Oestrogene

Oestrogene, or estrogen in English, refers to a group of steroid hormones essential for the development and function of the female reproductive system. The principal natural estrogens in humans are estradiol (E2), estrone (E1), and estriol (E3). In some languages the term oestrogeen or œstrogène is used as well.

Biosynthesis and sources: In premenopausal women the ovaries are the main source of estrogens, regulated by the pituitary hormones. After menopause, peripheral tissues, especially adipose tissue, convert androgens into estrogens via the enzyme aromatase. The placenta also produces estrogens during pregnancy.

Mechanisms of action: Estrogens exert their effects mainly by binding to estrogen receptors, ER alpha (ESR1) and ER beta (ESR2). These receptors act as transcription factors to regulate gene expression (genomic effects) and can also trigger rapid, non-genomic signaling in various tissues.

Physiological roles: Estrogens govern the development of female secondary sexual characteristics, the maturation of the reproductive tract, and regulation of the menstrual cycle. They contribute to the maintenance of bone density, influence lipid metabolism and cardiovascular function, and affect brain, skin, and other tissues. In males, estrogens are present at lower levels but participate in spermatogenesis, bone health, and certain brain functions.

Clinical aspects: Estrogen deficiency can cause hot flashes, vaginal atrophy, and bone loss. Hormone replacement therapy (HRT) or combined estrogen–progestin therapy may alleviate menopausal symptoms and protect bone health, but they carry risks such as thromboembolism and certain cancers. Estrogens are also used in contraception and in some cancer therapies, often as synthetic derivatives (for example ethinylestradiol or conjugated estrogens).

Notes: The term oestrogene is used in some languages; in English the standard term is estrogen.