Testosterone begins with the pituitary gland. The LHLH hormone there prompts the testicles to produce it, according to the U.S. National Library of Medicine's MedLine Plus website. MayoClinic.com says that production peaks in the teenage years and remains high through your 20s, but then levels begin declining at the rate of about 1 percent a year.
Components
There are two components to testosterone, serum levels and "free" or "unbound" testosterone, says Dr. Edward Lichten. Unbound testosterone is bioavailable and affects muscle mass and the body's tissues, according to MedLine Plus. Lichten says that total testosterone is not as important as free testosterone levels.
Range
Normal levels of testosterone can range from as low as 350 ng/dl to 1,200 ng/dl or nanograms per deciliter. Lichten says that as many as half of all men at age 40 have levels below 450 ng/dl. Your level is highest in the morning and declines as the day goes on due to factors such as stress or exercise.
Role
Testosterone is not just a sex-drive hormone, according to MayoClinic.com. At normal levels, it also plays a part in sperm production, bone density, muscle mass, red blood cell production and your body's distribution of fat. In teenage boys, it prompts the voice to deepen, stronger bones to build and the growth of facial and body hair, according to Health Press, an online collection of articles pertaining to health issues.
Changes
Although age is the most common cause of dropping testosterone levels, chronic illness, hypopituitarism and testicular failure can all cause your testosterone level to drop below normal, as well, according to MedLine Plus. Lichten says that when there is a significant downward change in your testosterone level, you may be at risk for stroke, heart attack, prostate cancer, osteoporosis and dementia. MayoClinic.com reports that you might also experience less sexual desire and occasional erectile dysfunction if your testosterone level falls below the norm, as well as insomnia, more body fat and less muscle bulk. Levels lower than normal can also cause mood disturbances like depression.
Maintenance
Health Press indicates that lifestyle changes can help maintain normal testosterone levels as you age. The website recommends eating a diet high in proteins and low in carbohydrates. If you smoke, stop. If you drink alcohol, keep to moderate consumption. You can also ask your doctor about available herbal or natural supplements. According to MayoClinic.com, if a low testosterone level is causing you health problems, you should speak to your doctor because there are several hormone replacement therapies available, as well.
