Major female sex hormone, involved in the control and regulation of the menstrual cycle.
Like all steroids hormones, the estrogens derive from cholesterol. The three major natural forms of estrogen in women are; estrone (E1), estriol (E3), and estradiol (E2, with the latter being the strongest of the family). Another type of estrogen called esteretrol (E4) is produced only during pregnancy. Estradiol is the predominant estrogen during the reproductive years both in terms of serum levels as well as in terms of estrogenic activity. The main functions of estrogens are the control and regulation of the menstrual cycle, thickening of the uterus lining, triggering the Luteinizing Hormone surge and stopping the menses. They also promote the development of female secondary sexual characteristics, such as breast development. During menopause, the predominant circulating estrogen is estrone, while during pregnancy it is estriol. In males, estrogens regulate certain functions of the reproductive system, important to the maturation of sperm and libido regulation. Estrogens also have many other essential roles such as regulation of lipidic metabolism, bones metabolism, regulation of coagulation process, sexual behavior and more.