Estrogeenin

Estrogenin, in Finnish usage referring to the estrogens, are a group of steroid hormones that regulate development and function of the female reproductive system and secondary sexual characteristics. The principal estrogens in humans are estradiol (E2), estrone (E1), and estriol (E3). Estradiol is the most potent and predominant during reproductive years; estrone is more prominent after menopause, and estriol is largely produced during pregnancy.

Estrogens are synthesized from cholesterol. In the ovaries, theca and granulosa cells convert androgens to estrogens via the aromatase enzyme. Peripheral tissues such as adipose tissue can also produce estrogens, particularly after menopause. Estrogen levels rise and fall in coordination with the menstrual cycle and are influenced by the hypothalamic-pituitary-gonadal axis.

Functions of estrogens include the development and maintenance of the female reproductive tract, regulation of the menstrual cycle and ovulation, and promotion of secondary sexual characteristics. They also contribute to bone health, cardiovascular function, cognitive and mood processes, and skin and vaginal tissue integrity. Regulation occurs through feedback interactions with the hypothalamus and pituitary, modulating the release of GnRH, FSH, and LH.

Clinical aspects cover estrogen deficiency and excess. Hormone replacement therapy and combined hormonal contraceptives use estrogens to treat symptoms or prevent pregnancy, with risks such as venous thromboembolism, certain cancers, and cardiovascular effects. In men, estrogens arise from aromatization and play roles in bone density and reproductive function. Measurement often centers on serum estradiol, which varies across life stages.