The hormone testosterone is an androgen, or male hormone. It's produced by the testes of the male and is responsible for many of the physical and emotional features that distinguish men from women. Male fetuses begin producing testosterone as early as 8 weeks gestational age, and this is responsible for the development of uniquely male body parts. Testosterone secretion increases during puberty, and production remains high throughout much of the remainder of a man's life.
Function
The major purpose of testosterone is the development and maintenance of male sexual characteristics, explains Dr. Lauralee Sherwood in her book "Human Physiology." Male gonads, the precursors to testes, begin producing testosterone while a fetus is still in utero. The hormone causes the development of male sex organs, including the glands that will produce semen, and the external male genitalia, including the penis and scrotum. In pubescent males, testosterone causes these organs to begin to function as they do in adults.
Features
A pubescent male develops many characteristics that are not found in younger boys or in women; these are due to the effects of testosterone. In his text "Anatomy and Physiology," Gary Thibodeau, Ph.D. notes that the larynx, or voice box, thickens, producing a deeper voice. Muscles become heavier and larger under the hormone's influence. The external genitalia enlarge and the internal reproductive organs begin producing sperm and semen. Additionally, body hair proliferates to a greater degree than seen in women.
Benefits and Drawbacks
Testosterone has some positive effects on male health, notes Dr. Thibodeau. Men, for instance, are less susceptible to osteoporosis than women, because testosterone causes bones to become more dense and harder than the bones of women. These sturdier bones are better able to support a man's larger, heavier frame, and allow the development of the typical male's heavy musculature. Unfortunately, however, testosterone also causes males to experience more severe acne than females and makes them more susceptible to abdominal fat, which is associated with heart disease in later life.
Expert Insight
Testosterone production is not limited to males, notes Dr. Sherwood. Women, who make the female hormones estrogen and progesterone, also produce a small amount of testosterone. While the quantity isn't sufficient to produce male sexual characteristics, it's nevertheless responsible for the female sex drive. Since women don't have testes, they must produce testosterone by converting female hormones into the androgen. As a result, menopausal women who don't make as much female hormone also develop a low testosterone level, consequently reducing their sex drive.
Mental Effects
In addition to its physical effects, testosterone also affects the brains of males. In their book "You: Having A Baby," Dr. Michael Roizen and Dr. Mehmet Oz note that testosterone produced by male fetuses destroys cells in the communication center of the brain and encourages brain cell growth in the sex and aggression centers. During puberty, increasing concentrations of testosterone foster even more aggression and sexual drive, producing some of the characteristic male psychological traits.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
- "You: Having A Baby"; Michael Roizen, M.D. and Mehmet Oz, M.D.; 2009
