Variation in spontaneous chromosomal damage as a function of biologic rhythms in women.

An unequivocal observation of a higher rate of cellular genetic damage in terms of increased frequencies of sister chromatid exchanges (SCEs) and chromosome aberrations during "ovulatory" and "estrogenic" stages as compared with those of "progestogenic" stage of the menstrual cycle in women and the reported fluctuations in SCEs as a function of time in men indicate that chronobiologic considerations are essential in the design of studies of humans and animals experiments. It seems that female subjects are more influenced by biologic rhythms because of specific hormonal cycles and are sensitive to genetic damage during ovulatory/estrogenic stages of the menstrual cycle.