What causes low testosterone?

Testosterone production depends on signals between the brain, pituitary gland and testes. A problem at any point can reduce production. Testicular injury, infection, some genetic conditions and treatments affecting the testes are possible causes. Medicines such as opioid painkillers or corticosteroids may suppress hormone signalling. Obesity can alter hormone balance, while type 2 diabetes may be associated with reduced testosterone. Age-related change, severe illness, poor nutrition and inadequate sleep can also influence results, but one low test does not establish a diagnosis.

Tell a clinician about reduced sexual desire, erection changes, low energy, fertility concerns, testicular symptoms, medicines and other illnesses. Diagnosis usually combines symptoms with repeat early-morning blood tests, because levels vary during the day. The clinician may check related hormones and investigate an underlying cause. Do not start testosterone products without assessment: treatment can affect fertility and may be unsuitable for some people.

Arrange an appointment for persistent symptoms, fertility difficulty, breast enlargement, reduced shaving or body hair, or a change in testicular size. Seek prompt care for sudden severe testicular pain, marked swelling, or symptoms after an injury. A sudden change in sexual function with severe headache or vision problems also needs urgent assessment because it can point to a problem affecting hormone control.

Do my symptoms and repeat morning tests support low testosterone? Could my medicines, weight, diabetes or another illness contribute? Should fertility be protected before considering treatment?