A potential relation was evaluated between nocturnal urinary growth hormone (GH) excretion as a parameter for integrated GH secretion and the course of blood glucose (BG) levels during night and morning hours. Twelve diabetic children aged 11.6 +/- 2.0 years (mean +/- SD), with diabetes duration 4.4 +/- 1.6 years, took part in the study. Urine for GH estimation by a highly sensitive EIA was collected from 24.00 to 07.00 h during a diabetic summer camp. BG was monitored at 24.00, 04.00 and 07.00 h. Mean nocturnal GH excretion measured from 158 collections was 5.6 +/- 5.1 ng/g creatinine, with a wide range of 0.36-36.6. Remarkable intra-individual variations were found between distinct nights. GH excretion correlated positively with BG levels at 07.00 h (p = 0.003) and with the increment of BG between 24.00 and 07.00 h (p = 0.002). Thus, endogenous variations in nocturnal GH levels may be involved in the day-to-day fluctuations in fasting BG in diabetic subjects.