Men often come to us asking about testosterone because they feel low on energy, sex drive and focus. Some of them also snore, wake up tired or fight sleep at their desk. When I hear that mix, I ask about sleep before I talk about hormones.
The reason is that sleep apnea and low testosterone often travel together, and each one can make the other worse. Body fat plays a part in both problems. If we treat only the hormone, we can miss the airway, and testosterone therapy can even make an untreated airway problem worse.
What Obstructive Sleep Apnea Is
Obstructive sleep apnea (OSA) means your upper airway closes, fully or in part, again and again while you sleep. Each event lowers the oxygen in your blood and breaks up your sleep. An apnea is a pause in breathing that lasts 10 to 40 seconds, even while you try to breathe.
Doctors grade OSA with the apnea-hypopnea index (AHI), which counts pauses and shallow breaths per hour of sleep. An AHI under 5 is normal, mild OSA is 5 to 15 events an hour, moderate is 15 to 30, and severe is over 30.
OSA is common, and it is more common in men and in people with obesity. Estimates range from 9% to 38% of the general population, and reach 50% to 60% in people with obesity.
Testosterone Is Made While You Sleep
Most of a man's daily testosterone release happens during sleep. In young men, levels start to rise soon after sleep begins and stay high until waking. Levels then fall the longer you stay awake, so testosterone runs highest in the morning and lowest late in the day. The rise needs at least 3 hours of sleep with normal sleep stages, and broken sleep all night can block it.
A 2011 study in JAMA tested this in 10 healthy young men who were limited to 5 hours in bed a night for one week. After that week, their daytime testosterone was 10% to 15% lower than after well-rested nights. For comparison, the authors note that normal aging lowers testosterone by 1% to 2% a year.
The men also felt the change, as their vigor scores fell from 28 after the first short night to 19 after the seventh. The study was small and used young men, so treat the exact numbers with caution. The direction is clear, though: less sleep, less testosterone.
How Sleep Apnea Lowers Testosterone
Sleep apnea can lower testosterone production in two ways. First, it breaks up sleep: men with OSA get less deep sleep and less REM sleep, and they wake more often. Second, it drops blood oxygen over and over through the night.
In some studies, men with a higher AHI had lower testosterone, and deeper drops in oxygen also tracked with lower testosterone. Researchers still debate how much of this comes from the apnea itself, because the same men often carry extra weight.
Body fat is the third factor, and it may be the largest. Fat tissue contains an enzyme called aromatase, which turns testosterone into estradiol, a form of estrogen. Obesity also lowers SHBG (sex hormone-binding globulin), the protein that carries testosterone in the blood.
One large study shows why weight matters so much. In 1,312 men aged 65 and older, a higher AHI went with lower testosterone in the raw data. After the researchers adjusted for body weight or waist size, that link disappeared or became much weaker.
A 2014 review concluded that weight, more than the apnea itself, explains low testosterone in men with OSA. Sleep apnea may still act indirectly, by making weight gain more likely.
How Low Testosterone Feeds the Cycle
The links also run the other way. Low testosterone goes with more abdominal fat, including visceral fat, which sits deep in the belly around your organs. Low testosterone may also promote further weight gain, and testosterone helps you keep muscle mass and strength.
More weight then makes sleep apnea worse. A Wisconsin study tested the sleep of 690 adults twice, 4 years apart, and tracked their weight. A 10% weight gain predicted about a 32% rise in AHI and a 6-fold rise in the odds of moderate to severe sleep apnea.
Testosterone therapy adds a separate risk, because it can worsen sleep apnea in some men. The Endocrine Society advises against starting testosterone in men with untreated severe sleep apnea. In one trial in men with obesity and sleep apnea, testosterone mildly worsened oxygen drops during sleep at 7 weeks, but not at 18 weeks.
Red blood cells are a second concern. Sleep apnea may raise the red blood cell count, and testosterone can raise it further in some men. The Endocrine Society calls for checking hematocrit, the share of your blood made of red cells, during treatment.
Will CPAP Raise Testosterone?
CPAP (continuous positive airway pressure) uses a mask and steady air pressure to keep your airway open. It is the first-choice treatment for moderate to severe sleep apnea. Many men hope it will also raise their testosterone, but the evidence says it usually does not.
A 2019 meta-analysis pooled 12 studies with 388 men and found that CPAP did not significantly change total testosterone. The result held for men who started with low testosterone, though that group showed a trend upward. One likely reason is that CPAP treats the airway but does not reduce body weight, which drives both problems.
Treat the sleep apnea anyway, because untreated sleep apnea is linked to high blood pressure, heart attack, stroke and diabetes. Treatment may also help sexual function, especially in men with severe sleep apnea.
Weight loss helps both problems at once. In the Wisconsin study, a 10% weight loss predicted a 26% drop in AHI. On the hormone side, testosterone in men with obesity rises in proportion to the weight they lose. Results vary from man to man.
NICE, the national guideline body in England, advises support with weight loss for everyone with OSA. It also advises help to stop smoking, cut alcohol and improve sleep habits.
What we don't know: Most studies on this topic are small, short or observational. In the CPAP meta-analysis, only three studies reported that men used CPAP enough (at least 4 hours a night on 70% of nights). So the results may partly reflect CPAP that men did not use enough. The long-term effect of testosterone therapy on sleep apnea also remains unclear.
From our practice: A man came to us with fatigue, daytime sleepiness and lab results that showed poor metabolic health. On further questioning, he met criteria for sleep apnea. His testosterone was also low, but we did not start with testosterone.
His plan had three parts: nutrition, exercise and tirzepatide. The FDA has approved tirzepatide to treat moderate to severe obstructive sleep apnea in adults with obesity. His sleep quality and metabolic numbers improved, and his testosterone rose without testosterone therapy. This is one patient, and results vary.
How We Approach It
We screen sleep before we treat hormones. NICE advises a sleep assessment when a person has two or more of these features:
- Snoring
- Breathing pauses that a partner notices
- Sleep that leaves you unrefreshed
- Headaches when you wake up
- Sleepiness, tiredness or fatigue you cannot explain
- Waking at night to urinate
- Choking during sleep
- Broken sleep or insomnia
- Trouble with memory or thinking
NICE also notes that sleep apnea is more common with obesity, type 2 diabetes, and high blood pressure that stays high despite treatment. If those signs are present, we recommend a sleep evaluation before we discuss testosterone therapy.
We also measure testosterone the way the Endocrine Society recommends. That means a fasting blood draw in the morning, when levels run highest, and a repeat test to confirm a low result. One low reading is not a diagnosis.
Our biomarker panel includes total and free testosterone, SHBG, LH and FSH, and a complete blood count. To make sense of your own results, start with our guide to reading your lab panel. Depending on what we find, your plan may draw on our Recovery & Resilience or Metabolic & Hormonal work. When weight is part of the picture, our weight management program is often part of the plan.
The order matters: I want to know how a man breathes at night before I discuss testosterone therapy. Starting testosterone on top of untreated severe sleep apnea goes against guideline advice. A sleep evaluation first keeps him out of that situation.
Start With How You Breathe at Night
A man who snores and feels drained often expects a hormone answer. Sometimes the better first question is how he breathes at night. Get that question answered before you start testosterone, while the answer can still shape the plan.