Low Testosterone
Medical Author:
Benjamin C. Wedro, MD, FACEP, FAAEM
Medical Editors:
Ruchi
Mathur, MD, FRCP(C) and
Melissa Conrad Stöppler, MD
Low Testosterone Symptoms
Low Testosterone Symptoms in Men & Women
Symptoms of low testosterone in males depends upon when the low levels occur. In men, low testosterone may lead to:
- infertility,
- decrease sexual function and desire,
- erectile dysfunction (ED),
- hair loss,
- decreased muscle mass, and
- osteoporosis.
Symptoms of low testosterone levels in women include:
- hot flashes,
- irritability,
- loss of sexual desire,
- sleep disturbances,
- loss of muscle mass, and
- decreased bone density (osteoporosis).
What is testosterone?
Testosterone is a steroid hormone which is made in the testes in males and in
the ovaries in women (a minimal amount is also made in the adrenal glands).
Testosterone has two major functions in the human body.
- Testosterone is needed
to form and maintain the male sex organs and promote secondary male sex
characteristics (in both men and women) such as voice deepening and hair growth
patterns. This function is related to its androgenic properties.
- Testosterone is the facilitation of muscle growth as well as bone
development and maintenance. This is a result of its anabolic properties.
Testosterone production is regulated by hormones released from the brain. The
hypothalamus and pituitary gland located in the brain produce hormonal signals
that ultimately result in the production of testosterone. The hypothalamus is
located just above the brain stem, and among its many functions, it produces
gonadotrophin releasing hormone (GRH). GRH then travels a short distance to the
pituitary gland, which is located in the base of the brain, and stimulates this
gland to release FSH (follicle stimulating hormone) and LH (luteinizing
hormone). These hormones travel through the bloodstream to activate the sex
organs in both men and women. Subsequently, these hormones have a role in
regulating testosterone levels in the bloodstream.
The majority of testosterone circulates in the blood bound to a carrier
protein (many hormones that are produced in one area and affect another area
have a carrier protein that helps their travel through the bloodstream). In this
case the carrier protein is called "sex hormone binding globulin," or SHBG. When
testosterone is being carried by SHBG, it is considered "bound". Bound
testosterone does not play an active role in the body; only the unbound or "free" testosterone is able to enter the different cells of the body and exert
its androgenic and anabolic effects. Thus, anything that affects the function or
the amount of SHBG can also affect the total circulating amount of active
testosterone.
What is low testosterone?
The human body functions within a relatively narrow range of normal. When
chemicals such as hormones fall outside those normal levels, there can be
consequences that affect the body at a cellular, organ, or systemic (body-wide)
level.
Blood tests used to measure testosterone are usually performed in the morning.
Testosterone sampling is difficult since the levels normally tend to bounce
around a fair bit during the course of the day. The normal value for total
testosterone in males is 270-1070 ng/dl. However, this depends to some extent
on the individual laboratory being used, and the range can vary as a result. In
women, there is debate about the accuracy of testosterone measurements, because
the circulating values are so much lower than in males and are harder to
accurately measure.
With advancing age, in both men and women, the amount of testosterone the
body produces gradually falls. Free testosterone levels can be measured and
normal levels depend upon an individual's age. Interestingly,
menopause
itself does not seem to play a role in a reduction of testosterone levels in
women beyond that of advancing age.
Next: What are the causes of low testosterone? »
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