Natural or synthetic substances that induce the changes in the UTERUS that precede OVULATION. They are also responsible for the development of the secondary sex characteristics in women: that is, the physical changes that take place in a girl at puberty, such as enlargement of the BREASTS, appearance of pubic and axillary hair, and the deposition of fat on the thighs and hips. They are used in the management of disturbances of the MENOPAUSE, and also in the treatment of cancer of the prostate (see PROSTATE GLAND, DISEASES OF) and certain cases of cancer of the breast.
The oestrogenic hormones of the ovary are OESTRADIOL and oestrone. The rapid degradation of natural oestrogens limits their use as therapeutic agents. Chemical substitution of the steroid molecule, as in ethinyl oestradiol, or the use of a non-steroidal synthetic oestrogen such as STILBOESTROL, greatly reduces the rate of degradation and enhances the therapeutic action. A further development has been the use of compounds which are not actually oestrogenic themselves, but which are slowly metabolised to oestrogenic substances, or substances such as chlorotrianisene, which are taken up in the body fat and then slowly released into the circulation. There is in fact little to choose between the various synthetic oestrogens. Ethinyl oestradiol is the most potent oral oestrogen, being 20 times more active than stilboestrol.
Other commonly used oestrogen drugs are dienoestrol and oestrol. The use of oestrogens in hormone replacement therapy (HRT) is dealt with in the entry on the MENOPAUSE.... oestrogens
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