Testosterone is the male sex hormone that is made in the testicles. Testosterone hormone levels are important to normal male sexual development and functions.

During puberty (in the teen years), testosterone helps boys develop male features like body and facial hair, deeper voice, and muscle strength. Men need testosterone to make sperm. Testosterone levels generally decrease with age, so older men tend to have low blood testosterone levels.

Some men have low testosterone levels. This is called Testosterone Deficiency Syndrome (TD) or Low Testosterone (Low-T). Deficiency means that the body does not have enough of a needed substance. Syndrome is a group of symptoms that, together, suggest a disease or health condition.

The American Urology Association (AUA) identifies low blood testosterone (Low-T) as less than 300 nanograms per deciliter (ng/dL). These symptoms or conditions may accompany Low-T:

• Low sex drive
• Fatigue
• Reduced lean muscle mass
• Irritability
• Erectile dysfunction
• Depression
• There are many other possible reasons for these symptoms, such as: opioid use, some congenital conditions (medical conditions you are born with), loss of or harm to the testicles, diabetes, and obesity (being overweight). See your doctor if you have any of these symptoms.

Symptoms

There are many signs and symptoms of Low Testosterone. Some are more closely related to Low-T levels (specific signs and symptoms). Others may not necessarily be linked (non-specific signs and symptoms). Your doctor will help you make sense of your own situation.

Low sexual desire alone may not mean that you have TD. But if you have a combination of low sexual desire, reduced erectile function, and feelings of sadness and tiredness, you should talk to your doctor.

Causes

Some persons are born with conditions that cause Testosterone Deficiency (TD) such as:

• Klinefelter syndrome
• Noonan syndrome
• Ambiguous genitalia (when the sex organs develop in ways that are not typical looking)

Some men may develop Low-T because of conditions like these:

• Damage to testicles by accident
• Removal of testicles because of cancer
• Chemotherapy or radiation
• Pituitary gland disease leading to hormone deficiency
• Infection
• Autoimmune disease (when the body makes antibodies that attack its own cells)