ABSTRACT
Female sex steroid hormones are: estradiol, estrone, estriol and progesterone. This chapter deals with the concept of A ring aromatisation in the biosynthesis of estrogens, and presents the list the principal physiological actions of estradiol. It discusses briefly the known and suspected impact of estrogens on diseases, notably breast cancer and cardiovascular disease. The chapter examines the physiological actions of progesterone, and have knowledge of some important therapeutic uses of synthetic progestogens. Estrogen's actions are manifested through their cessation at menopause. The actions of estradiol on the cell are mediated by specific estrogen receptors. There are two main subtypes encoded by different genes: ER-alpha and ER-beta. Both subtypes express the actions of estradiol through: genomic mechanisms and non-genomic actions. Estrogen deficiency is associated with increased bone resorption and there is much evidence that hormone replacement therapy reduces the incidence of fractures in postmenopausal women.
