Hormonal factors in human carcinogenesis

Summary A synopsis is presented of hormone-cancer relationships as seen by an epidemiologist. Emphasis has been placed on reproductive risk factors and cancers of the endometrium, ovary and breast. Although there are definite parallelisms in this regard the aetiological mechanisms for these three sites may be different.Evidence is accumulating that the protective effect of an early first birth and of subesequent pregnancies on breast cancer risk can be understood biologically in terms of interference with the occurrence of preneoplastic lesions.The Journal of Cancer Research and Clinical Oncology publishes in loose succession Editorials and Guest Editorials on current and/or controversial problems in experimental and clinical oncology. These contributions represent exclusively the personal opinion of the author.Presented at the EACR mecting, Copenhagen, 21 September 1983