{"id":10984,"date":"2026-09-30T20:00:00","date_gmt":"2026-09-30T13:00:00","guid":{"rendered":"https:\/\/drsoaraweeurology.com\/?p=10984"},"modified":"2026-08-29T16:19:37","modified_gmt":"2026-08-29T09:19:37","slug":"hypogonadism-101-low-testosterone-explained","status":"publish","type":"post","link":"https:\/\/drsoaraweeurology.com\/ja\/2026\/09\/30\/hypogonadism-101-low-testosterone-explained\/","title":{"rendered":"\u4f4e\u30c6\u30b9\u30c8\u30b9\u30c6\u30ed\u30f3\u75c7\u5019\u7fa4101\uff1a\u6ccc\u5c3f\u5668\u79d1\u533b\u306b\u3088\u308b\u4f4e\u30c6\u30b9\u30c8\u30b9\u30c6\u30ed\u30f3\u75c7\u5019\u7fa4\u306b\u3064\u3044\u3066"},"content":{"rendered":"\n
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\"Dr.<\/figure>\n<\/div>\n\n\n\n
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Soarawee Weerasopone, Urologist<\/a><\/strong><\/p>\n\n\n\n

Bangkok hospital Headquarter, Bangkok<\/a><\/p>\n\n\n\n

Samitivej Sriracha hospital, Chonburi \u2014 088-022-1445<\/a><\/p>\n\n\n\n

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Book a Consultation<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

Low testosterone may be one of the most talked-about and least understood topics in men\u2019s health. It is marketed heavily, self-diagnosed frequently, and treated \u2014 often \u2014 by people who never confirmed it in the first place. So during my time at Baylor College of Medicine, I sat down with a colleague I admire greatly to cut through the noise.<\/p>\n\n\n\n

Basil Z. Kaaki, DMSc, PA-C<\/strong> is an Assistant Professor in the Scott Department of Urology at Baylor College of Medicine in Houston, and one of the warmest and most generous teachers I met during my time there. He gives a lecture he calls Hypogonadism 101: The Nuts and Bolts<\/em>, and I asked him to walk through it with me \u2014 in plain language, for men who are trying to make sense of this without a medical degree. What follows is our conversation, lightly edited for clarity.<\/p>\n\n\n\n

One note before we begin. Dr. Kaaki practises in the United States, so what he describes is American practice. Drug availability and regulation differ from country to country, and I have flagged the main difference below where it matters most.<\/em><\/p>\n\n\n\n

Let\u2019s start simply. What is hypogonadism?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> At its core, hypogonadism just means the body is not producing enough testosterone \u2014 the main male hormone. And here is something people find surprising: humans have understood the importance of the testes for centuries, long before anyone knew what a hormone was.<\/p>\n\n\n\n

Think of the castrati \u2014 boys in the sixteenth to nineteenth centuries who were castrated before puberty to preserve their high singing voices. Without testosterone, their voices never deepened, their bones kept growing so they became unusually tall, and their bodies developed very differently. It was a tragic practice, but it was an unmistakable demonstration of what happens when testosterone is absent.<\/p>\n\n\n\n

Then in the 1880s, a prominent physiologist named Brown-S\u00e9quard, in his seventies and feeling his strength fade, injected himself with extracts ground from animal testicles and declared he felt decades younger \u2014 that he could run up stairs again. The science was dubious, his colleagues were unimpressed, and we would now put most of what he felt down to expectation rather than hormone. But he had stumbled onto a real idea: something inside the testes governs male vitality. That something was testosterone, which was not actually isolated and synthesised until the 1930s \u2014 work that earned a Nobel Prize.<\/p>\n\n\n\n

Dr. Pom:<\/strong> So the instinct was right centuries before the chemistry caught up.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> Exactly. And testosterone turned out to matter far more broadly than anyone expected. It is not only about libido and erections. It affects muscle and strength, bone density, mood and motivation, the making of red blood cells, body hair, fat distribution \u2014 it touches almost every system. When it drops too low, men feel it across all of those areas at once, which is part of why the symptoms can be so vague and easy to miss.<\/p>\n\n\n\n

How does the body actually control testosterone?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> The simplest way to picture it is a thermostat \u2014 the kind that keeps your house at a set temperature.<\/p>\n\n\n\n

The brain has two control centres, the hypothalamus and the pituitary gland, that constantly monitor the testosterone level in the blood. When they sense it dropping, they send out signalling hormones that tell the testes to produce more. When the level is high enough, the brain eases off. It is a feedback loop, running quietly in the background all day, keeping things in balance \u2014 and testosterone naturally peaks in the early morning, which becomes important later.<\/p>\n\n\n\n

Dr. Pom:<\/strong> And that loop is the key to understanding why two men with identical low testosterone can have completely different underlying problems.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> That is the whole game, really. Figuring out where<\/em> in that loop the breakdown is happening is the single most important job we have \u2014 because it changes everything about how we treat the man.<\/p>\n\n\n\n

What is the difference between primary and secondary low testosterone?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> This is the distinction every man deserves to have explained to him, because it is so often skipped.<\/p>\n\n\n\n

Primary hypogonadism<\/strong> means the problem is in the testes themselves. The brain is sending the signal correctly \u2014 shouting, even \u2014 but the testes cannot respond. Causes include certain genetic conditions, undescended testicles, chemotherapy or radiation, serious infection, or physical injury. In the lab we see low testosterone but high<\/em> levels of the brain\u2019s signalling hormones, because the brain keeps shouting louder at testes that will not answer.<\/p>\n\n\n\n

Secondary hypogonadism<\/strong> means the testes are fine, but the brain is not sending the signal. Here the cause sits in the hypothalamus or pituitary. This is actually the more common pattern, and many of its causes are things we can influence: obesity, metabolic syndrome, opioid painkillers, long-term steroid use, chronic stress, and simply ageing. In the lab we see low testosterone alongside low or normal signalling hormones \u2014 the brain has gone quiet.<\/p>\n\n\n\n

Dr. Pom:<\/strong> And that difference is not academic \u2014 it points to very different treatments.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> Completely. If a man\u2019s low testosterone is being driven by obesity or opioids or poor sleep, the right answer might be to address those<\/em> things rather than reach straight for a hormone. Occasionally, when testosterone is very low or the signalling hormones behave strangely, we will even image the pituitary gland to make sure there is not a small growth there affecting hormone production. You cannot make that call without doing the workup properly.<\/p>\n\n\n\n

What symptoms should make a man wonder about low testosterone?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> They fall into three broad groups.<\/p>\n\n\n\n

There are physical<\/strong> symptoms: persistent fatigue, loss of muscle and strength, gaining fat especially around the middle, reduced endurance, and less body or facial hair. There are sexual<\/strong> symptoms: reduced libido and erectile difficulty. And there are cognitive and mood<\/strong> symptoms: low mood, irritability, poor concentration, fuzzy memory, and a general loss of drive or motivation.<\/p>\n\n\n\n

Dr. Pom:<\/strong> Which is a tricky list, because every one of those things has other explanations too.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> That is precisely the problem. Fatigue and low mood and weight gain are among the most common complaints in all of medicine, and most of the time they are not<\/em> caused by low testosterone. That is why symptoms alone are never enough. You need the symptoms and<\/em> the blood tests to line up before you have a real diagnosis.<\/p>\n\n\n\n

How is it diagnosed properly?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> Three rules, and each exists for a reason.<\/p>\n\n\n\n

First, the blood must be drawn in the early morning<\/strong>. Remember testosterone peaks early in the day \u2014 so a level taken in the afternoon can look falsely low and lead to treating a man who is actually fine.<\/p>\n\n\n\n

Second, you need two separate measurements<\/strong> on different days. Testosterone naturally fluctuates, and a single low reading can be a blip \u2014 illness, poor sleep, or stress can all temporarily suppress it. Guidelines are clear that one number is not enough.<\/p>\n\n\n\n

Third \u2014 and this is the one people forget \u2014 a low number on its own is not<\/strong> a diagnosis. The threshold urologists commonly use is a total testosterone below 300 ng\/dL, but the diagnosis of testosterone deficiency is only made when a low level is combined with<\/em> genuine symptoms. A man with a low number and no symptoms generally does not need treatment.<\/p>\n\n\n\n

Dr. Pom:<\/strong> This is where a lot of the low-testosterone industry falls down \u2014 treating a number instead of a patient.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> It is my single biggest frustration in this field. A proper evaluation also looks beyond testosterone \u2014 we check blood count, blood sugar, cholesterol, thyroid, vitamin levels, prostate markers in older men, and more. Sometimes the low testosterone is a clue pointing to something else entirely that deserves attention. Rushing to a prescription skips all of that.<\/p>\n\n\n\n

Let\u2019s talk treatment. What are the options?<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> More than most men realise, and the best choice depends heavily on the individual \u2014 especially on one question I always ask early: do you want to have children in the future?<\/em><\/p>\n\n\n\n

The forms of testosterone replacement used here in the United States are gels<\/strong> applied to the skin daily, injections<\/strong> given weekly or less often, pellets<\/strong> placed under the skin every few months, a nasal<\/strong> gel, and newer oral capsules<\/strong>. Each has trade-offs. Gels are easy but can transfer to a partner by skin contact. Injections are effective and inexpensive but levels can peak and dip. Pellets are convenient \u2014 set and forget for months \u2014 but require a small in-office procedure.<\/p>\n\n\n\n

Dr. Pom:<\/strong> This is the difference worth flagging for readers here. That list is the American menu. In Thailand the picture is narrower: the testosterone therapy I provide at Bangkok Hospital Headquarters is given as gel or injection<\/strong>. Pellets, nasal gel and oral capsules are not part of what is available here, so if you have read about them on an overseas website, that is why. It changes very little clinically \u2014 gels and injections are the two workhorses everywhere \u2014 but you should not arrive expecting a pellet.<\/p>\n\n\n\n

And there is a crucial catch with standard testosterone replacement that many men are never told about.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> This is so important. When you give a man external testosterone, his brain senses plenty of hormone in the blood and switches off its own signal to the testes. The problem is that the testes need that signal to keep making sperm. So conventional testosterone therapy can dramatically reduce a man\u2019s fertility<\/strong> \u2014 sometimes to zero \u2014 while he is on it. For a young man hoping to father children, prescribing standard testosterone without discussing this is a serious mistake. And recovery after stopping is usually good but not guaranteed, and can take many months.<\/p>\n\n\n\n

Dr. Pom:<\/strong> So what do you offer the man who wants both \u2014 better symptoms and preserved fertility?<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> This is where it gets interesting, because we have medications that raise a man\u2019s own<\/em> testosterone rather than replacing it from outside.<\/p>\n\n\n\n

One group nudges the brain to send a stronger<\/em> signal to the testes, so the man makes more of his own testosterone while continuing to produce sperm. Another option mimics the brain\u2019s signalling hormone directly, keeping the testes switched on. These fertility-sparing approaches are used off-label for this purpose \u2014 meaning they are prescribed for a use outside their original licence, which is common and legitimate in medicine but is something you should be told rather than discover later. For the right patient, typically a younger man with the secondary type of low testosterone who wants children, they can be an excellent choice. And for some men, simply losing weight, sleeping better, and coming off medications that suppress testosterone raises their level without any hormone at all.<\/p>\n\n\n\n

What about safety? Men hear frightening things about testosterone.<\/h2>\n\n\n\n

Dr. Kaaki:<\/strong> They do, and much of it is out of date. Let me take the big worries in turn.<\/p>\n\n\n\n

Prostate cancer.<\/strong> For decades men were told testosterone would cause or feed prostate cancer. The evidence has not supported that fear, and guidelines now state there is no proven link between testosterone therapy and the development of prostate cancer. We still sensibly check prostate health before starting treatment in older men, but the old blanket fear was misplaced.<\/p>\n\n\n\n

Thickened blood.<\/strong> This one is real and worth monitoring. Testosterone can raise the red blood cell count, making the blood thicker, which is why we check a blood count before starting and periodically afterwards. It is manageable \u2014 but it is a genuine reason you need supervision rather than a hormone bought online.<\/p>\n\n\n\n

The heart.<\/strong> This is the biggest shift of all. For years testosterone products in the United States carried a strong cardiovascular warning. But after a very large, rigorous trial found no increase in heart attacks or strokes in men treated appropriately, the regulators removed that warning in 2025<\/strong>. That is a significant change, and it has reassured a lot of doctors and patients.<\/p>\n\n\n\n

Dr. Pom:<\/strong> I wrote about that trial in detail recently, because the distinction between testosterone being safe<\/em> for the heart versus protective<\/em> for the heart is one people constantly blur \u2014 readers can find that discussion of the landmark heart-safety trial here<\/a>.<\/p>\n\n\n\n

One detail in that trial is reported loosely almost everywhere, so let me be precise about it. The treated group did record more atrial fibrillation, more blood clots in the lungs and more acute kidney injury than the placebo group \u2014 but those differences were numerically higher without reaching statistical significance<\/strong>. They are signals worth watching, not established harms, and describing them as proven risks overstates what the trial showed. Two findings did reach significance: a rise in the red blood cell count, which is what Dr. Kaaki has just described, and roughly 43% more clinical fractures<\/strong> in the treated group. So the honest summary is that the clearest measurable effects of treatment are on the blood count and on bone, and those are exactly what monitoring is designed to catch.<\/p>\n\n\n\n

Dr. Kaaki:<\/strong> That distinction is exactly right, and it matters. Testosterone, prescribed properly to a man who genuinely needs it and monitored the way it should be, is a safe and effective treatment. The danger is not testosterone itself \u2014 it is testosterone taken without a diagnosis, without monitoring, and without a conversation about fertility.<\/p>\n\n\n\n

Final thoughts<\/h2>\n\n\n\n

Dr. Pom:<\/strong> My thanks to Dr. Kaaki for his time and his generosity \u2014 both in this conversation and throughout my time as a Research Scholar and Clinical Observer at Baylor.<\/p>\n\n\n\n

If there is one message to carry away, it is that low testosterone is a real medical condition that deserves a real medical evaluation \u2014 not a self-diagnosis and not a hormone ordered off the internet. Get the diagnosis confirmed properly, understand whether the problem is in the testes or the brain, protect your fertility if children are in your future, and be monitored by someone who knows what they are doing. Done that way, treatment can make a real difference to how a man feels.<\/p>\n\n\n\n

See how testosterone replacement therapy<\/a> is structured in practice, including the fertility-sparing options and the monitoring that should accompany treatment, and how it connects with erectile dysfunction treatment<\/a>.<\/p>\n\n\n\n

If you have symptoms of low testosterone \u2014 reduced libido, erectile difficulty, persistent fatigue, low mood, or loss of muscle \u2014 please have it assessed properly rather than self-treating. Dr. Soarawee Weerasopone offers specialist consultations in men\u2019s health and testosterone therapy at Bangkok Hospital Headquarters. Book a Consultation<\/a>. Consultations are also available at Samitivej Sriracha Hospital, Chonburi \u2014 please call the department line on 088-022-1445<\/a>.<\/p>\n\n\n\n

Bangkok Hospital Telemedicine is available for patients who cannot attend in person, including international patients \u2014 arrange it in advance by email to the Urology department at bhquro@bdms.co.th<\/a>. A video consultation is a good way to go through symptoms and any results you already have; the confirmatory blood tests are done in person, early in the morning, and on two separate days. Samitivej Sriracha is in-person only. For questions about the cost of consultation or treatment, please contact the Urology department at bhquro@bdms.co.th<\/a> rather than asking here.<\/p>\n\n\n\n

Frequently Asked Questions About Low Testosterone<\/h2>\n\n\n\n

What testosterone level is considered low?<\/h3>\n\n\n\n

Urologists commonly use a total testosterone below 300 ng\/dL as a cut-off supporting a diagnosis of low testosterone. However, the number alone is not a diagnosis. Testosterone deficiency is only diagnosed when a low level, confirmed on two separate early-morning blood tests, occurs together with genuine symptoms such as reduced libido, fatigue, or loss of muscle. A man with a low reading but no symptoms usually does not require treatment. Note also that reference ranges vary between laboratories, so a result should be read against the range printed on your own report.<\/p>\n\n\n\n

Why does testosterone need to be tested in the morning?<\/h3>\n\n\n\n

Testosterone follows a daily rhythm and peaks in the early morning, then declines through the day. A level drawn in the afternoon can appear falsely low and lead to unnecessary treatment. For this reason, guidelines recommend measuring testosterone in the early morning, and confirming a low result with a second early-morning test on a different day before making any diagnosis.<\/p>\n\n\n\n

Does testosterone therapy cause infertility?<\/h3>\n\n\n\n

Conventional testosterone replacement can significantly reduce fertility, sometimes to zero, while a man is taking it. This happens because external testosterone causes the brain to switch off the signal the testes need to produce sperm. Recovery after stopping is usually good but is not guaranteed and can take many months. Men who wish to preserve fertility should not be started on standard testosterone without discussing this. Fertility-sparing alternatives exist that raise a man\u2019s own testosterone while maintaining sperm production, and are often preferred for younger men who want children.<\/p>\n\n\n\n

What is the difference between primary and secondary hypogonadism?<\/h3>\n\n\n\n

Primary hypogonadism means the testes themselves cannot produce enough testosterone despite the brain signalling correctly, with causes including genetic conditions, chemotherapy, radiation, infection, or injury. Secondary hypogonadism means the testes are capable but the brain is not sending the signal, with common causes including obesity, metabolic syndrome, opioid medications, chronic stress, and ageing. Distinguishing the two through blood tests is essential because they call for different treatments.<\/p>\n\n\n\n

Is testosterone therapy safe for the prostate and heart?<\/h3>\n\n\n\n

Current evidence is reassuring on both, but the detail matters. Guidelines state there is no proven link between testosterone therapy and the development of prostate cancer, though prostate health is still checked before treatment in older men. For the heart, a large rigorous trial found no increase in heart attacks or strokes in appropriately treated men, and United States regulators removed the previous cardiovascular warning from testosterone products in 2025. In that same trial, atrial fibrillation, pulmonary embolism and acute kidney injury were numerically more common in the treated group but did not reach statistical significance, so they are signals to watch rather than established harms. Two findings did reach significance: a rise in the red blood cell count, and roughly 43% more clinical fractures. Monitoring during treatment is therefore not optional.<\/p>\n\n\n\n

Which forms of testosterone are available in Thailand?<\/h3>\n\n\n\n

The testosterone therapy provided at Bangkok Hospital Headquarters is given as a transdermal gel or as an injection. Pellets placed under the skin, nasal gel, and newer oral capsules are used in some other countries, particularly the United States, but are not part of what is offered here. This makes little clinical difference, since gels and injections are the two most widely used forms worldwide, but it is worth knowing if you have been reading overseas material.<\/p>\n\n\n\n

Can I discuss low testosterone by video consultation?<\/h3>\n\n\n\n

Yes. Bangkok Hospital Headquarters offers a Telemedicine service, arranged in advance by emailing the Urology department at bhquro@bdms.co.th. A video consultation is well suited to reviewing symptoms, previous test results and current medications, and to planning what testing is worthwhile. The blood tests that confirm the diagnosis are done in person, early in the morning, and on two separate days. Samitivej Sriracha Hospital is in-person only.<\/p>\n\n\n\n

Featuring:<\/strong> Dr. Basil Kaaki, DMSc, PA-C \u2014 Assistant Professor, Scott Department of Urology, Baylor College of Medicine, Houston, Texas. Quoted with his permission.<\/p>\n\n\n\n

Written & hosted by:<\/strong> Dr. Soarawee Weerasopone (Dr. Pom) \u2014 Board-Certified Urologist, Bangkok Hospital Headquarters.
Fellowship in Andrology, Chang Gung Memorial Hospital Kaohsiung, Taiwan (2019) \u00b7 Fellowship in Robotic Surgery & Minimally Invasive Urology, Chang Gung Memorial Hospital, Taiwan (2019) \u00b7 Endourology Observership, Juntendo University, Japan (2022) \u00b7 Research Scholar & Clinical Observer, Scott Department of Urology, Baylor College of Medicine, USA (2025\u20132026)<\/p>\n\n\n\n