Slideshow: A Visual Guide to Low Testosterone

Testosterone may be the most notorious of hormones. It conjures up thoughts of muscles and masculinity. In fact, testosterone does fuel sex drive and muscle mass, but it also regulates mood and bone strength. When a man's level falls below normal, a doctor may prescribe shots, gels, or patches.  But there is some debate over who needs treatment.

A slow drop in testosterone is a normal part of aging, sometimes called "andropause" or "male menopause." For many men, this doesn't cause any significant problems or symptoms. Others may notice a decline in muscle mass, depression, or less interest in sex.

Low testosterone can cause visible changes in some men:

• Smaller, softer testicles
• Larger breasts
• Thinner muscles (happens slowly over a period of years)
• Loss of body hair (also happens slowly, usually over a period of years)

You may think osteoporosis, or brittle bone disease, is a woman's disease, but it can affect men as well. Low testosterone is a common cause. As testosterone levels fall, the bones may get thinner, weaker, and more likely to break.

A drop in testosterone doesn't always interfere with sex, but it can make it more difficult for your brain and body to get aroused. Some men may notice a drop in libido, while others may lose interest in sex completely. Low testosterone can also make it tougher to get or keep an erection.

Some men have subtle problems like mood changes, poor concentration, and less energy. These symptoms can easily be caused by other health problems though, like anemia, depression, sleep troubles, or a chronic illness.

Testosterone helps a man's body make sperm. When levels of the hormone are low, their sperm "count" can be low, too. Without enough sperm, they may not be able to father a child.

Getting older is the most common reason testosterone levels dip. Illnesses are sometimes to blame, including:

• Type 2 diabetes
• Liver 
• obesity
• Pituitary gland problems
• Testicle injuries
• Tumors

Radiation therapy, chemotherapy, and steroid medicines can also affect testosterone levels.

Your doctor may suggest a testosterone test if you have:

• Erectile dysfunction
• Lower sex drive
• Low sperm count
• A loss of height, body hair, or muscle size

If you have an illness known to lower testosterone, your doctor may want to test your levels of the hormone.

Testosterone is usually measured with a blood test done early in the morning, when levels are highest. Normal levels range from 300 to 1,000 ng/DL. Your doctor may want to run this test a second time before diagnosing low testosterone.

If you have low blood levels of testosterone AND symptoms that affect your daily life, your doctor may suggest taking supplemental testosterone.  Not everyone with low testosterone will need treatment. You may want to see a specialist to discuss the risks and possible benefits of treatment. Look for a urologist or an endocrinologist, a doctor who treats hormone problems.

If you need treatment, your doctor may prescribe testosterone to boost your levels. Some studies suggest this can strengthen men's muscles, protect their bones, and improve their sex drive, improve erectile dysfunction, and contribute to improved mood. But the effects can be quite different from one man to the next.

Testosterone comes in several forms, including shots, gels, patches, and tablets you place on your gums. Injections are the least expensive option, but they can be painful. You take the shots every 2 to 4 weeks, as prescribed by your doctor. You may also be able to get the medicine without injections by using a nasal pump. Your  testosterone levels can swing up and down between doses.

These are placed directly on your skin. The hormone seeps through the skin, and is slowly released into the blood. Because gels and patches are applied every day, they keep a steady level of testosterone. However, they can cause itching, irritation, and blisters at the spot where they're applied. Women and children should not touch skin treated with a gel or patch.

Tablets are placed on the gums above your incisors every 12 hours. As the gel-like tablet dissolves it slowly releases testosterone. Gum tablets can cause a bitter taste, irritated mouth, tender gums, or headaches. These side effects may get better with time. You can eat, drink, and kiss women and children while using testosterone tablets. Testosterone pellets are placed under the skin with low continual release of T for 3-6 months which eliminates the need for a weekly or daily testosterone application. 

Testosterone therapy has some drawbacks. Some men may develop:

• Too many red blood cells
• Sleep apnea
• An enlarged prostate
• Acne

The risks and benefits of taking testosterone for many years are not known, because large studies haven't been completed, yet. Some researchers suggest there might be a higher risk of heart disease. But the evidence is still not conclusive.

There's some concern that long-term use of testosterone may cause prostate cancer in older men. Men taking testosterone will need regular checkups to look for early signs of prostate cancer. This covers: All men over 50, men over 40 with a family history of prostate cancer, and all African American men.

Men with these conditions shouldn't take testosterone:

• Prostate or breast cancer
• Poorly controlled heart disease
• Untreated sleep apnea
• Too many red blood cells
• Clotting disorders