Hypogonadism (Low Testosterone)

Hypogonadism is when the body's sex glands produce too little sex hormone. In men this often centres on low testosterone, a hormone important for many functions beyond reproduction. Diagnosis combines symptoms with carefully timed blood tests, because a single low reading is rarely enough on its own.

What hypogonadism is

Testosterone is the main male sex hormone, made chiefly in the testes under the control of signals from the brain. The hypothalamus releases gonadotropin-releasing hormone, which prompts the pituitary gland to release luteinising hormone (LH) and follicle-stimulating hormone (FSH); these in turn drive the testes to make testosterone and sperm. Testosterone supports muscle and bone, sex drive, mood, energy, and the production of red blood cells. This signalling chain is often called the hypothalamic-pituitary-gonadal axis, and it works as a feedback loop: when testosterone is adequate, the brain eases off its signals, and when testosterone falls, the brain normally sends stronger signals to restore it.

Hypogonadism is usually divided into two types based on where the chain breaks down. In primary hypogonadism the problem is in the testes themselves, so testosterone is low while LH and FSH are high as the body tries to compensate. This pattern is sometimes called hypergonadotropic hypogonadism. In secondary hypogonadism the problem lies higher up, in the pituitary or hypothalamus, so testosterone is low and LH and FSH are low or inappropriately normal; this is sometimes called hypogonadotropic hypogonadism. A third pattern combines features of both and can appear with ageing or chronic illness. Distinguishing these helps point to the cause and shapes any further testing.

Although hypogonadism is most often discussed in men, the underlying idea applies to anyone whose gonads underproduce sex hormones. In women the corresponding picture involves the ovaries and oestrogen, which is addressed in separate menopause and ovarian topics. This page focuses on testosterone deficiency, the form most commonly described as hypogonadism.

Common signs and symptoms

Low testosterone can produce a range of symptoms that develop slowly and overlap with everyday life stresses, which is part of why it can be easy to miss. People may notice:

• Reduced sex drive
• Erectile difficulties
• Persistent fatigue and low energy
• Low mood, irritability, or difficulty concentrating
• Loss of muscle bulk or strength
• Increased body fat
• Reduced body or facial hair
• Hot flushes or sweats when levels fall sharply
• Over the longer term, thinning bones

When hypogonadism is present from before or during puberty, the picture can differ, with delayed or incomplete development of adult sexual characteristics. In adults who develop it later, the changes are usually more subtle and gradual. Because the symptoms are non-specific, their presence alone does not confirm the diagnosis.

What causes it

Causes vary by type. Primary hypogonadism can follow injury to the testes, certain genetic conditions, mumps affecting the testes, some cancer treatments such as chemotherapy or radiation, or undescended testes. Secondary hypogonadism can result from pituitary problems such as a benign tumour, certain medicines, significant obesity, chronic illness, sleep disorders, or other hormonal conditions including a raised prolactin level.

Testosterone also declines gradually with age in many men. This age-related fall differs from a distinct medical condition and is interpreted by a clinician alongside symptoms, because a modest decline is a normal part of ageing for many people. Acute or severe illness can temporarily lower testosterone as well, which is one reason testing is generally avoided during an acute illness and confirmed once a person has recovered.

How it is diagnosed

Diagnosis rests on both symptoms and blood tests, since neither alone is sufficient. Testosterone follows a daily rhythm and is generally highest in the morning, so testing is usually done on a morning sample, and a low result is typically confirmed with a repeat test on a separate morning. Common tests include:

• Total testosterone — the standard starting measurement, drawn in the morning, ideally when a person is otherwise well.
• Free or calculated testosterone — sometimes added when binding proteins may be skewing the total, for example in obesity or with age.
• LH and FSH — help separate primary from secondary causes.
• Other markers — such as prolactin, iron studies, or thyroid tests, to look for contributing conditions.

The table below shows illustrative ranges only. Actual ranges vary by laboratory, age, and the assay used, so always interpret results with a clinician.

For more on the hormone and the test itself, see our hormones and blood tests sections, and the related conditions in our conditions overview.

How it is generally managed

Management begins with identifying and addressing any underlying cause, such as a pituitary problem, a contributing medicine, or factors like significant obesity or untreated sleep apnoea that can lower testosterone. Where appropriate, clinicians may discuss testosterone replacement to relieve symptoms, weighing potential benefits against risks for the individual. This decision is personal and depends on the cause, symptoms, fertility goals, and overall health, and it includes ongoing monitoring with blood tests. General treatment principles are outlined in our treatments section. This page is educational and does not recommend any specific treatment.

Complications and when to seek care

Long-standing untreated testosterone deficiency can contribute to reduced bone density and, over time, a higher chance of fracture, which links hypogonadism to osteoporosis. It may also affect mood, energy, and quality of life. Anyone with persistent symptoms such as low libido, ongoing fatigue, or erectile difficulties is encouraged to seek assessment rather than self-diagnosing, because the symptoms can also signal other treatable conditions. Sudden or severe symptoms, or signs that might suggest a pituitary problem such as new persistent headaches or vision changes, warrant prompt medical attention.

Living with hypogonadism

For many people, general health measures support overall wellbeing alongside any medical care: regular physical activity including resistance exercise, a balanced diet, adequate sleep, and limiting alcohol. Where treatment is started, attending follow-up appointments and blood tests helps a clinician keep care appropriate and watch for any effects. Because the condition and its management are individual, ongoing conversation with a healthcare professional is the most reliable guide.