Sexual Development

What effects do estrogens and testosterone have on females and males?

At first, male and female human embryos are nearly identical in appearance. Then, during the seventh week of development, the reproductive systems of male and female embryos begin to develop along different lines. The male pattern of development is triggered by the production of testosterone in the gonads of the embryo. In female embryos, testosterone is absent and the female reproductive system develops under the influence of estrogens produced in the embryo's gonads.

Estrogens and testosterone, which have powerful effects on the body, are steroid hormones primarily produced in the gonads. In addition to shaping the sexual development of the embryo, these hormones act on cells and tissues to produce many of the physical characteristics associated with males and females. In females, the effects of the sex hormones include breast development and a widening of the hips. In males, they result in the growth of facial hair, increased muscular development, and deepening of the voice.

In childhood, the gonads and the adrenal cortex produce low levels of sex hormones that influence development. However, neither the testes nor the ovaries can produce active reproductive cells until puberty. Puberty is a period of rapid growth and sexual maturation during which the reproductive system becomes fully functional. The age at which puberty begins varies considerably among individuals. It usually occurs between the ages of 9 and 15, and, on average, begins about one year earlier in females than in males. Puberty actually begins in the brain, when the hypothalamus signals the pituitary to produce two hormones that affect the gonads—follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

In Your Notebook Summarize the effects of estrogens on females and testosterone on males.