Effects of insulin-like growth factor-I on glucose tolerance, insulin levels, and insulin secretion

J Clin Invest. 1992 Jun;89(6):1908-13. doi: 10.1172/JCI115796.


Insulin-like growth factor-I (IGF-I) and insulin interact with related receptors to lower plasma glucose and to exert mitogenic effects. Recombinant human IGF-I (rhIGF-I) was recently shown to decrease serum levels of insulin and C-peptide in fasted normal subjects without affecting plasma glucose levels. In this study we have investigated in six healthy volunteers the responses of glucose, insulin, and C-peptide levels to intravenous rhIGF-I infusions (7 and 14 micrograms/kg.h) during standard oral glucose tolerance tests (oGTT) and meal tolerance tests (MTT), respectively. Glucose tolerance remained unchanged during the rhIGF-I infusions in the face of lowered insulin and C-peptide levels. The decreased insulin/glucose-ratio presumably is caused by an enhanced tissue sensitivity to insulin. The lowered area under the insulin curve during oGTT and MTT as a result of the administration of rhIGF-I were related to the fasting insulin levels during saline infusion (oGTT: r = 0.825, P less than 0.05; MTT: r = 0.895, P less than 0.02). RhIGF-I, however, did not alter the ratio between C-peptide and insulin, suggesting that the metabolic clearance of endogenous insulin remained unchanged. In conclusion, rhIGF-I increased glucose disposal and directly suppressed insulin secretion. RhIGF-I probably increased insulin sensitivity as a result of decreased insulin levels and suppressed growth hormone secretion. RhIGF-I, therefore, may be therapeutically useful in insulin resistance of type 2 diabetes, obesity, and hyperlipidemia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Glucose / metabolism*
  • C-Peptide / blood
  • Food
  • Glucose Tolerance Test
  • Growth Hormone / blood
  • Humans
  • Insulin / blood*
  • Insulin / metabolism
  • Insulin Secretion
  • Insulin-Like Growth Factor I / metabolism
  • Insulin-Like Growth Factor I / physiology*
  • Insulin-Like Growth Factor II / metabolism
  • Male
  • Recombinant Proteins


  • Blood Glucose
  • C-Peptide
  • Insulin
  • Recombinant Proteins
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II
  • Growth Hormone