Insulin-Like Growth Factor-1 at Diagnosis and During Subsequent Years in Adolescents with Type 1 Diabetes

Background. Type 1 diabetes (T1D) in adolescents is associated with alterations in the insulin-like factor system probably caused both by a deranged metabolism and insulinopenia in the portal vein. Objective. To study how the circulating IGF-1 is affected at diagnosis and during subsequent years in adolescents with T1D. Methods. Ten girls and ten boys with type 1 diabetes (T1D), aged 13.0 ± 1.4 (mean ± SD) years at diagnosis, took part in the study. Blood samples were drawn at diagnosis and after 3, 9, 18, and 48 months. HbA1c, total IGF-1, and C-peptide were measured. Results. At diagnosis, the patients had high HbA1c, low IGF-1, and measurable C-peptide. After the start of insulin treatment, maximal improvement in glycemic control and IGF-1 occurred within 3 months and then both tended to deteriorate, that is, HbA1c to increase and IGF-1 to decrease. C-peptide decreased with time, and after 4 years, half of the patients were C-peptide negative. At diagnosis, C-peptide correlated positively to IGF-1 (r=0.50; p<0.03). C-peptide correlated negatively with insulin dose (U/kg) after 18 and 48 months from diagnosis (r=−0.48; p<0.03 and r=−0.72; p<0.001, resp.). Conclusions. In conclusion, our results show that in newly diagnosed adolescents with type 1 diabetes and deranged metabolism, the IGF-1 level is low and rapidly improves with insulin treatment but later tends to decrease concomitantly with declining endogenous insulin secretion.