascular, medication-related, penile or psychological factors may need separate management.
Does TRT make a man infertile?
It can substantially suppress sperm production and may cause azoospermia. Men who want children should not start external testosterone without specialist fertility advice.
Can weight loss or better sleep raise testosterone?
They may help when testosterone suppression is associated with obesity, sleep disruption or related health problems. Lifestyle treatment is important but does not replace hormone replacement in every case of organic hypogonadism.
Is testosterone therapy lifelong?
It depends on the cause. Permanent testicular or pituitary disease may require long-term replacement; reversible functional causes may allow reassessment. Treatment should be reviewed rather than automatically renewed.
Low testosterone consultation in London
A specialist consultation can confirm whether symptoms and laboratory findings fit hypogonadism, investigate the cause, protect fertility and build a monitoring plan. Book a confidential appointment.
About the author
Prof Fabio Castiglione, MD, PhD, FECSM, FEBU, Urologist (ITA). Consultant Urologist and Andrologist — King’s College Hospital NHS Foundation Trust; Hon. Reader, King’s College London, UK; Academic Lead of Urology; GMC 7542824; Director and Founder of Holistic Andrology.
Research profiles: ORCID 0000-0001-8046-1963 · PubMed publications · King’s College Hospital consultant profile.
Medical sources
This article is for general education and does not replace individual medical assessment or a prescription.
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