oestrogen

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Any of a group of hormones produced by the ovaries of vertebrates; the term is also used for various synthetic hormones that mimic their effects. The principal oestrogen in mammals is oestradiol. Oestrogens control female sexual development, promote the growth of female secondary sexual characteristics at puberty, stimulate egg (ovum) production, and, in mammals, prepare the lining of the uterus for pregnancy. In other words, together with another hormone, progesterone, they regulate the growth and functioning of sex organs for sexual reproduction. Oestrogens are also used in female oral contraceptives, to inhibit the production of ova.

Oestrogens are used therapeutically for some hormone disorders and to inhibit lactation. US researchers in 1995 observed that oestrogen plays a role in the healing of damaged blood vessels. It has also been found that women recover more quickly from strokes if given a low oestrogen dose.

Modelled on the French tricolour, the vertical stripes represent liberty and revolution. The almost square proportions of the flag are unusual. Effective date: 23 January 1831. >>