Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.
Ruchi Mathur, MD, FRCP(C) is an Attending Physician with the Division of Endocrinology, Diabetes and Metabolism and Associate Director of Clinical Research, Recruitment and Phenotyping with the Center for Androgen Related Disorders, Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center.
Low testosterone levels may be caused by a number of factors. For example –
there may be a problem at the level of the hypothalamus or pituitary to produce
appropriate amounts of LH and FSH to stimulate testosterone production. Another
possibility is that the organs that make testosterone do not function normally
or are not able to respond to stimulation by the brain. Also, as mentioned,
changes in SHBG can affect for the amount of testosterone that is available to
exert its effects.
When the problem is in the organs that produce testosterone (the ovaries or
testes, for the most part), it is called a "primary" problem". In medical
terminology, the decrease in normal testosterone production is called "hypogonadism."
When the problem is related to the pituitary and its ability to
regulate testosterone, it is called "secondary hypogonadism," and
If the problem
is thought to be at the level of the hypothalamus, it is called "tertiary
Some common causes of primary hypogonadism or failure of the gonads (the
medical term for the sex organs, or testes and ovaries) may include the
Undescended testicles: If the testes fail to migrate from inside the
abdomen into the scrotum during fetal development or in the first year or two of
life, the testes may become damaged and unable to produce adequate amounts of
Injury to the scrotum: If the testes are injured, they may not be able to
produce adequate testosterone. Damage to one testicle does not often to lead to
low levels if the other testis remains normal.
Cancer therapy:Chemotherapy and
radiation therapy can damage the
interstitial cells in the testes responsible for testosterone production. This
decrease in testosterone production may be temporary as the cells recover, or it
may be permanent.
Aging: Testosterone levels gradually decrease with aging. Usually, enough
testosterone is manufactured to allow for adequate bodily functions, but there
is some research that suggests that lower testosterone levels can result in
a variety of medical problems such as bone and muscle loss, and erectile
Mumps orchitis: The
mumps virus can cause inflammation of the testes in
males, and if the illness occurs in
puberty or adulthood, the damage to the
testes may lead to low testosterone production.
Immunization against the
significantly decreased the incidence of this illness.
Chromosomal abnormalities: A normal male has one X and one Y chromosome (a
normal female has two X chromosomes). In
in males, an extra X
chromosome is present and among other anatomic issues, there is abnormal
development of the testes and decreased ability to manufacture testosterone.
HIV and AIDS may also cause inflammation of both the
hypothalamus and pituitary.
Illegal use of anabolic steroids, for example in
athletes and body builders, can cause hypogonadism and low testosterone levels.
It should be noted that obesity also can be a cause of low testosterone.
While it can be associated with other causes, obesity specifically enhances the
conversion of testosterone to estrogen. This is a naturally occurring process in
both men and women, and this conversion occurs predominantly in fat cells. In
the case of obesity, the large amount of fat cells enhances this process, and
testosterone levels may fall due to excessive conversion to estrogen.
There are rarer causes of hypogonadism that can occur, dealing with cellular
mechanisms and receptor binding. These are beyond the scope of this discussion.