Testosterone deficiency, or male hypogonadism, is a condition where the serum testosterone levels are below normal. Testosterone is produced by the Leydig cells in the testicles and is regulated by hormones produced in the hypothalamus/pituitary gland axis. (LH and FSH). Testosterone plays an important role in male sexual and physical development and also maintains energy levels, fertility, sex drive, and bone health in adults. Some decline in testosterone production is normal as men age. When low testosterone become symptomatic then treatment, usually replacement with supplemental testosterone, may be effective.

Types

Male hypogonadism can be primary or secondary. Primary hypogonadism is a condition where the testes do not make adequate testosterone although the releasing hormones from the brain are normal. This could be caused by injury, disease or other factors affecting the testes. Secondary hypogonadism results from disorders or injuries affecting the centers in the brain that control hormone production (hypothalamus or pituitary gland).

Risk Factors

Testosterone deficiency can be caused by:

  • Chemotherapy or radiation therapy
  • Aging — about 30% of men older than 75 experience low testosterone levels
  • Obesity
  • Type II diabetes
  • 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
  • HIV/AIDS
  • Some inflammatory disorders such as tuberculosis or sarcoidosis

Symptoms

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 (present at birth) 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.

Diagnosis

Blood tests can determine the level of testosterone and or brain hormones in your bloodstream. Testing is usually done in the morning when testosterone levels are highest.