Testosterone is the principal male sex hormone. The testicles are the primary site of testosterone production. Throughout life, testosterone has in important role in male development and health, which begins before birth and extends through senescence. The skin, musculoskeletal system, genitourinary system, cardiovascular system and nervous system are all directly influenced by testosterone. Deficiencies and excesses of this vital hormone can cause significant health concerns.
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Sexual Development in the Womb
The first important role of testosterone in the life of a male occurs just weeks after conception. At approximately the seventh to eighth week after conception, the male testicles become recognizable and begin producing testosterone. Under the influence of the testosterone produced by the developing baby, the male external genitals form. Failure of the testes to produce testosterone during this critical phase of fetal development leads to the formation of female genitals. Another disorder, androgen insensitivity syndrome, prevents the developing male from responding to the presence of testosterone. Due to the lack of response to testosterone, these infants are genetically male but are born with female genitals, explains Bruce Gottlieb, Ph.D., and colleagues in “Gene Reviews.”
Pubertal Development and Growth
Shortly after birth, the testicles stop producing any appreciable amount of testosterone. As a boy approaches puberty, hormones from the pituitary gland and hypothalamus in the brain signal the testicles to resume production of testosterone. The testes grow and the production of testosterone increases in kind. Ohio State University Medical Center explains that under the influence of testosterone, all of the changes of male puberty occur, including growth of genital, facial and body hair; growth of the scrotum and penis; beginning of sperm production; deepening of the voice; loss of body fat and accumulation of muscle mass; increasing bone mass; and the final growth spurt to achieve adult height.
Maintenance of Adult Vitality
Continued testosterone production throughout adult life proves an important contributor to overall health among men. Testosterone deficiency can cause a variety of physical, metabolic and mental disturbances. The Endocrine Society reports that testosterone deficiency may cause increased risk for coronary heart disease and diabetes mellitus, decreased cognitive function, and increased body fat. Other possible effects of an abnormally low testosterone level include decreased bone density, decreased sexual interest, impotence, impaired fertility, testicular shrinkage, loss of body hair and muscle mass, hot flashes, irritability and depression. Although the production of testosterone by the testes decreases gradually throughout adult life, testosterone levels that drop to the point of causing significant adverse effects are abnormal. Testosterone replacement therapy can alleviate the symptoms of a low testosterone in older males, a condition sometimes referred to as “andropause.”