Testosterone is a basic fundamental, hormone found in all mammals. It is the principal androgen, or male sex hormone, although it appears in both genders.

No, Testosterone is found in both men and women.
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).

Menopause itself does not seem to play a role in a reduction of testosterone levels in women. With advancing age, in both men and women, the body produces decreasing amounts of testosterone over time.

Testosterone is the most important hormone in men.

While it helps to maintain sex drive, sperm production, and body hair, testosterone is also responsible for maintaining muscles and bones. When testosterone production is low in men, sexual dysfunction is a common complaint; but other nonspecific symptoms such as depression, mood changes, weight gain, or fatigue, have been reported.

Low levels of testosterone in men can affect a man in the following ways:
- Loss of sexual interest and function
- Erection problems
- Increased breast size
- Hot flashes
- Problems with memory and concentration
- Mood problems such as irritability and depression
- Smaller and softer testicles
- Loss of muscle strength and weakened bones

Symptoms of low testosterone levels in women include:
- Hot flashes
- Irritability
- Loss of sexual desire
- Sleep disturbances
- Loss of muscle mass
- Decreased bone density (osteoporosis)

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. These hormones travel through the bloodstream to activate the sex organs in both men and women.

Diabetes. Men with diabetes are more likely to have low testosterone. Moreover, men with low testosterone are more likely to develop diabetes later. Testosterone helps the body's tissues take up more blood sugar in response to insulin. Men with low testosterone more often have insulin resistance.

Note: Scientists aren't sure whether diabetes causes low testosterone, or the other way around. Still, a link between diabetes and low testosterone is well established.

Yes. Many people with low testosterone have no symptoms. Only a blood test can determine a person's testosterone levels. The Endocrine Society considers 300 to 1,200 nanograms per deciliter (ng/dL) normal, and that less than 300 is low. Doctors usually use a blood test and a number of symptoms to make a diagnosis and to determine whether treatment is needed.

No. From puberty, when a boy starts to grow a beard and pubic hair, testosterone affects hair growth in men. But it doesn't affect growth on all parts of the body the same way. Low testosterone can cause you to lose body or facial hair, but it doesn't cause male pattern baldness. Genetics have more to do with male pattern baldness.