Low Testosterone: Real Symptoms, Causes, Testing and Treatment

What testosterone does

Testosterone is the principal male sex hormone, made mainly in the testes under the direction of the pituitary gland (via LH and FSH). It drives puberty, then maintains through adult life: sexual desire and erectile function, sperm production, muscle mass and strength, bone density, red blood cell production, body hair, and aspects of mood and cognition.

Production follows a daily rhythm, peaking in the early morning — the reason testing is done before about 10 a.m. — and responds to the body's state: it falls with sleep loss, illness, obesity, heavy drinking and stress, and recovers when they resolve. That responsiveness is exactly why a single low reading proves little.

What actually happens with age

Total testosterone declines gradually — on the order of 1% a year from the mid-thirties — while the protein that binds it (SHBG) rises, so free testosterone falls a little faster. Even so, most men in their seventies remain within the normal range. The dramatic mid-life crash of advertising is not the biology; where levels are genuinely low in mid-life, there is usually a cause beyond the calendar — most often excess weight.

Symptoms

Symptoms sort into two tiers.

Specific — these genuinely point toward low testosterone: - reduced sexual desire and fewer spontaneous erections, including morning erections - erectile difficulty, usually alongside low desire - loss of body and facial hair; shrinking testes - breast tissue enlargement (gynecomastia) - infertility - hot flushes (when levels are very low) - loss of muscle bulk and strength; loss of height or low-trauma fractures from bone thinning

Non-specific — real, but with many likelier causes: - fatigue, low motivation, irritability, low mood, poor concentration, reduced exercise capacity, increased body fat

The full pattern is described in signs of low testosterone. A man with only tier-two symptoms and a normal test does not have a testosterone problem, whatever an advertisement says.

Causes

Primary hypogonadism — the testes cannot produce enough: Klinefelter syndrome, undescended testes, mumps orchitis, injury, chemotherapy or radiation, some autoimmune disease.

Secondary hypogonadism — the pituitary or hypothalamus under-signals: pituitary tumours (including prolactinoma), head injury, iron overload, and — far more commonly — functional suppression by: - obesity, the leading reversible cause (fat tissue converts testosterone to estrogen and suppresses the signalling axis) - obstructive sleep apnea and chronic sleep loss - opioid painkillers and long-term corticosteroids; anabolic steroid use (shuts down natural production, sometimes lastingly) - heavy alcohol use - serious illness, uncontrolled diabetes, kidney or liver disease

Age contributes modestly; the "andropause" of mid-life is usually several of the above wearing a hormonal disguise.

How it is diagnosed

1. Morning total testosterone (before ~10 a.m., fasting preferred), repeated on a second morning if low — levels below roughly 300 ng/dL (10.4 nmol/L) on both occasions support the diagnosis. See the testosterone test guide for the details and pitfalls.
2. Free testosterone (calculated with SHBG) when total is borderline or SHBG is likely abnormal — obesity lowers SHBG, age raises it.
3. LH and FSH to locate the problem: high values point to the testes (primary), low or normal to the pituitary (secondary).
4. Further tests as indicated: prolactin, iron studies, pituitary MRI for significantly low secondary cases; plus glucose, lipids and blood count, because low testosterone travels with metabolic disease.

Treatment

Fix the suppressors first

For functional low testosterone, treating the cause is the treatment: substantial weight loss raises levels meaningfully, as do treating sleep apnea, reducing alcohol, stopping opioids where possible, and resistance exercise. These improve the symptoms directly as well as the number — and they preserve fertility, which testosterone therapy does not.

Testosterone replacement therapy

For confirmed hypogonadism with symptoms, replacement — gels, injections, patches, or long-acting depots — restores levels and, in trials, improves sexual desire, erectile function, mood, bone density, muscle mass and anemia.

What it requires and risks: - Fertility suppression — external testosterone switches off sperm production; men wanting children need different treatment (clomiphene or gonadotropins) under a specialist. - Monitoring — hematocrit (blood can thicken), PSA and prostate assessment per guidelines, liver and lipid checks. - Acne, fluid retention, breast tenderness, possible worsening of sleep apnea. - Cardiovascular safety of properly monitored therapy in deficient men looks reassuring in recent large trials, but therapy for normal levels has no proven benefit and carries the same costs.

Buying testosterone or "boosters" outside medical care — online pharmacies, gyms — risks counterfeits, wrong doses and none of the monitoring.

When to see a doctor

Arrange testing for the specific symptoms above, for infertility, for low-trauma fractures, or before assuming any supplement or clinic advertisement applies to you. Seek prompt advice if low testosterone symptoms come with headaches or visual changes (pituitary), or if you have used anabolic steroids and symptoms persist after stopping.

Can supplements play a supportive role?

"Testosterone booster" is a marketing category, not a pharmacological one. The honest evidence — a modest signal for ashwagandha and tongkat ali in specific situations, little or nothing for most famous names — is reviewed in Do testosterone boosters work?. Nothing sold over the counter substitutes for diagnosis, for fixing the reversible causes, or for replacement where it is genuinely needed.

Frequently asked questions

References