Urinary excretion of IGF-I and growth hormone in children with IDDM

OBJECTIVE - To compare the urinary output of insulinlike growth factor I (IGF-I) and growth hormone (GH) in prepubertal and pubertal children with insulin-dependent diabetes mellitus (IDDM) versus nondiabetic subjects and to analyze the relationship between the urinary excretion of these peptides and degree of metabolic control. RESEARCH DESIGN AND METHODS - Group 1 included 30 IDDM patients who had had diabetes for 4.9 ± 0.7 yr and had normal renal function (mean age 11.6 ± 0.9 yr); group 2 consisted of 31 control subjects (mean age 9.2 ± 0.6 yr). Sensitive radioimmunoassays were used to measure IGF-I and GH in urine aliquots from 12-h timed overnight collections that had been dialyzed, concentrated 50-fold, and lyophilized. RESULTS - Significantly lower IGF-I and GH outputs per kilogram body weight per 12 h were observed in IDDM subjects compared with control subjects. When data were expressed per kilogram of body weight, no difference was observed between the urinary output of IGF-I and GH between prepubertal and pubertal subjects within group 1 or group 2. The prepubertal children had significantly lower HbA₁ than the pubertal population; however, no correlation was found between urinary output of IGF-I or GH and HbA₁. A positive correlation was observed between urinary IGF-I and GH (r = 0.85, P < .001). CONCLUSIONS - Patients with long-standing IDDM excrete significantly lower urinary levels of IGF-I and GH compared with normal subjects. Serial measurements of these peptides from onset of IDDM are needed to define whether the changes observed are present at diagnosis or are secondary to duration of disease.