Male Hypogonadism (Low Testosterone)

Male hypogonadism occurs when the testes do not produce enough testosterone and/or when the hormonal system controlling the testes does not function normally.

Testosterone is the principal male sex hormone. It contributes to sexual desire, erectile and reproductive function, sperm production, muscle and bone health, red blood cell production, body composition, and the development and maintenance of male secondary sexual characteristics.

Low testosterone on a blood test alone does not necessarily mean that a man has clinical hypogonadism. Testosterone levels can vary because of the time of day, illness, medications, obesity, nutritional factors, and other health conditions.

For this reason, male hypogonadism is generally diagnosed when a man has symptoms or signs consistent with testosterone deficiency together with consistently low testosterone concentrations confirmed by appropriate testing.

Why testosterone can become low

The male reproductive hormonal system works through the hypothalamic-pituitary-gonadal axis.

The hypothalamus signals the pituitary gland, which releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH stimulates the Leydig cells in the testes to produce testosterone, while FSH plays an important role in sperm production.

A problem at the level of the testes can therefore cause testosterone deficiency. Alternatively, the testes may be capable of functioning normally but receive insufficient hormonal stimulation because of a disorder affecting the hypothalamus or pituitary gland.

Distinguishing between these causes is important because treatment — particularly in men who want to preserve or restore fertility — may be very different.

Low testosterone and male fertility

Testosterone deficiency and male infertility can occur together, but they are not the same condition.

Men who want children should tell their doctor about their fertility plans before beginning treatment. External testosterone therapy can suppress LH and FSH signaling to the testes and may substantially reduce sperm production.

For men with certain forms of secondary hypogonadism who wish to achieve fertility, treatment aimed at stimulating the testes may be considered instead of conventional testosterone replacement.

Is low testosterone simply part of ageing?

Testosterone levels can decline as men grow older, but ageing alone does not establish a diagnosis of hypogonadism.

Symptoms such as fatigue, reduced sexual desire, erectile difficulties, changes in mood, or reduced physical performance can have many other causes.

A diagnosis should therefore be based on the combination of symptoms, clinical assessment, and appropriately confirmed hormone levels rather than age alone.

Diagnosis starts with a detailed medical and sexual history. The doctor may ask about libido, erections, fertility, energy levels, medications, previous illnesses, testicular problems, cancer treatments, anabolic steroid exposure, and plans for future children.

A physical examination may assess the testes, body hair, breast tissue, body composition, and other signs that could suggest androgen deficiency or an underlying hormonal disorder.

Testosterone blood testing

Testosterone should usually be measured in the early morning, when concentrations are normally highest.

A low result should generally be confirmed with a second early-morning measurement rather than diagnosing hypogonadism from a single test.

Depending on the clinical situation, testing may include:

• Total testosterone

• Free testosterone or calculated free testosterone when indicated

• Sex hormone-binding globulin (SHBG)

• Luteinizing hormone (LH)

• Follicle-stimulating hormone (FSH)

• Prolactin

LH and FSH are particularly useful for distinguishing primary testicular hypogonadism from secondary hypothalamic or pituitary hypogonadism.

Additional investigations may be required depending on the suspected cause. These can include thyroid or other hormone tests, iron studies, semen analysis when fertility is relevant, genetic testing, bone-density assessment, or pituitary imaging in selected patients.

The goal is not simply to identify a low testosterone number, but to determine whether true hypogonadism is present and why it has developed.