Testosterone deficiency, or male hypogonadism, results when the body does not produce enough of the male sex hormone testosterone. Testosterone deficiency can occur at birth (congenital), during puberty or during adulthood. Millions of American men experience this condition, often after age 50, when testosterone production declines.

Testosterone is produced by the testes and regulated by hormones in the hypothalamus and pituitary gland. It plays an important role in male sexual and physical development and also maintains energy levels, fertility, sex drive and bone health in adults.


Male hypogonadism can be primary or secondary. Primary hypogonadism is caused by injury, disease or another factor affecting the testes. Secondary hypogonadism results from disorders or injuries affecting the hypothalamus or pituitary gland in the brain.

Risk Factors

Testosterone deficiency can be caused by:

  • Chemotherapy or radiation therapy
  • Aging - about 30% of men older than 75 experience low testosterone levels
  • Infections such as meningitis, syphilis, mumps
  • Undescended testes
  • Klinefelter's syndrome (an extra X chromosome causes underdeveloped testes)
  • Damage to the testes or brain caused by injury, tumors or surgery
  • Kallman syndrome - abnormal hypothalamus development
  • Some inflammatory disorders such as tuberculosis or sarcoidosis


Adult-onset hypogonadism can produce one or more of these symptoms:

  • Decreased libido (sex drive)
  • Erectile dysfunction (impotence)
  • Growth in breast tissue (gynecomastia)
  • Infertility
  • Muscle weakness or fatigue
  • Bone loss
  • Diminished growth or loss of body hair
  • Depression or other mood disorders

Congenital hypogonadism can cause undeveloped, ambiguous or underdeveloped genitalia. Onset during puberty can prevent normal male adolescent development, such as deepening of the voice, hair growth, and muscle and sex organ development.


Blood tests can determine the level of testosterone in your blood stream. These are usually taken in the morning, when testosterone levels are highest. If you have low levels of testosterone, your doctor may order:

  • Hormone tests
  • Semen analysis
  • Imaging tests of the pituitary

Your doctor may perform a testicular biopsy if other tests determine that you are not producing any sperm.


Primary hypogonadism often is treated with testosterone replacement therapy (TRT). The testosterone can be delivered through a number of different methods, each of which is usually effective at reducing symptoms and improving your energy and feeling of well-being. Cost, side effects and personal preference may determine which of the following is best for you:

  • A patch - you apply a patch containing testosterone to your skin each night, rotating between several different areas to lessen skin irritation.
  • A gel - the testosterone is absorbed through the skin of your abdomen or upper arms as the gel dries. This method may lessen skin irritation but you must avoid bathing and contact with others until the gel is dried.
  • A tablet that dissolves in the mouth (buccal cavity) - a small, putty-like substance is inserted between your gums and upper lip. It dissolves and is absorbed into your blood stream. Side effects can include mouth irritation, pain, bitter taste and headaches.
  • Intramuscular injection - typically given every two weeks at home or in the doctor's office. Family members can learn to give the injections. Safe and effective, but testosterone levels may fluctuate between injections.

Oral testosterone is no longer prescribed due to its association with severe liver problems and other difficulties.

Secondary hypogonadism that is caused by pituitary disorders may be treated with pituitary hormones. A pituitary tumor may be treated surgically or with radiation or medication.