Testosterone, beyond the marketing

Testosterone prescribing has risen dramatically in several countries over the past two decades, considerably faster than any plausible increase in the underlying condition.

What it does

In men, testosterone drives development at puberty and maintains muscle mass, bone density, red cell production, body hair, libido and aspects of mood and energy.

Women produce it too, in smaller amounts, and it contributes to libido, energy and bone health.

Levels decline gradually with age in men — on average around one per cent a year from midlife — which is a slow drift rather than an abrupt event, and which is where much of the marketing language about a male menopause comes from.

Genuine deficiency

Hypogonadism means consistently low testosterone alongside symptoms, and it has two distinct forms.

Primary, where the testes themselves are not producing — from injury, infection, chemotherapy, certain genetic conditions.

Secondary, where the signal from the pituitary is inadequate — from pituitary disease, opioids, steroids, severe illness, and notably obesity, which suppresses the axis through several mechanisms.

Symptoms include reduced libido, erectile difficulty, loss of morning erections, fatigue, reduced muscle mass, increased body fat, low mood, poor concentration, reduced body hair and, over time, reduced bone density.

These are non-specific, which is why diagnosis requires blood tests and not symptoms alone.

How it is properly diagnosed

At least two morning samples, taken fasting, on separate days, because levels are highest in the morning and vary considerably day to day.

A single afternoon sample is not adequate for diagnosis, and a great deal of prescribing rests on exactly that.

Additional tests are needed to distinguish primary from secondary — luteinising hormone, follicle stimulating hormone, prolactin — because the cause changes the management, and a pituitary tumour is not treated by giving testosterone.

Sex hormone binding globulin and calculated free testosterone matter where total levels are borderline, particularly in obesity and older age.

Reversible causes worth addressing first

Frequently ignored in favour of a prescription.

Obesity, where weight loss raises testosterone measurably and where the relationship is bidirectional.

Obstructive sleep apnoea, which suppresses it and which is common in exactly the population being prescribed to.

Opioid use, which is a potent and reversible suppressor.

Excess alcohol.

Anabolic steroid use, past or present, which suppresses natural production and sometimes permanently.

Chronic illness and acute illness, which lower levels transiently.

And chronic sleep deprivation, where experimental restriction produces measurable falls in a week.

Treatment and its consequences

Where genuine deficiency is confirmed, replacement improves libido, mood, body composition and bone density with reasonable evidence.

It also has consequences that must be disclosed and frequently are not.

It suppresses sperm production, sometimes profoundly and occasionally irreversibly, which makes it inappropriate for any man who may want children — alternative treatments exist that preserve fertility.

It requires monitoring of haematocrit, since it stimulates red cell production and can thicken the blood.

It requires prostate monitoring in accordance with local guidance.

It is generally lifelong once started, because the axis is suppressed by the treatment itself.

And cardiovascular safety has been the subject of considerable debate, with a large recent trial providing more reassurance than earlier signals suggested while not settling every question.

The clinic model

Worth being direct about.

Online and storefront services offering testosterone with minimal assessment, single afternoon samples, no investigation of cause, and a subscription model have expanded rapidly.

They typically do not exclude pituitary disease, do not discuss fertility adequately, do not address reversible causes, and have a financial interest in the answer being yes.

A man with genuine deficiency deserves proper diagnosis and long-term monitoring; a man with normal levels and fatigue deserves an investigation of why he is tired, which is a different and more useful appointment.

In women

A narrower picture.

Testosterone has evidence for improving low sexual desire in postmenopausal women with distressing loss of libido, and international consensus supports its use in that specific indication.

Products licensed for women are unavailable in many countries, so male preparations are used at reduced doses under specialist supervision.

Evidence does not support its use for fatigue, mood or general wellbeing in women, which is nonetheless how it is frequently marketed.

General information only, not medical advice. Consult a qualified clinician about symptoms — do not obtain testosterone without proper diagnosis and monitoring.