What is testosterone?
How does the body know how much testosterone to make and release?
What is a “normal” level of testosterone?
Why would a doctor suspect that someone has a low level of testosterone?
Can low testosterone be seen in younger men too?
Can a low testosterone level cause other problems?
If someone has a low testosterone level, how do they get it increased?
What are the next steps for a man who has low testosterone?
What is testosterone?
Testosterone is the primary sex hormone produced in men’s bodies. Testosterone stimulates the development of the penis and testes, growth of facial and pubic hair, deepening of the voice, changes in body-shape, growth of bones, and increased muscle mass and strength. It helps maintain sex drive and the production of sperm cells, and it may play a role in balding. Mood is also affected by testosterone, and low levels of the hormone can cause severe and prolonged depression as well as fatigue. Testosterone is produced mostly in the testes and a small amount is produced from steroids secreted from the outer part of the adrenal glands called the adrenal cortex. Women’s ovaries also produce a small amount of testosterone.
How does the body know how much testosterone to make and release?
The testes receive chemical signals from the pituitary gland, which is located at the base of the brain. The pituitary gland receives signals from the hypothalamus. The hypothalamus secretes gonadotropin-releasing hormone (GnRH). This signals the pituitary gland to produce and secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). LH signals the testes to produce testosterone. If the testes begin producing too much testosterone, the body sends signals to the pituitary telling it to make less LH. This, in turn, slows down the production of testosterone.
What is a “normal” level of testosterone?
Doctors check to see if a man’s blood testosterone level falls into a generally acceptable range of values. Testosterone levels vary from hour to hour, so fluctuations can be seen in men with no apparent problems. Generally, the highest testosterone levels occur in the early morning hours, so measurements should be taken at this time. Normal ranges are determined in normal, healthy men between the ages of 20 and 40 or 45. How is testosterone measured?
If a doctor suspects someone is not producing enough testosterone, he/she will check if the total blood testosterone level falls into the acceptable range. The doctor also may instruct the laboratory to measure the amount of free or loosely bound testosterone (about 40 percent of the total testosterone is strongly bound to a protein called sex hormone binding globulin, known as SHBG; about 58 percent is weakly bound to another protein called albumin) and the amount of free testosterone (only about two percent circulates freely in the blood). Blood levels of SHBG increase with age, so older men may have a higher percentage of bound testosterone and a lower percentage of free testosterone. Bioavailable testosterone includes the non-SHBG bound testosterone or the sum of the testosterone, which is bound to albumin and free (unbound) testosterone. How does aging affect the body’s ability to make testosterone?
Not only does the amount of testosterone produced decline with age, the morning spike of testosterone seen in young men is blunted in older men. The pituitary glands of older men also may produce less luteinizing hormone (LH), which decreases testosterone production. Testosterone in aging men is more likely to bind to sex hormone binding globulin (SHBG), which reduces the amount of bioavailable or freely circulating testosterone that is available to the body. However, aging also is frequently associated with increasing obesity, and obesity is associated with decreased SHBG levels. Thus, measurement of non-SHBG bound testosterone may be needed in aging, obese men.
Why would a doctor suspect that someone has a low level of testosterone?
Symptoms related to low testosterone include: decreased sex drive, erectile dysfunction (ED), lowered sperm count, increased breast size (a condition called gynecomastia), hot flashes, increased irritability, trouble concentrating, and depression. Men who have a severe and prolonged reduction of testosterone also may experience loss of body hair, reduced muscle mass and bone fractures due to osteoporosis. Certain medical conditions also can cause the condition.
Can low testosterone be seen in younger men, too?
Yes. Certain genetic conditions such as Klinefelter’s syndrome, Kallmann’s syndrome, and Prader-Willi syndrome can cause lowered testosterone production in boys and young men. In addition, testosterone production can be lowered by bilateral cryptochid testes injury, inflammation, and tumors. Chemotherapy and radiation therapy also may damage testosterone-producing cells. Finally, many patients who are HIV+ have low testosterone levels.
Can a low testosterone level cause other problems?
Studies have shown that men with low testosterone can become frail, lose muscle mass and suffer bone fractures due to osteoporosis. Some data have suggested that testosterone therapy can lead to increases in muscle mass and strength. Researchers also have shown that men who are testosterone-deficient may be more likely to experience depression and reduced quality-of-life than men who produce adequate amounts of the hormone.
If someone has a low testosterone level, how do they get it increased?
Supplemental preparations of testosterone currently are available in gel and patch forms that deliver it through the skin, as pills, or as preparations that have to be injected into deep muscle about every 7 to 21 days.
What is the next step for a man who has low testosterone?
An endocrinologist is a doctor who is a medical expert in treating diseases with abnormal hormone secretion and tumors of glands that secrete hormones. Board-certified endocrinologists are ideally suited to evaluate, diagnose, and identify a wide spectrum of medical, physical and psychiatric abnormalities responsible for causing male sexual dysfunction including a low testosterone level. To find an endocrinologist near you, visit The Hormone Foundation’s “Find an Endocrinologist” physician referral directory at www.hormone.org (The directory is comprised of over 2,500 members of The Endocrine Society, the parent organization of The Hormone Foundation and the largest organization of endocrinologists in the world.)