OBJECTIVE: To investigate the relationship between the circulating level of active ghrelin and abdominal adiposity, serum levels of insulin or insulin resistance in patients with type 2 diabetes mellitus. DESIGN: We measured the plasma levels of the active form of ghrelin in 18 obese and 18 nonobese patients with type 2 diabetes mellitus using a radioimmunoassay (RIA) kit. Body fat accumulation was measured by computed tomography (CT) and insulin resistance by the glucose infusion rate (GIR) during an euglycemic hyperinsulinemic clamp study. RESULTS: Plasma levels of ghrelin in obese patients with type 2 diabetes mellitus were significantly decreased compared with nonobese patients. There were significant correlations between the plasma levels of ghrelin and BMI (r=-0.505, P<0.01), visceral (r=-0.444, P<0.01), subcutaneous (r=-0.506, P<0.01) and total (r=-0.534, P<0.01) fat area, serum levels of insulin (r=-0.513, P<0.01) or GIR (r=0.478, P<0.01) in type 2 diabetic patients. The plasma level of ghrelin was significantly associated with serum levels of insulin (F=8.468, P<0.05) or GIR (F=8.522, P<0.05) after adjustment for BMI in patients with type 2 diabetes mellitus. CONCLUSIONS: Decreased plasma levels of active ghrelin are significantly associated with abdominal adiposity, hyperinsulinemia and insulin resistance in type 2 diabetic patients. Hyperinsulinemia associated with insulin resistance may suppress plasma levels of active ghrelin in patients with type 2 diabetes mellitus.