Abstract
In 13 subjects with type 1 (insulin dependent) diabetes mellitus the 24 hour insulin
requirements to maintain euglycemia were assessed by means of feed back controlled
insulin infusion. For the study steady state conditions, i.e. bed rest and fasting
were required. Venous blood samples were collected, at 2 hour intervals, for the measurement
of glucagon, growth hormone and cortisol. During the day, the insulin demand showed
small changes. However, the early morning requirement for insulin was twice as much
as the daytime demand (dawn phenomenon). There was a significant difference (p < 0.05)
in the insulin requirement between 6.00 to 8.00 hours in the morning and 12.00 to
16.00 hours in the afternoon. The plasma glucagon levels showed no significant changes
during the euglycemic period (median range from 28.7 to 30.1 ng/ml) (p < 0.05). The
median of the growth hormone level decreased throughout the night from a peak of 4.41
ng/ml at midnight to a nadir of 1.05 ng/ml at 4.00 hours. There was a significant
difference (p < 0.05) between the growth hormone concentration between midnight and
the early morning. The cortisol concentration indicated a circadian variation. The
median was significantly higher from 4.00 to 8.00 hours in comparison with the median
at 20.00 to 24.00 hours (p < 0.05). The results of the study showed that the early
morning rise in the insulin demand is related to the increased early morning cortisol
secretion and to the nocturnal peaks of growth hormone concentration (p < 0.05).
Key words
Insulin Dependent Diabetes Mellitus - Circadian Rhythms - Euglycemia - Glucagon -
Growth Hormone - Cortisol - Diurnal Patterns - Insulin Requirement - Blood Glucose
