Growth hormone-insulin-like growth factor-I axis in adult insulin-dependent diabetic patients: Evidence for central hypersensitivity to growth hormone-releasing hormone and peripheral resistance to growth hormone

The aim of this study was to assess the GH-IGFI axis, GH receptor availability, as reflected by the levels of GH-BP, and the amount of GH-dependent IGFBP-3 in adult IDDM patients with different degrees of metabolic control. Thus, 10 adult well-controlled IDDMs (HbA1 7.8 +/- 0.4%), 10 adult non-ketotic poorly controlled IDDMs (HbA1 13.3 +/- 7%) and 14 sex- and age-matched healthy controls were subjected to two intravenous GH-RH stimulation tests with 0.1 and 1.0 mu g/kg body weight respectively, and a plasma IGF-1 generation test induced by the administration of hGH, Poorly controlled IDDM patients exhibited an exaggerated GH reponse to 1.0 mu g/kg of GH-RH when compared to healthy control subjects. Low fasting plasma IGF-1 levels and a blunted IGF-1 response to exogenously administered hGH were also found in poorly controlled IDDMs when compared to the healthy control group. GH-BP levels were significantly lower in IDDMs than in normal controls, and correlated positively with the IGF-1 generation capacity after hGH. Serum IGFBP-3 levels measured by RIA were similar in IDDM and control groups. Good glycemic control for 5.7 +/- 0.9 months did not correct the above mentioned abnormalities of the GH-IGF-1 axis. Our findings suggest that IDDM is associated with a diminished availability of GH receptors and synthesis of IGF-1. CH might then increase as a compensatory mechanism, further down-regulating liver GH receptors, and thus perpetuating the initial abnormality.