Testosterone is a hormone with a powerful effect on a number of body organs, including your vascular system, muscles, brain, and bones. It's best known as a sex hormone that plays a major role in physical development, determining whether you develop male or female features prenatally and whether you develop male characteristics at puberty. Testosterone also affects sexual functioning.
Where It Comes From
While testosterone is widely known as the "male hormone," it's actually produced by both males and females. Men release a large amount of testosterone from their testicles, while women produce a smaller amount in their ovaries. Both sexes produce a small amount in the adrenal glands. The pituitary gland controls testosterone levels in both sexes by releasing a hormone known as luteinizing hormone, or LH.
Normal Range
Testosterone levels are relatively low during childhood and increase at the onset of puberty. They peak during the teen and early adult years, gradually dropping about 1 percent a year after age 30, according to MayoClinic.com. The University of Michigan Health System publishes a table showing that a male infant typically has less than 30 nanograms/deciliter of testosterone in his blood while a female infant has less than 10 ng/dL. By age 15, boys should be in the range of 100 to 540 ng/dL; girls, 8 to 53 ng/dL. Men in their 20s and 30s can expect a testosterone level from 270 to 1,080 ng/dL, compared to 10 to 70 ng/dL in women. After the age of 60 years, men can expect to have 350 to 720 ng/dL, while post-menopausal women should be between 7 and 40 ng/dL.
Effects
The effect of testosterone is most evident during puberty, when the significant rise in testosterone triggers larger muscle mass, facial and body hair, deeper voices and sperm production in adolescent boys. In women, testosterone levels affect menstrual cycles and fertility.
High Testosterone Levels
Women with high levels of testosterone can develop male characteristics such as facial and body hair, male-pattern baldness and a deeper voice. According to Lab Tests Online, elevated testosterone levels can also lead to irregular or absent menstrual cycles and female infertility. A high testosterone level in men might indicate cancer of the testicles or adrenal glands, according to the University of Michigan Health System.
Low Testosterone Levels
When testosterone levels drop too low, men may notice a lower sex drive, infertility, insomnia, increased body fat, reduced muscle, and even swollen or tender breasts. According to MayoClinic.com, low testosterone can also cause depression, sadness, decreased motivation and lower self-confidence.
Expert Insight
While there is a great deal of public interest in testosterone supplements to affect everything from a man's appearance to his sexual prowess, according to the National Institute of Aging, "Except for a relatively few younger and older men with extreme deficiencies, testosterone treatment is not deemed appropriate for most men at this time."
