[Is progesterone insufficiency carcihogenic?].

Estradiol is a natural estrogen which favors cellular hyperplasia at the level of its target organs. As for progesterone, its activity may be synergic or antagonist of estradiol. In the first case, progesterone has generally a secretory activity upon the target cells "prepared" by estrogens, in particular the cells of the female genital tract (uterus, breast). In the second case, progesterone may be an antiestrogen not only at the level of genital cells but also at the level of other receptors such as vascular system, etc. If an unbalance occurs in the quantitative and chronological ratio between estradiol and progesterone production (which determines the number of target cells and their secretory activity), a cellular dysplasia may be observed. This unbalance is generally characterized by an insufficiency in progesterone secretion which may be physiological (puberty, menopause) or pathological. Such a progesterone insufficiency may play a role in the pathogenesis of genital cancers (endometrial and possibly mammary). Experimental data which give some support to such an hypothesis are reported. They emphasize the importance of treatment of the progesterone insufficiency of the premenopausal period in women with the aim of preventing cellular dysplasia of the female genital tract.