Estrogens plays an essential role in the etiology of human breast, ovarian and endometrial carcinoma. Activation of estrogen receptors contributes to the growth and metastasis of these common estrogen-dependent tumors found in women. Recent studies reveal that melatonin, main hormone secreted by pineal gland, has been involved in the regulation of cancer cells growth. The oncostatic properties of this molecule has been considered on different kinds of tumors but especially on hormone dependent breast cancer.

The presence of estrogens in the male gonad is now well documented, however the role of the hormones in regulation of function of male reproductive system is not fully understood. The using of molecular biology methods provided evidence that the cells of male reproductive system organs are able to produce estrogens via aromatization of androgens and are estrogen target. The cytochrome P450 aromatase and both isoform of estrogen receptors are expressed not only in Leydig and Sertoli cells, but also in germ cells, spermatozoa, the cells of epithelium in the efferent ductules and epididymis.

Phytoestrogens are plant-derived chemical compounds which may affect reproductive processes in humans and animals. In their target cells, phytoestrogens may mimic (estrogenic effects) or antagonize (antiestrogenic effects) action of endogenous estrogens. In the current paper, contemporary views are presented on intracellular mechanism of phytoestrogen action in ovarian, uterine, and mammary gland cells.