Diurnal and seasonal rhythms of melatonin, cortisol and testosterone in interior Alaska

The diurnal variations in the secretory patterns of melatonin, cortisol and testosterone were studied in a Fairbanks, Alaska population who were unadapted to the extreme light variations of the North. Statistically significant variations in hormonal levels were found in both diurnal and seasonal rhythms. Prominent findings included unusually high levels of cortisol at 0200 and 0800 in the fall and elevated daytime levels (1030) of melatonin in the winter. These results indicate a delayed phase secretory pattern when compared to the normal pattern at lower latitudes. These findings imply possible underlying physiological causes for the high incidence of behavior disorders such as depression and alcoholism in Alaska and circumpolar environments in general.