Long-term low testosterone has six consequences that come up again and again: bone, muscle, mood, libido, metabolism and fertility. First things first: these are associations from research, not proven cause and effect. A low number doesn't automatically mean these things happen to you.
What strikes me in practice is that men get spooked by lists like this. That's not my aim. I want to show you where the link is real, and where it stops.
Picture a man of 50 who spent years with a testosterone around 8 nmol/l, untreated. A bone-density scan (DEXA) shows a lower bone density in him. His story comes back later.
Is long-term low testosterone dangerous?
A low number on its own is not a disease. Long-term low testosterone is, however, associated in research with several consequences, such as lower bone density and less muscle mass. Association is not the same as cause: age, weight and other conditions often play in at once. So discuss a low result with your GP.
The RIVM, the Dutch public-health institute, tracks men's health and stresses that lifestyle and existing conditions weigh heavily. That is exactly why one hormone value is rarely the whole picture.
| Consequence | Possible mechanism | Which value adds context |
|---|---|---|
| Lower bone density | Less hormonal signal for bone maintenance | Total testosterone |
| Less muscle mass and strength | Reduced muscle protein build-up | Total testosterone |
| Low or irritable mood | Influence on mood regulation in the brain | Total testosterone |
| Lower libido and erection problems | Testosterone helps drive sexual desire | Total testosterone, free testosterone |
| More belly fat and insulin resistance | Unfavourable fat distribution and metabolism | Total testosterone, SHBG |
| Reduced fertility | Disturbed LH/FSH signalling to the testes | LH, FSH |
1. Bone loss and lower bone density
Testosterone plays a part in maintaining your bones. Some of it is converted into estradiol, which matters for bone density in men. With long-term low testosterone that signal is sometimes weaker.
In a study of older men, a deficiency of testosterone and estradiol went together with more bone loss and osteoporosis (Fink, 2006). It is a link, not proof that one causes the other.
Back to that man of 50 at 8 nmol/l. His DEXA shows a lower bone density, but he also smoked and moved little. That is exactly why a doctor never looks at the hormone alone.
2. Loss of muscle mass and strength
Testosterone helps build muscle protein. If the hormone stays low for a while, muscle mass can slowly decline. Many men notice it as less strength or a softer shape.
That the hormone drives muscle is clear in dose research: the higher the testosterone dose given, the more fat-free mass increased (Bhasin, 2001). That shows the mechanism, not that your muscles are guaranteed to disappear.
In practice I see strength fade slowly. So men put it down to getting older, while sometimes there is more going on.
3. Low or irritable mood
Mood and hormones are linked, in both directions. Low testosterone is sometimes associated with low mood, listlessness and irritability. The other way round, depression can also affect your hormones.
A review found a small link between low testosterone and depressive symptoms (Zarrouf, 2009). Small and not clear-cut: far from everyone with low mood has low testosterone.
So this is the hardest signal to read from the value alone. Low mood has many possible causes, and your GP weighs them together.
4. Lower libido and more erection problems
Of all the complaints, libido tracks testosterone most clearly. Less interest in sex is more common with a low hormone than erection problems, which often have more to do with the blood vessels.
The EMAS study of over 3,000 men saw sexual complaints clearly relate to testosterone only below roughly 11 nmol/l (Wu, 2010). Above that line the link weakened quickly.
What strikes me: men reach for testosterone first when they have erection problems. Yet the number is often normal there. We work that out in the signs of low testosterone.
5. More belly fat and a less favourable metabolism
Testosterone and your metabolism affect each other both ways. Low testosterone goes together more often with belly fat and a less favourable insulin sensitivity. Belly fat, in turn, converts testosterone into estrogen, which can push the value down further.
In a large study of middle-aged men, low testosterone and low SHBG more often predicted the metabolic syndrome and diabetes (Laaksonen, 2004). Here too: a predictor is not a cause.
This is the vicious circle I explain to men most often. Weight and hormone drag each other the wrong way.
6. Reduced fertility and sperm quality
Your testes make both testosterone and sperm cells, driven by two hormones from the pituitary: LH and FSH. If that signalling is off, both testosterone and sperm production can suffer.
Here the source of the low testosterone matters. If the problem sits in the testes themselves (primary), LH and FSH are actually high. If it sits in the pituitary (secondary), they are low. So those two values point the way.
Note: taking testosterone as a medicine can actually suppress your own production and sperm output. So always discuss a wish to have children with your GP before you do anything.
What can you have measured?
No blood test predicts these consequences. A few values do map your hormonal picture. A doctor usually looks at your total testosterone, and uses LH and FSH to tell primary from secondary.
The NHG, the Dutch College of General Practitioners, describes in its guidance for GPs which physical factors play into this. What you need, your GP decides together with you.
My advice stays simple: don't chase a single number, look at the context. If persistent fatigue or low mood makes you doubt, read burnout or low testosterone, because the two look a lot alike.
Want to see your hormones? The Men's Hormones panel measures testosterone, LH and FSH in one go, among others. For the bigger picture, read men's hormonal health.
To find out where a low value comes from, see the causes of low testosterone and the deficiencies that can lower your testosterone.
References
- Fink HA, Ewing SK, Ensrud KE, et al. Association of testosterone and estradiol deficiency with osteoporosis and rapid bone loss in older men. J Clin Endocrinol Metab. 2006;91(10):3908-3915. PMID 16849417.
- Bhasin S, Woodhouse L, Casaburi R, et al. Testosterone dose-response relationships in healthy young men. Am J Physiol Endocrinol Metab. 2001;281(6):E1172-E1181. PMID 11701431.
- Zarrouf FA, Artz S, Griffith J, Sirbu C, Kommor M. Testosterone and depression: systematic review and meta-analysis. J Psychiatr Pract. 2009;15(4):289-305. PMID 19625884.
- Wu FC, Tajar A, Beynon JM, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med. 2010;363(2):123-135. PMID 20554979.
- Laaksonen DE, Niskanen L, Punnonen K, et al. Testosterone and sex hormone-binding globulin predict the metabolic syndrome and diabetes in middle-aged men. Diabetes Care. 2004;27(5):1036-1041. PMID 15111517.
- RIVM (National Institute for Public Health and the Environment) and NHG (Dutch College of General Practitioners): general information on men's health and lifestyle factors.
Disclaimer
Caliberhealth works with BIG-registered doctors who review your blood results. This article offers general information and does not replace medical advice from your GP or specialist. A blood test is a tool, not a diagnosis on its own. For persistent or serious symptoms, contact your GP, or call 112 in an emergency.
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