Testosterone decline in young men

Data on young men

Low testosterone is often talked about as something that belongs to middle-aged and older men. The data suggest the picture is more nuanced. Lokeshwar and colleagues (European Urology Focus, 2021) went through the American NHANES survey for men aged 15–39 and found that mean total testosterone fell from one survey round to the next. The decline persisted after adjusting for factors such as age and weight, and it was also present in men with a normal BMI. So it is not only an obesity story, even though obesity clearly lowers testosterone.

The finding does not stand alone. Perheentupa and colleagues (European Journal of Endocrinology, 2013) had already shown the same generational pattern in Finnish population surveys, where younger birth cohorts had lower values than older cohorts at the same age. Andersson and colleagues (JCEM, 2007) found a similar pattern in Danish population surveys. Travison and colleagues (JCEM, 2007) showed in the American MMAS study that the decline between generations cannot be explained only by men getting older.

What does this mean in practice?

It does not mean that all young men have low testosterone. The vast majority are fine. But it does mean that "you are too young" is not an argument in itself. Age is a poor filter for a condition that is defined by a measurement. A 28-year-old with fatigue, low drive, poor recovery after training, reduced libido and testosterone at the bottom of the healthy young range is not protected by his age.

There is also a problem with reference ranges. Many laboratories use the same range for a man of 25 and a man of 65. A number that is entirely ordinary for a 65-year-old can be low for a 25-year-old. When the result simply reads "normal", that difference disappears. We have written more about it in why your blood results are normal.

In young men there is more often a cause

At the same time, low testosterone in a young man more often has a cause that can be found and treated. That is the most important message of this article. Typical causes are:

• Excess weight, especially fat around the abdomen
• Sleep apnoea and generally too little or poor sleep
• Opioids and certain other medicines
• Previous use of anabolic steroids, which can suppress the body's own production for a long time
• Prolactinoma, a benign tumour of the pituitary gland
• Thyroid and metabolic disorders
• Coeliac disease and other conditions that affect nutrient absorption
• A primary problem in the testicles

Many of these can be uncovered with quite ordinary blood tests. That is a reason to investigate properly, not to start treatment quickly.

Lifestyle is not an insult

When the cause is weight, sleep or alcohol, being asked to look at them is not a dismissal. Weight loss in overweight men often raises testosterone, and treating sleep apnoea can do the same. It is not lifestyle or investigation. It is both, and the measurements show whether the changes work. If the numbers stay low even when the obvious causes have been dealt with, that is an important finding in itself.

Free testosterone and SHBG

Total testosterone is not the whole picture. A large part of the hormone is bound to the protein SHBG and is not freely available to the body's tissues. Two men with the same total testosterone can therefore have very different free testosterone. In young, lean and very active men SHBG can be high, so free testosterone is lower than the total suggests. Read more in SHBG, the hormone that decides your free testosterone.

Fertility must be part of the decision

For a young man there is an extra reason to be thorough. Added testosterone suppresses the body's own signals to the testicles and can therefore reduce sperm production markedly. If you want children now or later, this must be discussed with the doctor before treatment is even considered. It is also one of the reasons why treatment in young men requires a particularly careful work-up.

A sensible order

1. Write down your symptoms and how long you have had them.
2. Take a morning sample, ideally fasting, with total testosterone, SHBG, calculated free testosterone, LH and FSH. LH and FSH show whether the problem lies in the testicles or in the signal from the brain.
3. Repeat a low or borderline number. One measurement is not enough.
4. Have the possible causes above checked, such as prolactin, thyroid and sleep.
5. Only then is treatment discussed, and only if a doctor finds an indication.

The first test can be taken locally, where you live. The result is not a diagnosis in itself, but a starting point for a conversation with a doctor who looks at the numbers together with your symptoms, your medication and your history.

Summary

Data from several countries suggest that testosterone levels are lower today than a generation ago, also in young men and also in men of normal weight. That makes symptoms in young men worth taking seriously. But in young men there is more often a concrete cause, and fertility matters. That is why a thorough work-up is the first step, and any decision about treatment belongs to the doctor.