Insulin increases plasma somatomedin C (IGF-1) concentrations in adult type 1 diabetic patients.
The role of insulin in the control of somatomedin release has been investigated in people with Type 1 diabetes. Six patients underwent insulin-induced hypoglycaemia of 20 min duration and 8 patients were studied using the hyperinsulinaemic euglycaemic clamp technique at insulin infusion rates of 0.25, 1.25, 2.5, and 0.25 mU kg-1 min-1 for 1 h at each rate. In the first study plasma insulin concentrations rose from (median, range) 23 (10-36) to 114(60-200) mU l-1 at the onset of hypoglycaemia, and fell to 53 (23-100) mU l-1 after 20 min hypoglycaemia and 30 (15-73) mU l-1 on return to normoglycaemia. Plasma IGF-1 rose from 140 (96-292) to 179 (127-352) micrograms l-1 (p less than 0.05) at the onset of hypoglycaemia and fell to 131 (125-173) micrograms l-1 after 20 min and to 154 (121-287) micrograms l-1 at the end of the study. During hyperinsulinaemia plasma insulin rose from 23 (19-40) mU l-1 at the lowest infusion rate to 61 (33-84) and 148 (68-200) mU l-1 at the two higher infusion rates. Over the same period, plasma IGF-1 increased from 91 (13-203) to 123 (98-182) micrograms l-1 (p less than 0.05) and 109 (84-160) micrograms l-1. There was no correlation between growth hormone levels and IGF-1 in either study. These results suggest that insulin produces short-term increases in IGF-1 levels in man in the absence of a growth hormone response.
Grant
P J
PJ
University Department of Medicine, General Infirmary, Leeds, UK.
Stickland
M H
MH
Bristow
A F
AF
Clarke
R F
RF
Wales
J K
JK
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000502:physiology; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007332:Insulin Infusion Systems; D007334:Insulin-Like Growth Factor I / Q000097:blood*; D013002:Somatomedins / Q000097:blood*
D001786:Blood Glucose; D007328:Insulin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I