What Is TRT? Who Qualifies, How It Is Given and What Monitoring Looks Like

A 52-year-old patient recently brought a phone into his appointment and pressed play. A fitness creator, shirtless and certain, was explaining that every man over 40 is running on empty and that a simple injection fixes it. The patient’s question was short: is any of that true? It is the same question driving a spike in searches for what is TRT, and as of September 2026 the trend has two engines. One is science: the large TRAVERSE cardiovascular safety trial published in 2023, and the regulatory label update in 2025 that followed it. The other is culture: a wave of testimonials that treat a hormone as a lifestyle upgrade.

Both deserve a calm reading. Testosterone replacement therapy is a real medicine for a real diagnosis. It also comes with a diagnostic bar that social media tends to skip, a monitoring routine that is not optional, and evidence that is stronger for some benefits than for others.

This explainer walks through who qualifies, how the treatment is actually given, what the trials show and where the hype runs ahead of the data.

What is TRT, in plain language?

Strip away the acronym and TRT is a replacement, not an enhancement. Testosterone is the principal male sex hormone, made mostly in the testicles under instruction from the pituitary gland at the base of the brain. When the testicles or that signaling system fail and levels fall below the normal range, the condition is called hypogonadism, which simply means underactive gonads. Testosterone replacement therapy supplies the hormone from outside the body so that blood levels return to the range a healthy man of similar age would have.

That word, range, matters. The goal written into endocrinology guidelines is the mid-normal zone, not the ceiling. A clinician is trying to lift someone from clearly deficient to ordinary, which is a different project from pushing a normal man above normal for muscle or mood. The second project is not TRT; it is anabolic steroid use, and the two are often blurred online.

The hormone itself has a long reach. Testosterone supports sperm production, libido and erections, red blood cell production, bone density, muscle mass and fat distribution, body hair and, less predictably, mood and energy. When genuine deficiency is corrected, several of these systems respond. When levels were never truly low, there is far less for the medicine to fix, and the risks remain.

So what is TRT for? Mayo Clinic frames it as treatment for men with hypogonadism confirmed by both symptoms and blood tests, not for the gradual, modest decline that comes with age alone. The National Institutes of Health and most specialty societies draw the same line. Everything that follows, from eligibility to monitoring, flows from that single distinction between a diagnosis and a feeling.

What changed recently: the trial and the label that moved the conversation

Three dated events explain why this topic is live again.

In June 2023, the New England Journal of Medicine published TRAVERSE, the largest randomized safety trial of testosterone ever run. Investigators enrolled 5,246 men aged 45 to 80 who had documented hypogonadism and either existing cardiovascular disease or a high risk of it, then randomized them to a daily testosterone gel or an identical placebo gel. After a mean follow-up of about 33 months, the rate of major adverse cardiac events, a composite of cardiovascular death, heart attack and stroke, was no higher with testosterone than with placebo. The trial met its noninferiority goal. It also recorded more atrial fibrillation (an irregular heart rhythm), more acute kidney injury and more pulmonary embolism (a clot in the lungs) in the testosterone group. The trial is indexed on PubMed and is the backbone of every current safety discussion.

In early 2025, the US Food and Drug Administration finalized class-wide label changes for testosterone products. The boxed warning about cardiovascular risk, added after a 2015 review of observational data, was removed in light of TRAVERSE, while warnings about raised blood pressure were strengthened. Harvard Health has summarized this shift for lay readers.

The third change is less tidy: the normalization of hormone treatment as a consumer product in short-form video. Guideline writers have not relaxed their diagnostic criteria at all. The Endocrine Society’s standing guidance still requires repeated morning blood tests, a search for a cause and a frank conversation about fertility before any prescription. The gap between what the evidence changed (one specific safety question) and what the internet heard (testosterone is safe for everyone) is the reason careful explainers are needed.

Who qualifies for TRT? The two-test rule

Eligibility is a pairing, never a single number. A man qualifies when he has consistent symptoms of testosterone deficiency and unequivocally low blood levels confirmed on at least two separate mornings, ideally fasting, because testosterone peaks before 10 a.m. and dips after meals.

The symptoms clinicians weigh most heavily are the specific ones: low libido, fewer spontaneous erections, loss of body hair, shrinking testicles, infertility and enlarged male breast tissue (gynecomastia). Fatigue, low mood, poor concentration and weight gain count too, but they are nonspecific and overlap with sleep apnea, depression, thyroid disease and simple overwork. Cleveland Clinic’s overview of male hypogonadism lists both groups and notes that the second group alone rarely justifies treatment.

On the laboratory side, the Endocrine Society sets its threshold for low total testosterone at roughly 264 nanograms per deciliter (about 9.2 nanomoles per liter), while the American Urological Association uses 300. These are lab cutoffs for diagnosis, not treatment targets. Men with borderline results, or with conditions that alter the carrier protein SHBG (sex hormone-binding globulin, which holds most testosterone in an inactive form), often need a free testosterone measurement to settle the question.

Several situations rule treatment out or pause it: active prostate or breast cancer, a markedly raised PSA (prostate-specific antigen, a protein measured to screen for prostate problems) that has not been evaluated, a high red blood cell count, untreated severe sleep apnea, uncontrolled heart failure, a recent heart attack or stroke, and a desire to father a child in the near term. The last one surprises people; the mechanism is covered in the fertility section below. Whether an individual meets the bar is a judgment for the prescribing clinician, informed by all of these pieces.

What causes low testosterone in the first place?

Doctors sort hypogonadism by where the fault lies, because the location changes the workup and sometimes the treatment.

Primary hypogonadism means the testicles themselves cannot make enough hormone. Causes include Klinefelter syndrome (a chromosomal condition with an extra X chromosome), undescended testicles in infancy, mumps infection of the testicles, injury, chemotherapy or radiation, and simple aging of the tissue. The pituitary senses the shortfall and shouts louder, so blood tests show high LH and FSH (luteinizing hormone and follicle-stimulating hormone, the two pituitary messengers that drive the testicles) alongside low testosterone.

Secondary hypogonadism means the testicles are healthy but the signal from the brain is weak. Here LH and FSH are low or inappropriately normal. Causes range from pituitary tumors and prior head injury to the commonest culprits of all: obesity, type 2 diabetes, obstructive sleep apnea, chronic opioid use, anabolic steroid use and some glucocorticoid medicines. Severe acute illness also drives levels down temporarily, which is one reason testing during a hospital stay or a bad flu is unreliable.

Then there is the slow slide of age. Population studies suggest total testosterone falls by roughly 1 percent a year after about 40, though the NHS points out that most older men stay inside the normal range and that a sharp midlife drop is unusual. The NHS uses the phrase male menopause only to dismiss it; there is no abrupt hormonal shutdown comparable to ovarian failure.

This classification is why a competent evaluation includes LH, FSH, prolactin (a pituitary hormone that can suppress testosterone when high), and often iron studies or pituitary imaging. Finding a pituitary tumor or sleep apnea changes everything, and a prescription written without that search can mask a condition that needed its own treatment.

How is TRT given? Gels, injections, patches, pellets, oral and nasal forms

Every approved product delivers the same molecule; what differs is how steadily it arrives and how much effort it demands. The prescriber chooses the route, sets the amount and adjusts it from blood tests, so this section describes patterns, not instructions.

Form	How it is used	Pattern of blood levels	Points clinicians weigh
Transdermal gel	Applied daily to skin on shoulders, upper arms or abdomen	Fairly steady day to day	Risk of transfer to partners or children through skin contact; absorption varies
Intramuscular injection	Given at intervals set by the prescriber, in clinic or taught for home use	Peaks after the dose, troughs before the next	Mood and energy can swing; higher red blood cell rise with longer-interval products
Skin patch	Applied nightly	Steady	Skin irritation is common
Subcutaneous pellets	Implanted under the skin by a clinician every few months	Steady, then tails off	Minor procedure; cannot be removed quickly if a problem arises
Nasal gel	Applied inside the nostrils several times daily	Short-lived pulses	Less suppression of fertility hormones; nasal irritation
Oral capsule	Taken with food	Variable	Blood pressure increases reported; older oral forms carried liver concerns

The gel versus injection debate dominates forums, but the honest answer from Mayo Clinic and others is that no route is best for everyone. Injections suit men who dislike daily routines; gels suit men who want flatter levels; pellets suit those who want to think about it rarely. Convenience, side-effect history, fertility plans and how a man’s blood work responds all feed the decision, and switching later is common.

What does TRT do to your body when levels were truly low?

The honest timeline is slower than the testimonials suggest, and it is drawn from men with confirmed deficiency, not from men chasing a boost.

Libido and the frequency of spontaneous erections are usually the first things to shift, often within 3 to 6 weeks, with the full effect settling by about 6 months. Mood and energy can lift over a similar window, though the Testosterone Trials found the vitality improvement too small to reach statistical significance. Erectile function improves modestly; testosterone is a permissive hormone for erections, but blood vessel health matters more, which is why men with diabetes or heart disease often need separate treatment.

Body composition changes over months. Lean mass rises by roughly 1 to 2 kilograms and fat mass falls by a similar amount on average, with strength gains that are real but unspectacular compared with what resistance training alone can produce. Bone density improves over 1 to 2 years, a benefit that matters for men with osteoporosis. Hemoglobin rises, which corrects the mild anemia that often accompanies deficiency; the same effect, overshot, becomes a side effect.

There are physiological changes men notice less. Insulin sensitivity may improve slightly. Body hair returns where it had thinned. The voice does not deepen further in adults. Cognitive benefits, despite enthusiastic claims, were not demonstrated in the cognition arm of the Testosterone Trials.

Men who ask what TRT does to your body often expect a before-and-after photograph. The evidence describes something quieter: a return toward the baseline a man had before his levels fell, arriving over a season or two, provided the diagnosis was correct.

Is TRT a steroid, and is taking TRT illegal?

Chemically, yes: testosterone is an anabolic-androgenic steroid, meaning a steroid hormone that builds tissue (anabolic) and produces male characteristics (androgenic). Every TRT product contains it. So the question people are really asking is whether TRT is the same as what bodybuilders do, and the answer there is no, for three reasons.

The first is dose and target. Replacement aims for the middle of the normal range. Performance use typically pushes levels several times higher, often with multiple compounds stacked together, and the harms scale with that excess: severe suppression of fertility, marked red blood cell increases, liver strain with certain oral agents and well-documented cardiac muscle changes.

The second is indication. TRT requires a diagnosis of hypogonadism documented with repeat blood tests. Anabolic steroid use starts from normal physiology.

The third is supervision. Prescribed testosterone comes with scheduled laboratory monitoring. Nonmedical use usually comes with none.

On legality: in the United States, testosterone has been a Schedule III controlled substance since 1990, meaning it has accepted medical uses but a recognized potential for misuse. Taking it with a valid prescription from a licensed clinician for a diagnosed condition is entirely legal. Possessing or using it without a prescription is not, and products sold without one, including underground or research-labeled vials, fall outside any quality control and are not for sale or self-use. Sports bodies add their own layer: most ban testosterone in competition regardless of a prescription unless a therapeutic use exemption has been granted in advance, and that process is strict.

MedlinePlus puts the practical point simply: testosterone should be used only as directed by the prescriber, and never shared.

What the evidence actually says, graded by strength

Medical evidence comes in tiers. Randomized controlled trials, where men are assigned by chance to treatment or placebo, sit at the top because they cancel out the differences between people who choose treatment and those who do not. Observational data, where researchers watch what happens to men who were already prescribed testosterone, sits lower because sicker or healthier men may be more likely to be treated. Expert consensus sits lower still. Here is how the main TRT claims stack up.

• Sexual function in confirmed hypogonadism: strong. Multiple randomized trials, including the 790-man Testosterone Trials in 2016 and the much larger TRAVERSE cohort, show consistent, moderate improvement in libido and sexual activity.
• Bone density and anemia: strong for the surrogate markers. Randomized data show improved bone density and corrected hemoglobin; whether fractures fall has not been proven.
• Cardiovascular safety: moderate to strong for the specific question answered. TRAVERSE found no excess in heart attack, stroke or cardiovascular death over about 3 years in high-risk men brought to the mid-normal range. It cannot speak to higher doses, longer durations or men without hypogonadism, and the signals for atrial fibrillation, pulmonary embolism and kidney injury remain open questions.
• Mood, energy, cognition: weak to modest. Trial effects are small or absent; the dramatic transformations described online are anecdote.
• Prostate cancer risk: moderate reassurance. Trials show no increase in diagnoses over several years, and observational data are mixed; guidelines still call for PSA monitoring because longer-term certainty is lacking.
• Longevity or preventing disease in men with normal levels: no trial support. This is where enthusiasm most clearly outruns data.

Harvard Health’s summary advice, take a breath before you take the plunge, is a fair reading of this ledger. Benefits are real for the right man. The right man is defined by the diagnosis.

What monitoring looks like on TRT and which blood tests are tracked

A testosterone prescription without a monitoring plan is incomplete, and the plan is more structured than most people expect. The Endocrine Society and urology guidelines describe a similar rhythm: a full baseline, a check after the first few months once levels have stabilized, then roughly every 6 to 12 months for as long as treatment continues.

The baseline covers testosterone itself (two low morning values), a complete blood count, PSA and a digital prostate examination in men over 40 or with risk factors, blood pressure, and often lipids, liver enzymes, a bone density scan if risk is present, and sleep apnea screening. Fertility intentions are documented in writing.

Once treatment starts, three numbers do most of the work.

Testosterone level. Timing depends on the formulation: mid-interval for injections, a few hours after application for gels. The target is mid-normal. Too high invites side effects; too low means the dose or route needs rethinking, and that adjustment belongs to the prescriber.

Hematocrit. This is the proportion of blood made up of red cells. Testosterone stimulates their production, and thicker blood raises clot risk. Guidelines name a ceiling, commonly a hematocrit above 54 percent, at which treatment is paused or changed. Injectable forms raise it more than gels, so men on injections tend to be checked more closely.

PSA. A rise of more than about 1.4 nanograms per milliliter in the first year, or any value that crosses the age-adjusted threshold, triggers a urology referral. This is surveillance, not a cancer diagnosis, and it is why men with a short life expectancy or no interest in prostate evaluation need a frank discussion before starting.

Blood pressure is now on the list for every route after the 2025 label changes. Symptoms are reviewed at every visit too: sleep quality, breast tenderness, swelling in the ankles, mood. If treatment has not helped after an adequate trial at adequate levels, guidelines recommend stopping and reconsidering the diagnosis rather than escalating.

What are the common TRT side effects, and which ones matter most?

Most side effects of testosterone are extensions of what the hormone normally does, which is why they are predictable and why monitoring catches them.

The most frequent clinically meaningful one is erythrocytosis, an excess of red blood cells. In trials and registries it occurs in a meaningful minority of men, more often with injections, and it is the usual reason a dose is lowered, a route is switched or treatment is paused. Left alone, thicker blood increases the risk of clots, which is one plausible thread connecting to the pulmonary embolism signal in TRAVERSE.

Skin effects are common and mostly cosmetic: acne, oiliness, and irritation at a gel or patch site. Gels carry a particular hazard of transfer to a partner or child through skin contact; washing hands and covering the site after application are standard instructions from MedlinePlus.

Breast tenderness or enlarged male breast tissue (gynecomastia) can develop because some testosterone converts to estrogen through an enzyme called aromatase. Fluid retention and ankle swelling occur, which matters more in men with heart failure. Sleep apnea can worsen, which is why untreated severe apnea is a reason to wait.

Shrinking testicles and reduced sperm count are not side effects in the usual sense; they are the direct result of switching off the body’s own production, and they get their own section below.

Mood swings and irritability are reported more with injections, where levels peak and trough. Hair thinning in men genetically prone to male pattern baldness can accelerate. Blood pressure can rise with some oral products.

Then there are the open questions: atrial fibrillation, acute kidney injury and clots were more frequent in the TRAVERSE testosterone arm. These were secondary findings, not the trial’s main question, so they count as signals that need confirmation rather than settled risks. A good prescriber discusses them anyway.

Does TRT shrink your testicles and affect fertility?

Yes to both, and the mechanism is worth understanding because it explains why the effect is expected rather than a sign that something went wrong.

The pituitary gland releases LH and FSH when it senses that testosterone is low. LH tells the testicles to make testosterone; FSH tells them to make sperm. When testosterone arrives from outside the body, the pituitary reads the blood as sufficient and quiets both signals. The testicles, now idle, shrink. The hormone concentration inside the testicle, which is normally far higher than in the bloodstream and is essential for sperm production, collapses. Sperm counts fall, frequently to zero.

How much smaller? Studies describe average reductions in volume in the range of a fifth to a third, often noticeable to the man himself and sometimes to a partner. The tissue also becomes softer. The degree varies with the formulation and the individual, and it tends to be less pronounced with nasal gel, which produces short pulses rather than constant suppression.

Is it reversible? Usually, but slowly. After stopping, sperm production typically recovers over 6 to 18 months, and in a minority of men, particularly those who have used high doses for years or who had borderline fertility to begin with, recovery is incomplete. Testicular size returns gradually as LH resumes.

This is why guidelines are blunt: men who want to father children in the foreseeable future should generally not start standard testosterone replacement. Alternatives that stimulate the body’s own production exist, and some are used off-label for this purpose. The evidence for them is observational and modest, and whether any is appropriate is a decision for the treating clinician, ideally one with fertility expertise. Banking sperm before treatment is a conversation worth having early.

TRT vs HRT: what is the difference, and how do they work?

Both abbreviations describe replacing a sex hormone that the body is no longer producing adequately, and both are prescription-only and monitored. The differences lie in biology and in the strength of the underlying diagnosis.

HRT, hormone replacement therapy, usually refers to estrogen with or without progesterone for women during and after menopause. Menopause is a universal, dated event: the ovaries stop releasing eggs and estrogen production falls sharply over a few years, producing hot flushes, night sweats, vaginal dryness and accelerated bone loss. The diagnosis is clinical and needs no blood test in most women over 45. HRT for symptomatic women has decades of randomized data, including the Women’s Health Initiative, that define benefit and risk by age and time since menopause.

TRT, testosterone replacement therapy, treats hypogonadism in men. There is no male equivalent of menopause. Testosterone declines gradually, most men stay within the normal range, and deficiency must be proven in the laboratory. The randomized evidence base is younger and smaller, anchored by the Testosterone Trials and TRAVERSE.

The hormones also behave differently once replaced. Estrogen does not shut down a woman’s ovaries, which have already stopped. Testosterone actively suppresses a man’s own production and fertility, as the previous section describes.

Monitoring differs too. HRT focuses on breast screening, bleeding patterns and cardiovascular risk. TRT focuses on red blood cell count, PSA and testosterone levels themselves.

Women can also be prescribed testosterone, at much lower levels, for low libido after menopause; that is a separate topic with its own limited evidence and is not what people mean by TRT. The NHS pages on both menopause and the so-called male menopause are useful side-by-side reading for anyone comparing the two.

Can you raise testosterone without TRT?

For a man with secondary hypogonadism driven by a reversible cause, the most effective treatment is often not testosterone at all.

Weight is the clearest example. Fat tissue contains aromatase, which converts testosterone to estrogen, and obesity also dampens the pituitary signal. Weight loss raises testosterone in proportion to the amount lost; studies of men who lose 10 percent or more of body weight through diet, exercise or bariatric surgery show meaningful increases, sometimes back into the normal range. Treating obstructive sleep apnea with positive airway pressure can produce a similar correction, because fragmented sleep suppresses the overnight testosterone surge.

Opioids and some other medicines lower testosterone directly. Reviewing them with the prescriber may matter more than adding a hormone; stopping any medicine is a decision for that prescriber, never a self-adjustment.

Resistance training raises testosterone acutely after a session and supports muscle regardless of hormone level. Chronic overtraining and severe calorie restriction do the opposite. Alcohol in excess suppresses production. Seven to nine hours of sleep is the cheapest hormonal intervention available.

What about supplements? The NIH Office of Dietary Supplements position is sober: zinc and vitamin D correct deficiency-related dips only in men who were deficient in them, and the botanical boosters sold under testosterone-adjacent names have no consistent randomized evidence of raising levels in healthy men. Some have been found adulterated with undeclared drugs. They are not a substitute for diagnosis.

None of this means lifestyle change replaces TRT for a man with primary testicular failure or a pituitary tumor; those men need medical treatment. It does mean that a careful clinician asks about weight, sleep, alcohol and medicines before reaching for a prescription, because fixing the cause can leave the hormone to fix itself.

Common myths about what TRT is and what it does

The viral version of this topic rests on a handful of claims that the evidence does not support. Here are the ones clinicians hear most.

Every man over 40 has low testosterone. Population surveys suggest that clearly low levels affect a minority of middle-aged men, and the NHS notes that most men keep normal levels well into older age. Fatigue is common; deficiency is not.

TRT gives you a bodybuilder’s physique. Replacement to the normal range produces an average lean mass gain of a kilogram or two over months. The transformations attributed to TRT online usually involve doses and compounds that have nothing to do with replacement.

Testosterone causes prostate cancer. This idea dates to 1940s observations that castration shrank advanced prostate cancer. Modern randomized trials over several years show no increase in diagnoses, and the current view is that normal levels do not drive new cancers. Monitoring continues because long-term data are limited, not because the risk is established.

Once you start you can never stop. Men stop for many reasons: side effects, fertility plans, lack of benefit. The body’s own production usually recovers over months, though symptoms of the original deficiency return if it was genuine.

Gels are weaker than injections. Both can achieve the same blood levels; they differ in how steadily. Choice is about convenience and side-effect profile.

TRT is a mood or energy drug. The randomized data on vitality and cognition are modest at best. Men with depression deserve treatment for depression.

A single blood test is enough. Levels vary by time of day, illness and fasting state. Two morning samples are the minimum in every major guideline. A result from a home kit taken at 6 p.m. after a sleepless night tells a clinician very little.

When to see a doctor about low testosterone or during TRT

Two groups of men should book an appointment, and for different reasons.

If you are not on treatment and have persistent low libido, loss of morning erections, shrinking testicles, infertility, enlarged male breast tissue (gynecomastia) or unexplained loss of body hair, ask for an evaluation. The same applies if you have a condition that commonly causes secondary hypogonadism, such as obesity, type 2 diabetes, sleep apnea or long-term opioid use, and you have symptoms on top of it. Bring a list of medicines and supplements. Expect the first step to be two morning blood tests, not a prescription.

If you are already on testosterone, contact the prescribing clinician promptly, or seek emergency care where indicated, for these red flags:

• Chest pain, pressure or sudden shortness of breath, which can signal a heart attack or a clot in the lungs; call emergency services.
• Sudden weakness, facial droop, trouble speaking or vision loss, which are stroke signs; call emergency services.
• A painful, swollen or red calf, which may be a deep vein clot.
• A pounding, racing or irregular heartbeat, given the atrial fibrillation signal in TRAVERSE.
• Severe or worsening snoring, witnessed breathing pauses or daytime sleepiness, suggesting sleep apnea.
• New breast lumps or tenderness, or testicular pain.
• Difficulty passing urine, a weak stream or blood in the urine.
• Headaches, flushing or dizziness alongside rising blood pressure readings.
• Marked mood change, aggression or low mood.
• Missed monitoring blood tests for more than a year.

Do not adjust, skip or stop testosterone on your own, and do not add supplements or other hormones without telling the prescriber. If a partner or child develops unexplained acne, body hair or behavioral change while you use a gel, raise it immediately; skin transfer is treatable once recognized. Every decision about continuing, changing or stopping treatment belongs to the clinician who knows your blood work and your history.

Frequently asked questions

What is TRT, in one sentence?

TRT is testosterone replacement therapy, a prescription treatment that restores blood testosterone to the normal range in men diagnosed with hypogonadism, meaning their testicles or the brain signals that drive them no longer produce enough of the hormone. It is given as gels, injections, patches, pellets, nasal or oral products and is monitored with regular blood tests for testosterone, red blood cells and PSA.

Is TRT a steroid?

Chemically, yes: testosterone is an anabolic-androgenic steroid hormone. The distinction that matters is between replacement, which brings a deficient man back to the mid-normal range under medical supervision, and performance use, which pushes a man with normal levels several times above normal, often with several compounds at once. The latter carries far greater risks to fertility, blood thickness and the heart, and is not what clinicians mean by TRT.

Is taking TRT illegal?

No, when it is prescribed by a licensed clinician for a diagnosed condition. In the United States testosterone is a Schedule III controlled substance, so possessing or using it without a valid prescription is illegal, and products sold outside the regulated supply have no quality control and are not for self-use. Competitive athletes also need an approved therapeutic use exemption in advance, since most sports bodies ban testosterone otherwise.

What does TRT do to your body?

In men with confirmed deficiency, TRT typically improves libido and spontaneous erections within weeks, modestly increases lean mass and reduces fat over months, raises hemoglobin, and improves bone density over 1 to 2 years. It also suppresses the body’s own testosterone and sperm production, can thicken the blood, and may cause acne, fluid retention or breast tenderness. Effects on energy, mood and cognition are small in randomized trials.

How small do testicles get on TRT?

Studies report average testicular volume reductions of roughly a fifth to a third, often noticeable to the man and sometimes to a partner, along with softer texture. The shrinkage happens because outside testosterone quiets the pituitary hormones LH and FSH that keep the testicles active. It is usually reversible after stopping, but recovery takes months, and nasal formulations appear to cause less suppression than other routes.

What are the most common TRT side effects?

The most clinically important is an excess of red blood cells, which thickens the blood and is the usual reason treatment is adjusted. Others include acne, skin irritation at application sites, fluid retention, breast tenderness or enlarged male breast tissue (gynecomastia), worsened sleep apnea, accelerated male pattern hair loss, reduced fertility and smaller testicles. The TRAVERSE trial also noted more atrial fibrillation, clots and kidney injury, signals that still need confirmation.

What blood tests are done for TRT monitoring?

Before treatment: two morning testosterone levels, LH and FSH, a complete blood count, PSA, often prolactin, lipids and liver enzymes, plus blood pressure and a prostate examination in older men. During treatment: testosterone at the right time for the formulation, hematocrit, and PSA, usually checked a few months after starting and then every 6 to 12 months. Blood pressure is now reviewed at every visit for all routes.

What is the difference between TRT vs HRT?

HRT usually means estrogen-based therapy for women after menopause, a universal and clinically obvious event with decades of trial data. TRT treats male hypogonadism, which must be proven with repeat blood tests because testosterone declines gradually and most men stay in the normal range. Testosterone also actively suppresses a man’s own hormone and sperm production, which estrogen does not do to already-inactive ovaries.

Does TRT cause prostate cancer?

Current randomized trials lasting several years show no increase in prostate cancer diagnoses among men treated to the normal range, and the old assumption that testosterone fuels new cancers is not supported by modern data. Guidelines still require PSA monitoring and exclude men with active prostate cancer, because long-term certainty is limited and testosterone can accelerate an existing cancer. A rising PSA on treatment prompts urology review, not panic.

Can you stop TRT once you start?

Yes, and men stop for many reasons: side effects, a wish to father children, or lack of benefit after an adequate trial. The body’s own production usually resumes over several months, though symptoms of the original deficiency return if the diagnosis was genuine. Stopping should always be planned with the prescribing clinician, who may taper or switch rather than halt abruptly depending on the formulation and the reason.

References

• Cleveland Clinic: Low Testosterone (Male Hypogonadism)
• MedlinePlus: Could you have low testosterone?
• NHS: The 'male menopause'

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.