Why are ESTROGENS so important for WOMEN?

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Oestrogens are a group of sex hormones synthesised in numerous tissues. In women of childbearing age they are produced mainly by the granulosa cells of the ovary from cholesterol, in pregnant women the main site of oestrogen production is the placental syncytiotrophoblast, in post-menopausal women they are produced mainly by the stromal cells of adipose tissue. Additional sites of oestrogen production are numerous areas of the brain and genital skin regions. The oestrogens produced in the various tissues are specific and it is therefore possible to distinguish four different types of oestrogens: theoestradiol (E2), l'estrone (E1), l'estriol (E3)and theestetrole (E4).  The 17β-estradiol (E2) is the most represented oestrogen during a woman's childbearing years and its synthesis occurs mainly in the granulosa and theca cells of the ovarian follicle¹. High concentrations are found during pregnancy estriol (E3), a product of placental synthesis from dehydroepiandrosterone sulphate (DHEAS)². In menopause, on the other hand, theestrone(E1)which derives largely from the transformation of androstenedione in adipose tissue by the action of the enzyme aromatase³. L'estetrole (E4) it is only synthesised during pregnancy in the placenta and foetal liver and has in recent years attracted clinical interest as it has similar functions to oestradiol on all cells and tissues with the exception of the breast, on which it acts anti-oestrogenically⁴. In women, oestrogens possess different biological activities. In post-natal life they act mainly during puberty, bringing about the changes that lead to the completion of sexual differentiation, the development of secondary sexual characteristics, and the stroma of the mammary gland. From puberty to menopause they act mainly on reproductive function by promoting endometrial proliferation in order to prepare a favourable environment for embryo implantation in the event of conception. Outside the strictly reproductive sphere, the biological action of oestrogen manifests itself at the level of extra-genital structures such as the mucous membranes, skin, hair follicles, bone tissue and on certain metabolic processes. All mucous membranes are sensitive to the trophic action of oestrogen and this action is most evident at the level of the vagina, bladder, urethra, mouth and gums. At the skin level, they improve trophism, reduce sebaceous secretion and promote hair growth.  At puberty, they promote ossification of the conjugating cartilages of the long bones, bringing the growth phase of stature to an end. They also facilitate bone calcium fixation and help maintain bone mass.⁵. In the menopause, oestrogen deficiency promotes osteoporosis due to increased bone resorption by osteoclasts. Oestrogens promote lipogenesis by determining the particular arrangement of fat typical of the female sex. They have a preventive effect on cardiovascular disease as they reduce triglyceride levels and stimulate the increase in high-density lipoprotein (HDL), preventing the formation of atheromatous plaques. This helps to explain the lower incidence of cardiovascular disease in women compared to men during the reproductive period.⁶. They also have the function of regulating many brain activities, including memory and attention.⁷. 

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