今日のテストステロン療法：生殖能力、前立腺がん、心臓の健康について解説

最終更新日： 8月 29, 2026

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Testosterone therapy is one of the most talked-about — and most misunderstood — topics in men’s health. Should a young man take it if he wants children? Is it dangerous for someone who has had prostate cancer? Will it cause a heart attack? These are real questions I hear every week, and the answers have shifted considerably in recent years.

In May 2026 I had the privilege of shadowing モーヒット・ケラ教授 at the 米国泌尿器科学会（AUA）2026年総会 in Washington, DC. One of the most memorable sessions was a series of real-world testosterone case discussions. Here are three of them in plain language, because they capture how the field is replacing old fears with case-by-case judgement — which is not the same as replacing them with new certainties.

Case 1: The Young Man Who Wanted Both Energy and a Baby

The first case involved a man in his late thirties, newly married and trying to start a family. He had severe erectile dysfunction, low energy and very low libido. His blood tests showed strikingly low testosterone, and he had obesity, diabetes and sleep apnoea — three conditions that commonly drag testosterone down, and which are covered in the link between weight and testosterone.

Here is the crucial twist: he badly wanted to feel better, and he was actively trying to conceive.

Why Standard Testosterone Was Off the Table

It seems logical that a man with low testosterone should be given testosterone. But for a man trying to have children, standard testosterone therapy is the wrong tool. When testosterone comes from outside, the brain senses there is plenty and switches off the signals that keep the testicles working. Sperm production stops with it — in many men, all the way to a count of zero. It usually recovers after stopping, over months rather than weeks, and not in every man. This is set out further on the male fertility service page.

The Alternative Approach

Instead of giving testosterone directly, we use medication that encourages the body to make its own, keeping sperm production intact. The common starting point is clomiphene, a tablet that nudges the brain into sending stronger signals to the testicles.

The case revealed a useful real-world lesson. Clomiphene raised the patient’s testosterone beautifully on paper, but he still did not feel much better — energy and libido stayed low. As Dr. Larry Lipshultz explained on the panel, this is common: clomiphene is good at improving the number, and a meaningful proportion of men do not get the symptom relief they hoped for. Where that happens, hCG injections are often the next step: because this patient’s testicles had responded, they were clearly functional, and hCG mimics the body’s own signal to them directly, frequently helping both symptoms and fertility.

An aromatase inhibitor is sometimes added where testosterone is being converted to oestrogen faster than is useful. Clomiphene, hCG and aromatase inhibitors are all prescribed here. Their common feature is that they work with the testicles rather than replacing them — and that they need the same monitoring as any hormonal treatment, not less.

The takeaway: for younger men who want to preserve fertility there are real alternatives to standard testosterone — and the goal is not a better number, it is a man who actually feels better. If the number improves and he does not, the treatment has not worked.

Case 2: Testosterone After Prostate Cancer — Revisiting an Old Fear

The second case tackled one of the most emotionally charged questions in urology: is it safe to give testosterone to a man who has had prostate cancer?

The patient was a man in his late fifties, successfully treated for high-risk prostate cancer a few years earlier. His cancer was in remission, but he was suffering badly — crushing fatigue, very low libido, depression and erectile dysfunction, with extremely low testosterone and a collapsed quality of life.

Pouring Petrol on a Fire? The Picture Has Changed

For decades, doctors believed that giving testosterone to a prostate cancer survivor was like pouring petrol on a fire. That absolute position has softened, largely because of the saturation model: prostate tissue appears to respond to testosterone only up to a point, like a sponge that can hold only so much water. Once the receptors are saturated — which happens at a relatively low level — adding more testosterone does not appear to drive extra growth.

Two honest qualifications belong with that. The saturation model is a well-supported explanation rather than a proven law, and the clinical evidence behind treating survivors comes largely from observational series rather than large randomised trials — in part because TRAVERSE and the earlier T-Trials both excluded men with a prostate cancer history altogether, so the largest datasets in the field say nothing about exactly this question. And this is not a routine treatment: it is a decision made in selected men, with full counselling about what remains unknown, and with the oncology or radiotherapy team that treated the cancer rather than by a urologist alone. Men with untreated prostate cancer, or on active surveillance, are a different conversation again. This site covers the saturation model in more depth separately.

Reading the Warning Signs Correctly

After starting testosterone the patient’s PSA ticked up slightly, causing understandable alarm for both him and his cancer doctor. The experts were unsurprised: a small early rise is expected as testosterone climbs from a very low level and the remaining normal prostate tissue wakes up. It does いいえ by itself mean the cancer is back.

His symptoms improved substantially and his PSA settled. About a year later it jumped much higher — far beyond what the saturation effect could explain. That was a genuine red flag, and advanced imaging confirmed recurrence in a nearby lymph node.

The lesson drawn by the panel was that the testosterone did not cause the recurrence: given his original high-risk disease, microscopic cancer was already there, and the therapy revealed it rather than created it. That is a reasonable interpretation of a single case rather than something a single case can prove — which is precisely why this treatment belongs with close PSA surveillance and a team that will act on a change, not with a prescription and a follow-up in a year.

Case 3: Protecting the Heart — and a Side Effect That Needs Watching

The final case is one almost every doctor sees: an older man with low testosterone そして a complicated heart history. He was in his early sixties with low energy, low libido and ED, plus high blood pressure, obesity, coronary artery disease and previous open-heart bypass surgery. His father had died young of a heart attack.

He asked the question on every cardiac patient’s mind: will testosterone increase my risk of another heart attack?

What TRAVERSE Actually Showed — and How Strong Each Finding Is

For years the medical world was split, largely because of flawed older studies. The TRAVERSE trial randomised 5,246 men aged 45 to 80 who already had heart disease or high cardiovascular risk, and followed them for a mean of 33 months. Its main finding was reassuring: testosterone therapy did いいえ increase major adverse cardiac events — heart attack, stroke or cardiovascular death — compared with placebo.

That is the headline, and it is genuinely important. It is also not the whole result — and the rest is easy to report badly in either direction. An earlier version of this article listed the remaining signals together without saying how strong each one was. Separated properly:

• Statistically significant. 赤血球増加症 — thickened blood — was by a wide margin the clearest adverse effect in the trial. It is the subject of the rest of this case, and it is why the blood tests are not optional. The fracture subtrial also found a significant increase of roughly 43% in clinical fractures, which is why testosterone is not prescribed to protect bone even though it improves bone density on a scan.
• Numerically higher, but not statistically significant. Atrial fibrillation, pulmonary embolism and acute kidney injury each occurred somewhat more often on testosterone, but none of those differences reached statistical significance. They should not be described as established harms — and equally, a trial this size failing to reach significance is not proof of no effect, so a previous clot, a clotting disorder or a known arrhythmia is still worth raising before starting.

Separately from any of that, some symptoms are never for the next appointment:

• Chest pain or sudden breathlessness
• Pain or swelling in one calf
• A sudden severe headache with weakness or difficulty speaking
• New palpitations or an irregular heartbeat that persists

Any of these means going to hospital and telling the team you are on testosterone. In Thailand, call 1669. These are symptoms anyone should act on regardless of medication; listing them here is prudence rather than a claim that testosterone caused them.

The panel also debated the decision itself. Some preferred a cautious approach — weight loss, stopping smoking, lifestyle first, since his testosterone was only borderline low. Others pointed out that low testosterone left untreated is itself associated with worse cardiac and metabolic health. Worth being precise there: an association is not proof that treating it protects the heart, and TRAVERSE did not show a cardiovascular benefit. It showed the absence of the harm people feared. The full account is in testosterone and the heart.

The BPH Question

The patient also worried that testosterone would worsen the urinary symptoms of an enlarged prostate, a fear reinforced by cautious product labelling. The evidence does not support it: restoring testosterone to normal levels has not been shown to worsen urinary symptoms, and some men report mild improvement. That said, urinary symptoms are still worth reviewing during treatment rather than assumed to be unrelated — particularly in a man who already struggles to empty his bladder.

Thickened Blood — the Side Effect That Most Often Forces a Change

The patient started weekly testosterone injections and felt transformed — more energy, sharper thinking, a much better sex life. Then a routine safety blood test showed his blood was thickening: erythrocytosis, too many red blood cells. In a man with multiple bypasses, thicker blood that clots more readily is a genuine concern.

It is worth naming what this is: of everything TRAVERSE measured, this is the adverse effect the trial demonstrated most convincingly. It is not a footnote to the cardiovascular discussion — it is the finding with the strongest evidence behind it.

Dr. Lipshultz shared a practical approach. The large peaks produced by standard weekly injections appear to be a major trigger for red cell overproduction, so rather than abandoning a therapy that had transformed the patient’s life, the delivery was changed: small, frequent subcutaneous doses using a fine insulin-style needle a couple of times a week, keeping the level steady instead of spiking. In his experience this often brings the blood count back down while keeping the benefits.

Two caveats worth stating plainly. That is expert practice and clinical experience rather than trial evidence, so it is a reasonable thing to try rather than a guaranteed fix. And it is not the only lever: lowering the dose, spacing injections, treating an untreated sleep apnoea that is contributing, donating blood or, where the haematocrit stays high, stopping therapy are all part of the same conversation. What is not optional is the blood test. Haematocrit is checked before starting and regularly afterwards, and it is the number that most often dictates a change of plan — which is also why testosterone bought without monitoring is a genuinely bad idea.

The Big Picture: From Blanket Rules to Individual Judgement

What struck me about these discussions was how far the field has moved away from rigid, fear-based rules — and, equally, how carefully the experts hedged. The confident bit is that old absolute prohibitions have not held up. The honest bit is that what replaced them is monitoring and judgement, not a new set of guarantees.

All three cases share one theme: the right answer depends on the individual, not on a blanket rule — and in all three, what made the treatment safe was the follow-up rather than the prescription. A TRT consultation at Bangkok Hospital is built around that same case-by-case assessment. The practical side of injection technique is covered in the subcutaneous injection guide.

If you are experiencing symptoms of low testosterone — low energy, low libido, mood changes or erectile dysfunction — and would like a full evaluation, Dr. Soarawee Weerasopone consults at バンコク病院本部 そしてチョンブリー県のサミティベート・シーラチャ病院にて 088-022-1445.

バンコク病院の遠隔医療は、来院が困難な患者様（海外からの患者様を含みます）を対象にご利用いただけます。泌尿器科宛てに事前にメールでご手配ください。 bhquro@bdms.co.th. It suits reviewing blood results and planning follow-up; the initial assessment needs an in-person visit and morning blood tests. Samitivej Sriracha is in-person only. Enquiries about cost are answered by the hospital rather than through this website.

お客様からよくいただくご質問

Can I take testosterone therapy if I want to have children?

Standard testosterone therapy is not appropriate for men actively trying to conceive, because it signals the brain to shut down natural sperm production and in many men the count falls to zero. It usually recovers after stopping, over months rather than weeks, and not in every man. Fertility-preserving alternatives such as clomiphene, hCG injections and, where appropriate, an aromatase inhibitor stimulate the body to produce its own testosterone while protecting sperm production. All three are prescribed here.

Is testosterone therapy safe after prostate cancer?

The old absolute prohibition has softened. Under the saturation model, prostate tissue appears to respond to testosterone only up to a relatively low threshold, beyond which more testosterone does not appear to drive further growth. For carefully selected survivors with low testosterone and severe symptoms it can be a reasonable option for symptom relief. Two things matter: the evidence comes largely from observational series rather than randomised trials — TRAVERSE and the T-Trials both excluded men with a prostate cancer history — and the decision is made together with the team that treated the cancer, with close PSA surveillance. Men with untreated cancer or on active surveillance are a separate discussion.

Does testosterone therapy increase the risk of heart attack?

The TRAVERSE trial, designed specifically to test cardiovascular safety in men with existing heart disease or high risk, found no increase in major adverse cardiac events — heart attack, stroke or cardiovascular death — compared with placebo. It also did not show a cardiovascular benefit: untreated low testosterone is associated with worse cardiac and metabolic health, but association is not proof that treatment protects the heart.

Which TRAVERSE findings were statistically significant?

Two. Erythrocytosis, a rise in red cell count, was by far the clearest, which is why haematocrit monitoring is not optional. Clinical fractures rose significantly, by roughly 43%, in the fracture subtrial, which is why testosterone is not prescribed to protect bone. Atrial fibrillation, pulmonary embolism and acute kidney injury were each numerically higher on testosterone but did not reach statistical significance, and should not be described as established harms. An earlier version of this page listed those three without that qualification.

What symptoms on testosterone therapy need urgent attention?

Chest pain or sudden breathlessness, pain or swelling in one calf, a sudden severe headache with weakness or difficulty speaking, or persistent new palpitations. Go to hospital and tell the team you are on testosterone; in Thailand, call 1669. These are symptoms anyone should act on regardless of what they take — listing them here is prudence, not a claim that testosterone caused them.

Does testosterone therapy make an enlarged prostate (BPH) worse?

Current evidence does not show that restoring testosterone to normal levels worsens urinary symptoms, and some men report mild improvement. It remains worth reviewing urinary symptoms during treatment rather than assuming they are unrelated, particularly in a man who already has difficulty emptying his bladder.

Why does testosterone therapy thicken the blood, and how is it managed?

Large peaks from standard weekly injections appear to overstimulate red blood cell production, thickening the blood — erythrocytosis, the adverse effect TRAVERSE demonstrated most convincingly. Options include smaller, more frequent subcutaneous doses to keep levels steady, lowering the dose, spacing injections, treating contributing sleep apnoea, donating blood, and stopping therapy if the haematocrit stays high. The micro-dosing approach reflects expert clinical experience rather than trial evidence. What is not optional is the monitoring: haematocrit is checked before starting and regularly thereafter, and it is the value that most often dictates a change of plan.

免責事項 This content is written and reviewed by Dr. Soarawee Weerasopone, a board-certified urologist at Bangkok Hospital Headquarters. It is intended for general education only and does not constitute medical advice, diagnosis or treatment for any individual. No advice, diagnosis or prescription is given through personal messaging channels or social media, and Dr. Soarawee operates no public social media account. Always consult a qualified doctor before starting or changing any medical treatment. If you develop chest pain, sudden breathlessness, swelling in one calf or a sudden severe headache with weakness while on testosterone therapy, seek emergency care rather than waiting for an appointment. In an emergency in Thailand, call 1669.