[Effect of estrogens and antiestrogens on the endometrium]

Estrogens act through specific receptors located in the nuclei of epithelial and stromal cells of the endometrium. Estrogens stimulate the synthesis of these receptors and the progesterone inhibits their synthesis. Estrogens induce the proliferation of the mucosa during the proliferative phase. They also stimulate the synthesis of receptors for the progesterone, which is a prerequisite for progesterone activity. Hyperplasias most of the time do not contain cytological atypia and are developed under a hyperestrogenic background. They contain receptors for estrogen and progesterone, and are able to respond to progestogens. Hyperplasias with cytological atypia are precancerous lesions, associated with an hyperestrogenic or atrophic background. In the later case, they may be focal and are better diagnosed by hysteroscopy. They are best managed by simple hysterectomy. Progesterone may be used if the patient desires to conceive. Endometrial cancers are either associated with an hyperestrogenic or atrophic background. In the later case, they are often of serous or clear cell type. Endometrial effects of antiestrogens are known only for tamoxifene. Tamoxifene has an atrophic effect but sometimes may induce an estrogenic stimulation of the endometrial mucosa through the alpha and beta estrogenic receptors. Polyp is the most frequent abnormality diagnosed but endometrial cancer is significantly more frequently diagnosed than in a control population. It is well differentiated and does not modify the survival of the patient.