Estrogen - Function

Function

The actions of estrogen are mediated by the Estrogen receptor (ER), a dimeric nuclear protein that binds to DNA and controls gene expression. Like other steroid hormones, estrogen enters passively into the cell where it binds to and activates the estrogen receptor. The estrogen:ER complex binds to specific DNA sequences called a Hormone response element to activate the transcription of some 137 ER-regulated genes, of which 89 are direct target genes. Since estrogen enters all cells, its action are dependent on the presence of the ER in the cell. The ER is expressed in specific tissues including the ovary, uterus and breast.

While estrogens are present in both men and women, they are usually present at significantly higher levels in women of reproductive age. They promote the development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. In males, estrogen regulates certain functions of the reproductive system important to the maturation of sperm and may be necessary for a healthy libido. Furthermore, there are several other structural changes induced by estrogen in addition to other functions.

• Structural
  • Promote formation of female secondary sex characteristics
  • Accelerate metabolism
  • Increase fat stores
  • Stimulate endometrial growth
  • Increase uterine growth
  • Increase vaginal lubrication
  • Thicken the vaginal wall
  • Maintenance of vessel and skin
  • Reduce bone resorption, increase bone formation
  • Reduce muscle mass
• Protein synthesis
  • Increase hepatic production of binding proteins
• Coagulation
  • Increase circulating level of factors 2, 7, 9, 10, plasminogen
  • Decrease antithrombin III
  • Increase platelet adhesiveness
• Lipid
  • Increase HDL, triglyceride
  • Decrease LDL, fat deposition
• Fluid balance
  • Salt (sodium) and water retention
  • Increase cortisol, SHBG
• Gastrointestinal tract
  • Reduce bowel motility
  • Increase cholesterol in bile
• Melanin
  • Increase pheomelanin, reduce eumelanin
• Cancer
  • Support hormone-sensitive breast cancers (see section below)
• Lung function
  • Promotes lung function by supporting alveoli (in rodents but probably in humans).
• Uterus lining
  • Estrogen together with progesterone promotes and maintains the uterus lining in preparation for implantation of fertilized egg and maintenance of uterus function during gestation period.
• Ovulation
  • Surge in estrogen level induces the release of luteinizing hormone, which then triggers ovulation by releasing the egg from the Graafian follicle in the ovary.
• Sexual receptivity in estrus
  • Promotes sexual receptivity, and induces lordosis behavior. In non-human mammals, it also induces estrus (in heat) prior to ovulation, which also induces lordosis behavior. Female non-human mammals are not sexually receptive without the estrogen surge, i.e., they have no mating desire when not in estrus.
• Lordosis behavior
  • Regulates the stereotypical sexual receptivity behavior; this lordosis behavior is estrogen-dependent, which is regulated by the ventromedial nucleus of the hypothalamus.
• Sexual desire
  • Sex drive is dependent on androgen levels only in the presence of estrogen, but without estrogen, free testosterone level actually decreases sexual desire (instead of increases sex drive), as demonstrated for those women who have hypoactive sexual desire disorder, and the sexual desire in these women can be restored by administration of estrogen (using oral contraceptive). In non-human mammals, mating desire is triggered by estrogen surge in estrus.