Sexual maturation, estrogens

Reproductive organs are the primary source of the steroid hormones that influence sexual and reproductive functions. In men, the testes produce testosterone and similar androgens that are responsible for spermatogenesis and the secondary sexual characteristics of adult males.7,26 In women, sexual maturation and reproductive function are governed by the production of estrogens and progestins from the ovaries.27 The release of male and female sex steroids is controlled by hormones from the hypothalamus and anterior pituitary.32 The control of male and female hormone activity and the pharmacologic implications of these hormones are discussed in Chapter 30. 

Estrogen and progesterone play a primary role in promoting sexual differentiation in the developing female fetus. These hormones also become important in completing female sexual maturation during puberty. At... 

Estrogen—hormone present in both males and females. It is present in much larger quantities in females, however, and is responsible for many of those physical characteristics which appear during female sexual maturation. 

The hormonal events associated with ovulation are incompletely understood. Simplistically, a feedback loop is established between the hypothalamus-pituitary and the ovary at the onset of sexual maturity. Pituitary gonadotropins function to stimulate primitive follicles to secrete estrogen, progesterone, and... 

Estrogenic agents, listed in Table 5, hasten sexual maturation in the female. The widest use of estrogens is in the treatment of the menopause. Estrogens are also used in the control of cancer of the prostate in the male. 

Zearalenone possesses properties typical of estrogens such as estradiol. Feminization has been seen in young boars that are not sexually mature. Older, sexually mature boars are not affected by high levels of zearalenone, presumably because of their high endogenous testosterone production. 

Progesterone produces direct membrane effects [16]. These include actions that promote maturation of spermatozoa as well as oocytes and facilitation of the release of neurotransmitters such as dopamine and LH-releasing hormone (LHRH) (Fig. 52-7). Membrane actions of progesterone also activate oxytocin receptors in the hypothalamus in a way that enables oxytocin to turn on sexual behavior in the estrogen-primed female rat [3],... 

Estradiol is the major secretory product of ovary. Estrogens are required for normal maturation of the female. They stimulate the development of secondary sexual characters e.g. stimulate stromal development, ductal growth in the breast, growth of axillary and pubic hair and alter the distribution of body fat to produce typical female body contours. 

It is important to have the right equilibrium between testosterone and estrogens in males and females. Estrogens promote the development of female secondary sexual characteristics, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. In males, estrogens regulate functions of the reproductive system important to the maturation of sperm and may be necessary for a healthy libido. 

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