Testosterone Replacement Therapy (TRT)

Testosterone Replacement Therapy restores testosterone to the normal range in people with clinically confirmed androgen deficiency. It is a registered, well-studied medicine — but it works by switching off the body's own production, the symptom benefits in trials were more selective than the marketing suggests, and the cardiovascular safety question took a decade and a dedicated trial to settle only partly.

What TRT is

Testosterone Replacement Therapy is the long-term administration of testosterone to someone whose own production is inadequate, aiming to return blood levels — and the symptoms that follow from them — to the normal adult range. The clinical target is normality, not maximisation, and that changes how the treatment is prescribed, monitored and judged.

Several products are ARTG-registered in Australia — injectable esters, and transdermal gels and creams — all Schedule 4 (prescription-only). Around them sits a cluster of adjunct medicines, some registered and some compounded; knowing which of yours is which is one of the most useful things a patient can understand, and our compounded vs registered explainer covers the difference.

How it works — and what it switches off

Testosterone is not produced autonomously. It is the output of a three-tier control loop, the hypothalamic–pituitary–gonadal (HPG) axis, and that loop explains most of what TRT does — including the parts people find surprising.

The loop. The hypothalamus releases gonadotropin-releasing hormone in pulses, instructing the anterior pituitary to release two gonadotropins: luteinising hormone (LH) and follicle-stimulating hormone (FSH). LH acts on the Leydig cells of the testes, which convert cholesterol into testosterone. FSH acts on the Sertoli cells, which — together with a very high local concentration of testosterone inside the testis — support sperm production. Circulating testosterone, and the oestradiol it is converted into by aromatase, then travel back to the hypothalamus and pituitary and suppress GnRH, LH and FSH. Classical negative feedback: the more testosterone in the blood, the fewer instructions to make more.

What replacement does to that loop. Administered testosterone is indistinguishable to those sensors from testosterone you made yourself, so it suppresses LH and FSH. The Leydig cells stop being told to work and testicular volume commonly falls. But the consequence that matters most is inside the testis: intratesticular testosterone runs far above blood levels, and spermatogenesis depends on that local concentration, not the blood level. Replacing testosterone in the blood does not replace it in the testis. This is why TRT suppresses fertility, often profoundly — and why the same mechanism is studied as a male contraceptive.

That loop is also why a proper workup measures LH and FSH alongside testosterone. Low testosterone with high gonadotropins points to a testicular problem (primary hypogonadism): the pituitary is shouting and nothing is answering. Low testosterone with low or inappropriately normal gonadotropins points upstream to the hypothalamus or pituitary (secondary hypogonadism) — a different diagnosis with different causes, including pituitary tumours, opioids, obesity and sleep apnoea. A clinic that does not measure gonadotropins cannot tell the two apart.

What the human evidence actually shows

The symptom benefits are real but selective. The Testosterone Trials, a coordinated set of placebo-controlled trials in older men with unequivocally low levels, found consistent improvement in sexual function — libido, sexual activity and erectile function. Effects on vitality and energy were small and did not reach the threshold investigators had pre-set as clinically meaningful on the primary measure. Mood effects were modest, walking distance improved only marginally, and the bone density and anaemia sub-studies were positive.

That is a more nuanced picture than "testosterone fixes fatigue". If exhaustion rather than sexual symptoms is your dominant complaint, the evidence supports a smaller benefit than most clinic marketing implies, and the placebo response here is large. Body composition changes reliably — lean mass rises, fat mass falls — but strength and function gains are more modest.

The cardiovascular story is the important one. An earlier trial in older, frail men was stopped early for excess cardiovascular events, observational data through the 2010s conflicted, and regulators added cautionary labelling. The question was addressed directly only by TRAVERSE, a large randomised placebo-controlled safety trial in men with hypogonadism who already had cardiovascular disease or were at high risk. Its finding: testosterone was non-inferior to placebo for major adverse cardiac events.

That is genuinely reassuring, and it is the single most important piece of TRT safety evidence. But read the rest. TRAVERSE also found higher rates of pulmonary embolism, atrial fibrillation and acute kidney injury in the testosterone group. It tested a transdermal preparation, over a few years, in men treated to the normal range. It says nothing about decades of exposure, or about levels pushed above normal — which is exactly what "optimisation" clinics propose. Separately, a cardiovascular imaging sub-study within the Testosterone Trials found a greater increase in non-calcified coronary plaque volume in treated men than in those on placebo; its significance is unresolved, but it belongs on the table rather than omitted.

On age-related decline. Testosterone falls gradually with age in most men, and Australian endocrinology guidance has been consistently cautious about treating that fall as a disease in itself, absent an identified cause. That is the difference between replacing a hormone in someone with a diagnosis and prescribing one to someone who is simply older.

Regulatory positions, PBS criteria and the reading of the cardiovascular data have all shifted over the past decade. Treat anything you read about TRT — this page included — as a starting point to confirm with your practitioner against current sources.

Regulatory status in Australia

Testosterone is a Schedule 4 prescription-only medicine, and prescribing it lawfully requires a registered practitioner and a genuine assessment. ARTG registration means the TGA has evaluated a product's quality, safety and efficacy, and that an approved Product Information document exists setting out indications, contraindications and warnings — precisely what a compounded preparation does not have.

Adjuncts vary. Human chorionic gonadotropin and anastrozole are registered here, though use alongside testosterone may fall outside their approved indications. Enclomiphene and gonadorelin are typically compounded — lawful for an individual patient, but not TGA-evaluated, with batch consistency resting on the pharmacy's own systems.

PBS subsidy is restricted, deliberately. Testosterone is subsidised only for established androgen deficiency attributable to an identified pathological cause, confirmed on repeat morning blood testing, with additional authority requirements for older men that generally involve a specialist confirming the diagnosis. Age-related decline without an identified cause does not meet the criteria. These rules have been revised repeatedly — confirm the current position rather than relying on any summary, including this one.

Importing testosterone without a prescription is not lawful, and product from overseas websites or "research" suppliers carries no assurance of identity, sterility or content. Testosterone is also on the World Anti-Doping Agency prohibited list.

What a proper diagnosis looks like here

• Specific symptoms — reduced libido, erectile dysfunction, loss of morning erections, small testes, gynaecomastia, loss of muscle bulk. Fatigue and low mood alone are weak signals with many other causes.
• Repeat morning blood samples, fasting, on separate days, because testosterone varies through the day, day to day, and falls during acute illness.
• LH and FSH to localise the problem, plus SHBG (which changes how a total testosterone result should be read), prolactin, iron studies and a full blood count — with specialist referral or imaging where a pituitary cause is suspected.
• A search for reversible causes — obesity, obstructive sleep apnoea, opioids, corticosteroids, excess alcohol, poorly controlled diabetes, thyroid disease. Functional suppression from obesity or sleep apnoea often improves when the underlying problem is treated, which is why weight management and hormone assessment increasingly overlap.
• A fertility conversation before the first prescription, not after.

A provider who prescribes without gonadotropins, without repeat testing, or without asking about fertility has not done an adequate workup. Who qualifies for TRT in Australia covers the thresholds; how to choose a peptide or TRT clinic covers what a credible service looks like in practice.

Who it is for — and who it is not for

TRT is for people with confirmed hypogonadism from an identified cause — testicular injury or failure, Klinefelter syndrome, pituitary disease, and certain genetic or treatment-related causes. It is also used in gender-affirming care, which follows its own protocols.

A practitioner would decline, or involve a specialist, where there is known or suspected prostate or male breast cancer, an unexplained raised PSA, a high haematocrit, untreated severe sleep apnoea, severe heart failure, a history of venous thromboembolism, or a near-term plan to conceive. Transdermal preparations can also transfer to a partner or child through skin contact. The group most often inappropriately offered TRT is men with borderline levels and non-specific symptoms who have not been investigated for anything else.

Risks and considerations

Erythrocytosis — a rise in red cell count and haematocrit — is the most common clinically significant effect, more pronounced with injectable than transdermal preparations. It raises blood viscosity, is checked at every review, and may require changing preparation or venesection.

Fertility suppression is expected, not a surprise. Recovery after stopping is usual but not universal and can take many months to well over a year.

Prostate. Current evidence does not show that TRT causes prostate cancer, but it can accelerate one already present, so PSA and prostate assessment form part of standard monitoring. Other effects include acne and oily skin, fluid retention, gynaecomastia from aromatisation to oestradiol, mood changes and irritability, worsening sleep apnoea, and injection-site or skin reactions. The TRAVERSE signals belong here too. And supraphysiological dosing changes the risk profile entirely — a clinic proposing levels above the normal range has left the evidence base this page describes.

Cost, monitoring and what stopping looks like

For most men with true hypogonadism this is ongoing, usually permanent therapy — symptoms return when it stops. Monitoring is the treatment, not an add-on: expect baseline pathology, review during the first months as levels stabilise, then regular bloods covering testosterone, full blood count and haematocrit, PSA where age-appropriate, lipids and liver function.

Cost. Meet the PBS criteria and the medicine is comparatively inexpensive. Otherwise you pay a private script price plus consultations plus recurring pathology, and telehealth services frequently add a membership fee. Ask for the total annual cost in writing before you start — telehealth vs in-person hormone therapy covers the trade-offs.

Stopping. The HPG axis usually restarts after suppression, but recovery is gradual and some men have a prolonged stretch of symptomatic low testosterone in between — discuss that before the first prescription.

What to ask a doctor

• What is my diagnosis, and what caused it — primary or secondary hypogonadism?
• Will you confirm my levels on repeat morning blood tests, and measure LH and FSH?
• What reversible causes have you ruled out first, and which of my medicines are compounded rather than TGA-registered?
• What will this do to my fertility, and should I store sperm first?
• What monitoring will I have, how often, and which markers?
• Do I meet the PBS criteria? If not, what is the full annual cost including pathology?
• Is this lifelong, what happens if I stop, and can I verify the prescriber on the AHPRA register?

FAQ

Is TRT the same as steroids for performance? No, though the molecule can be. TRT restores a diagnosed, deficient person to the normal range under monitoring. Performance use pushes levels above normal, with a materially different risk profile — and the safety evidence on this page, TRAVERSE included, applies to replacement, not supraphysiological use.

My testosterone is "low normal" and I'm exhausted. Is TRT the answer? Possibly not. Energy and fatigue are the weakest part of the TRT evidence base, and fatigue has a long list of common, treatable causes — iron deficiency, thyroid disease, sleep apnoea, depression, medication effects. Obesity and sleep apnoea also suppress the HPG axis directly, and levels often improve when they are treated, which is why some people are better served discussing semaglutide or tirzepatide with their doctor than hormone replacement.

Where should I start? With a diagnosis, not a product. See a GP or endocrinologist and understand what is actually causing your symptoms. If replacement is genuinely indicated, you will be far better placed to judge a provider — and can then compare doctor-supervised hormone clinics, take the questions worth asking into that consultation, and check the prescriber's registration.