The testes (testicles) in men serve two main functions:
Testosterone production is controlled by the pituitary gland. The pituitary produces two hormones, called luteinizing hormone (LH) and follicle stimulating hormone (FSH), which stimulate the testes to produce testosterone and sperm. In turn, the pituitary can sense the level of testosterone and regulate the LH and FSH to maintain normal levels.
Symptoms of low testosterone include:
Young men or boys with low testosterone during their teens may fail to go through puberty normally. Infertility can occur with low testosterone. Over time, low testosterone can cause weakness in the bones (osteoporosis).
WHAT CAUSES LOW TESTOSTERONE?
Low testosterone can be caused by aging, obesity, problems with the testes or problems with the brain or pituitary gland.
1. The main causes of low testosterone are aging and obesity.
2. Testicular problems. These include damage from injury, infection or medications (such as chemotherapy), and certain inherited genetic abnormalities, such as a condition called Klinefelter’s syndrome.
3. Brain/pituitary problems. Potential problems include benign pituitary tumors, other tumors/growths near the pituitary, pituitary inflammation, high iron levels, and medications.
HOW IS LOW TESTOSTERONE EVALUATED?
An evaluation of low testosterone will try to answer three main questions:
Is testosterone low?
Testosterone levels are variable from day-to-day and levels change throughout the day, particularly in younger men. Levels are highest in the morning, which is when testosterone should ideally be measured (8 to 10 a.m.).
Why is testosterone low?
Once testosterone is confirmed to be low, the next step is to try and understand why this has occurred. Measurements of LH and FSH will show if the problem originates with the testicles (LH/FSH levels elevated) or the problem originates with the brain/pituitary (LH/FSH not elevated). If the lab values indicate a problem with the brain or pituitary, your doctor may ask you to have a pituitary MRI scan. Additionally, blood testing for prolactin and iron may be needed.
How should testosterone be treated?
If the cause of low testosterone cannot be fixed, which is common, testosterone therapy should be considered.
WHAT ARE THE RISKS OF TESTOSTERONE THERAPY?
Testosterone therapy is generally safe and well-tolerated, but there are potential problems that can occur. Potential problems are summarized below:
If any of these problems occur (or if you have other problems that you think are related to testosterone), you should discuss these with your doctor.
HOW WILL I BE MONITORED WHEN TAKING TESTOSTERONE?
When taking testosterone, your health care provider will ask you to come to the clinic periodically to discuss symptoms and potential side effects and to perform a physical exam. Periodically, blood testing will be needed to measure your testosterone level, with the goal typically to have a level into the middle of the normal range.