Growth hormone and insulin-like growth factor regulate insulin-like growth factor-binding protein-1 in Laron type dwarfism, growth hormone deficiency and constitutional short stature

Insulin-like growth factors (IGFs) mediate the effects of growth hormone (GH), and the insulin-like growth factor-binding proteins (IGFBPs) modulate the actions of IGFs in tissues. We studied the circulating levels of IGFBP-1 in 6 children and 9 adults with Laron type dwarfism (LTD), in 11 children and 21 adults with growth hormone deficiency (GHD), and in 8 children with constitutional short stature. Compared with the situation in healthy children, the basal serum IGFBP-1 concentration was 5.4-fold higher in LTD children, 4.1-fold higher in GHD children, and 3.8-fold higher in children with short stature (p<0.02 vs controls in all groups). In adult patients with multiple pituitary hormone deficiency (MPHD), the IGFBP-1 concentration was 2-fold elevated, but it was normal in adult LTD patients. Intravenous (N= 10) or subcutaneous (N=9) administration ofIGF-I (75 μg·kg −1 and 150 μg·kg −1 , respectively) in LTD children resulted in a rapid 50–60% fall in serum insulin (p<0.02), a decline in blood glucose and a concomitant 40–60% rise of IGFBP-1 levels (p<0.05). Treatment for seven days with IGF-I (150 μg·kg −1 ·d −1 ) resulted in a decrease by 34% and 44% of serum IGFBP-1 level in two out of three children with LTD. After prolonged GH therapy, the IGFBP-1 level fell in GHD children by 29% (p<0.05), in GHD adults by 52% (p<0.02) and in children with constitutional short stature by 17% (p<0.02). IGFBP-1 and insulin concentrations were inversely related in patients with GHD (r= −0.66, p<0.001) or with LTD (r= −0.57, p<0.05). Our data suggest that: (a) increased IGFBP-1 concentration in LTD, GHD and constitutional short children may, at least in part, be accounted for by an IGF-I deficiency; (b) both the rise in IGF-I and a fall in insulin contributed to the rise in IGFBP-1 after acute IGF-I administration; (c) prolonged IGF-I or GH treatment causes a persistent decline in IGFBP-1 concentration. In conclusion, IGF-I and GH may regulate IGFBP-1 secretion either directly or via insulin.