ABSTRACT
Mammary glands and reproductive tracts are controlled by similar hormones and, therefore, the exposure to hormones and synthetic analogs shows profound effects on mammary glands in experimental animals, while it is far from conclusive in humans. The long-term effects of perinatal treatments with hormones on normal mammary gland growth vary according to the doses, types, and treatment periods of hormones and the ages, sexes, and strains of animals. Neonatal treatment with estrogen, progesterone, or androgen induced an increase in mammary tumor development in several strains of mice bearing mammary tumor virus (MTV), which is an essential factor for neoplastic mammary response to perinatal hormone treatment as well as for spontaneous mammary tumor development in mice. There are some papers on the long-term effects of neonatal hormone treatments on carcinogen-induced mammary tumorigenesis in MTV unexpressed mice, all of which were negative. Cell responsiveness or susceptibility to hormones is another important factor for cell growth.
