østradiol

østradiol, also known as estradiol (E2), is a steroid hormone and the most potent natural estrogen in humans. It is produced primarily by the ovaries in premenopausal individuals, with additional contributions from the placenta during pregnancy and from adipose tissue in both sexes. As a ligand for estrogen receptors ERα and ERβ, østradiol regulates gene expression and non-genomic signaling in a wide range of tissues.

Chemically, østradiol is a phenolic steroid derived from cholesterol. Its production requires the enzyme aromatase to convert androgens to estrogens, a step governed by the hypothalamic-pituitary-gonadal axis, with luteinizing hormone and follicle-stimulating hormone playing key regulatory roles.

Physiological roles of østradiol include the development and maintenance of female reproductive tract and secondary sexual characteristics, regulation of the menstrual cycle and ovulation, maintenance of bone density, and influences on cardiovascular, metabolic, and neural function. In both sexes, estrogenic signaling contributes to mucosal health, lipid profiles, and mood regulation.

Medical uses of østradiol include hormone replacement therapy for menopausal symptoms and osteoporosis prevention, as part of combined oral contraception, and in gender-affirming hormone therapy. It is also used in certain hypogonadal conditions to restore and maintain endogenous estrogen effects.

Pharmacokinetics and administration vary by formulation. Oral forms undergo first-pass metabolism, while transdermal, vaginal, and injectable forms provide alternative routes. Common preparations include estradiol valerate and estradiol cypionate. Metabolism occurs in the liver to estrone and estriol, with conjugation and renal and biliary excretion. Side effects may include thromboembolic risk, nausea, breast tenderness, and headaches; contraindications include active thromboembolism, liver disease, pregnancy, and estrogen-sensitive cancers.