The pattern of hormonal circadian time structure (acrophase) as an assessor of breast-cancer risk.

Through many hormones are secreted in a pulsatile manner, their secretion pattern can be superimposed by a 24-hour sinusoidal curve. The sinusoidal curve is then characterized by the estimated peak clock time location (acrophase), the adjusted mean (mesor) and the amplitude. When the distribution of the acrophases of 12 hormones was compared among women with regard to their age and to the level of risk of developing breast cancer, statistically significant differences were revealed between distribution patterns of acrophases of women with high (n = 12 and 45 circadian profiles) or low (n = 12 and 41 circadian profiles) risk of developing breast cancer. However, when the amplitude/mesor ratios of the corresponding hormonal rhythms were analyzed, significant differences occurred between age groups rather than between risk levels. These observations suggest that the endocrine time structure between individual women can be used as an assessor of breast-cancer risk.