Low testosterone can cause an obvious lack of male characteristics, or it can cause vague symptoms such as fatigue and diminished sex drive.
The symptoms of low testosterone (or “low T”) in males can vary depending on the cause of the low level and the age at which it occurs.
In male hypogonadism, a condition in which the body is unable to produce normal amounts of the hormone testosterone, symptoms may include underdeveloped genitalia, delayed puberty, and a lack of secondary sexual characteristics such as a deeper voice and facial hair.
In middle-aged or older men experiencing age-related decreases in testosterone, symptoms may include low energy, depressed mood, low sex drive, and erectile dysfunction (ED or impotence).
No matter what the cause, symptoms alone are not enough for a diagnosis of low testosterone: A blood test is needed to confirm that a man’s testosterone level is, indeed, low.
Symptoms of Hypogonadism
Male hypogonadism can occur at any age, as a result of problems affecting the testicles or the pituitary gland.
Signs of hypogonadism in infants include:
- Ambiguous genitalia
- Female genitalia (in a genetically male child)
- Underdeveloped male genitalia
In boys, hypogonadism is associated with delayed puberty and can cause symptoms such as:
- Lack of development of muscle mass
- No deepening of the voice or growth of body hair
- Slow increase in size of penis or testicles
- Arms and legs that grow out of proportion to the rest of the body
In adult men, symptoms of hypogonadism include:
- Lack of fertility
- Low sex drive
- Erectile dysfunction
- Sparse facial or body hair
- Growth of breast tissue
Blood testosterone levels in men with hypogonadism are very low and do not fluctuate from day to day, the way they do in healthy men.
Symptoms of Age-Related Testosterone Decline
Low testosterone in men can also cause nonspecific symptoms such as:
- Sleep disturbances
Not all men with age-related low testosterone have — or are bothered by — symptoms. In addition, the level at which symptoms occur varies from man to man.
Nonspecific signs and symptoms such as fatigue, sleep problems, and low mood can also be caused by other factors such as medication side effects, depression, and excessive alcohol use.
Symptoms of Low Testosterone in Women
Women also produce testosterone — in the ovaries and adrenal glands — and they also experience a normal drop in testosterone levels in the time leading up to menopause.
This drop may be associated with a decrease in libido (sex drive), low energy, persistent fatigue, and depressed mood.
Hypogonadism and age-related low testosterone are diagnosed with blood tests that measure the level of testosterone in the body.
The Endocrine Society and the American Association of Clinical Endocrinologists recommend testing for suspected low T with a total testosterone test performed in the morning (when testosterone levels tend to be highest in young men, although this isn’t necessarily the case in older men).
The test is often repeated on another day if the results show a low T level.
Sometimes a test for “free” or “bioavailable” testosterone is also performed.
The majority of testosterone in the blood is bound to one of two types of protein — either albumin or sex hormone binding globulin (SHBG) — while a small percentage is unbound, or free.
The portion of testosterone that is bound to SHBG is biologically inactive but, because the bonds between testosterone and albumin are weaker than those between testosterone and SHBG, the portion bound to albumin is biologically active.
Bioavailable testosterone therefore includes free testosterone and albumin-bound testosterone.
A number of medical conditions and medications can raise or lower the amount of SHBG in the blood, consequently altering the amount of bioavailable testosterone.
In those situations, measuring the amount of bioavailable testosterone gives a more accurate indication of the amount of biologically active testosterone in a person’s system.