The involvement of growth hormone-binding protein in altered GH-IGF axis in IDDM

Abstract

High GH and low IGF-I are well known in IDDM patients. To delineate this altered GH-IGF-I axis in IDDM, we investigate the role of GH-binding protein (GHBP) in relation to the metabolic and nutritional states. Materials and Methods: Forty seven patients with IDDM, mean 13.7 years, were evaluated. Blood samples were obtained before insulin injection and breakfast to test for plasma glucose (PG), IGF-I, IGFBP-1, IGFBP-3, total and complex GHBP (tGHBP and cGHBP), and HbA(1C). Urine samples were collected in the morning for urinary GH (uGH). The difference between tGHBP and cGHBP is defined as fGHBP. The levels of PG and HbA(1C) were not correlated with each level of tGHBP, cGHBP, fGHBP or uGH. The levels of tGHBP, cGHBP and fGHBP were not all correlated with uGH. Both the levels of IGF-I and body mass index (BMI) were positively correlated with fGHBP. The duration of IDDM was negatively correlated with tGHBP, cGHBP and fGHBP. Discussion: As the previous report of the relationship between GH binding reserve to GHBP and IGF-I or BMI in nondiabetic subjects, fGHBP again showed statistical links with these parameters in IDDM. We therefore suggest that GHBP, especially its free form, may reflect a malmetabolic state of IDDM liver, resulting in an altered GH- IGF-I axis.