[Shift and night work--is it a cancer risk factor?].

This paper presents the results of studies on the effects of circadian rhythm disturbances and melatonin on the carcinogenic process. It is thought that melatonin synthesis mostly influences the generation of breast and colorectal cancers. However, its influence on the development of prostate, ovarian, and endometriosis cancers is also suggested. It should be remembered that many other important risk factors contribute to the pathogenesis of these diseases. It is essential for occupational medicine physicians to pay special attention to so called "oncological risk" in workers with long duration of employment in the shift-work system as this group of workers is also exposed to other cancer risk factors. Exogenous melatonin supplementation along with reduced effect of shift work is very important from the practical point of view.