Effect of Diabetes and its Control on Insulin-like Growth Factors in the Young Subject with Type I Diabetes

Abstract

The influence of diabetes and its control on circulating levels of growth hormone and growth hormone-dependent, insulin-like growth factors (IGF) remains controversial. In the present study, the effect of a 1-wk period of intensive insulin therapy on growth hormone and IGF I and II has been determined in 19 young (age 13–22 yr), insulin-dependent (type I) subjects with diabetes mellitus. IGF I was low during conventional insulin therapy (198 ± 20 versus 438 ± 38 ng/ml in nondiabetic subjects, P < 0.001), and rose within the week of intensified treatment (to 255 ±15 ng/ml, P < 0.005), concomitant with a reduction in plasma glucose from 233 ± 16 to 110 ± 5 mg/dl. IGF I rose despite a significant fall in mean 24-h growth hormone levels from 14.1 ± 2.2 to 9.0 ± 1.2 ng/ml (P < 0.02). The mean IGF II value for the diabetic subjects (504 ± 39 ng/ml) was not significantly different from that of the nondiabetic control group (506 ± 30 ng/ml, P > 0.3) and was not altered by intensified therapy. However, four individual patients with very low IGF I also had depressed IGF II (248 ±16 ng/ml), which was corrected (to 377 ± 35 ng/ml) with improved metabolic control. These data suggest that elevated growth hormone levels in poorly controlled diabetes are ineffective in IGF I generation and that this defect is at least partially corrected by acute improvement in control. The rise in IGF I levels accompanying intensive insulin treatment may suppress the excessive secretion of growth hormone. IGF II levels appear to be affected only by the most severe reductions of growth hormone activity.