[Diurnal variation of glucose tolerance and insulin secretion in man (author's transl)]

The present investigation was designed to determine whether the circadian rhythm of glucose utilization is based on a quantitatively different release of insulin and/or on changing secretory dynamics of the hormone. 22 healthy men received three oral glucose tolerance tests in the morning, afternoon and evening of the same day. The blood sugar levels in the afternoon and evening tests were significantly higher than those found in the morning tests. Also the plasma insulin response was higher in the afternoon than in the evening, but it showed a delayed rise and late peak response. In the evening the normal subjects responded as mild diabetics.