The hormones critical to sexual reproduction and development are often referred to as sex hormones. These hormones influence the physical expression of male or female characteristics, including the development of the breasts in females and increased body hair in males. They also help control reproductive processes, such as ovulation and the production of sperm. The human body produces these hormones naturally, but doctors also prescribe synthetic and natural forms of these hormones in medical treatments. For example, doctors often prescribe hormones such as estrogen and progesterone for birth control or the treatment of menopause symptoms.
Sex hormones have a significant effect on human reproduction and the development of characteristics specific to each sex. For example, when a woman begins to develop breasts, this is the result of this hormone influence. The same goes for when a male's voice deepens and he notices more hair growth on his face.
Estrogen, progesterone, and testosterone are among the most well-known and commonly discussed hormones that affect reproduction and development. Estrogen and progesterone are most frequently associated with females, while testosterone is usually discussed as it applies to men. These primary hormones are present in both male and females, however. Estrogen and progesterone are simply found in higher levels in the female body while testosterone is the dominant one in males.
While the work of sex hormones becomes most evident once a person reaches puberty, they actually are present at birth. The levels of these hormones in a person's body do change at various stages of life, however. For example, the levels of many types of hormones increase during puberty and stay elevated during the reproductive years. Around middle age, many people start to experience a decline in levels of some hormones, many of which will progressively decrease with continued aging.
The endocrine glands have most of the responsibility for producing and releasing sex hormones into the body. In females, these glands are referred to as the ovaries, and they not only produce hormones, but also eggs for release during ovulation. In males, the endocrine glands are referred to as the "testes," and have the responsibility for the production of hormones and sperm. When a person's endocrine glands fail to function as they should or fail to produce the right levels of hormones, the result can be infertility or sub-fertility, recurrent pregnancy loss, sexual dysfunction, and a range of unpleasant physical symptoms.
