Low testosterone rarely traces back to one tidy cause. This page sorts the causes the Endocrine Society lists, so you can tell which ones are worth mentioning at a visit.
Where the problem starts
The Endocrine Society says hypogonadism has many causes, and that they may involve a problem with the testes or with the signal from the brain that controls testosterone secretion. For treatment, see the Endocrine Society's statement on testosterone replacement therapy.
Causes tied to an injury, a treatment or a medication
The Endocrine Society lists testicular injury, including trauma and castration, and testicular infection as causes of low testosterone. It also lists radiation or chemotherapy treatment for cancer. Some medications appear too, such as opiate painkillers and corticosteroids like steroid injections, along with anabolic steroid use.
Causes tied to a disease or a hormone disorder
The Endocrine Society names hormone disorders, including pituitary tumors or diseases and high levels of prolactin. It also names chronic diseases: HIV/AIDS, type 2 diabetes, sleep disorders, obesity, and liver and kidney disease. The Endocrine Society's guide to hypogonadism in men carries the full list.
Causes written into your genes
The last group on the Endocrine Society's list is a genetic condition, with Klinefelter syndrome, hemochromatosis and Kallmann syndrome as examples. A narrative review of testosterone therapy in men aged 50 and above in PMC looks at the evidence for that age group.
The first step
A list of causes cannot tell you which one applies to you. If you take one of the medications above or live with one of the conditions, mention it when you describe your symptoms to a clinician. MedlinePlus explains the testosterone levels test that measures the hormone itself.