Testosterone is an important hormone with regard to physical development of males, reproductive function in males, and sex drive in both males and females. While low testosterone is rare in young adult males with undamaged testes, it's not uncommon for testosterone levels to fall off as both men and women age. Further, damage to the testes can result in low testosterone, since the gonads are responsible for production of the hormone. There are several effects of low testosterone.
Hypogonadism
One of the most obvious physical effects of low testosterone is hypogonadism, or small testes, explains MayoClinic.com. Depending upon whether a male has low testosterone levels from birth or whether the low testosterone arises later in life as the result of injury to the testes, hypogonadism may be present throughout a man's life or may develop. Very low testosterone in male embyros can even result in development of female external genitals--while the cells contain male chromosomes, the lack of testosterone production leads the body to develop female external sex organs rather than male. Alternately, testes are present but may be small and minimally functional or non-functional.
Low Sex Drive
In both men and women, testosterone is responsible for the sex drive, or the desire to engage in sexual activity. Normal, younger adult males produce constant quantities of testosterone, explains Dr. Lauralee Sherwood in her book "Human Physiology." The testosterone hormone is produced by the Leydig cells of the testes in men, which are stimulated to produce the hormone through the action of LH, or luteinizing hormone, from the anterior pituitary. In women, thecal cells of the ovaries produce testosterone, though as with female sex hormones, amounts can vary through the month. As men and women age, testosterone production falls off, leading to reduced sex drive in both genders.
Reproductive Effects
Men can experience difficulty with physical logistics of reproduction in addition to a decrease in sex drive in response to low testosterone. Notes Dr. Gary Thibodeau in his book "Anatomy and Physiology," testosterone levels allow for development and maintenance of erections as well as sperm development. As such, effects of low testosterone in men can include erectile dysfunction as well as low or absent sperm count. Typically, men with infertility are tested for normal levels of testosterone, due to the impact of the hormone upon normal reproductive function.
References
- MayoClinic.com: Hypogonadism
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
