A seasonal change in the diurnal rhythm of the excretion of a 3-methoxy-4-hydroxymandelic acid in man

In two series of experiments, one in the autumn and one in the winter on an Antarctic base, diurnal rhythms have been demonstrated in the urinary excretion of V.M.A. These persisted in spite of changes in the hours of daylight. There was a small rise in the total amount of V.M.A. excreted in winter, and an increase in the amplitude of the diurnal rhythm which was significant for one 4‐hr period of the day. However, in general, the diurnal rhythms were very similar. The most likely causes of the rise ‐ environmental temperature change, mood changes and alterations in posture ‐ do not appear to have been responsible. Possible long‐term changes, such as an increased response of the sympathoadrenal system to similar amounts of cold, i.e. cold acclimatization, cannot be dismissed.