The Symptoms Attributed to Low Testosterone, and How Non-Specific They Are

Search for low testosterone and you will find a checklist within seconds. Fatigue. Low libido. Weight gain around the middle. Low mood. Loss of strength. Poor sleep.

Every item on that list is genuinely associated with low testosterone. Every item is also associated with depression, hypothyroidism, iron deficiency, sleep apnoea, chronic stress, poor diet and simply being in one's forties. That is the problem with symptom checklists in this field: they are sensitive and almost entirely non-specific.

Why the sexual symptoms discriminate and the others do not

The three sexual symptoms showed a syndromic relationship with testosterone: they clustered together and their probability increased as levels fell, particularly below roughly 8 nmol/L for total testosterone. The physical and psychological symptoms did not show this relationship in the same way.

This does not mean fatigue is unrelated to testosterone. It means fatigue is caused by so many things that its presence tells you very little on its own.

The symptoms worth taking seriously

Reduced morning erections

Nocturnal and morning erections are a rough daily readout of both hormonal and vascular function. A sustained decline in frequency is among the earliest and more specific signals, and it is also the one men are least likely to raise with a clinician.

Reduced sexual thoughts

A drop in spontaneous sexual interest, distinct from performance and not attributable to a relationship or life circumstance, is one of the more discriminating markers.

Erectile dysfunction

Associated with low testosterone, but also strongly associated with cardiovascular disease. New-onset ED is a reason to see a doctor for reasons well beyond hormones, since it can be an early marker of endothelial dysfunction.

The symptoms that need a differential

• Fatigue. Consider anaemia, thyroid dysfunction, sleep apnoea, depression, and simple sleep debt first.
• Weight gain. Bidirectional with testosterone: excess adiposity lowers it, and low levels promote fat storage. Which came first is rarely obvious.
• Low mood. Overlaps heavily with depression, which is both more common and more treatable.
• Loss of strength. Confounded by training status, protein intake and age.

What to do with a symptom list

Treat it as a prompt to measure, not as a diagnosis. A morning blood test for total and free testosterone, repeated on a second occasion, is the only thing that converts a suspicion into a fact. We set out what that involves in our guide to testing.

This matters commercially as well as clinically. A symptom checklist that concludes "you probably have low testosterone, here is what to buy" is selling to a population in which most people do not have the condition. The honest version concludes with a blood test.