This study was designed to evaluate insulin sensitivity, proinflammatory markers and adiponectin concentration in young males with different subtypes of depressive disorder.Nonobese young males with depressive disorder (ages between 18 years and 30 years; body mass index, BMI < or = 25 kg/m(2)) were recruited and divided into reactive depression (RD, N = 14), major depression (MD, N = 21) and bipolar depression (BD, N = 15) based on clinical course and symptom changes in Hamilton rating scale for depression (HAM-D). Fourteen age- and BMI-matched healthy males were enrolled as controls. All of the participants received a 75-g oral glucose tolerance test (OGTT). Insulin sensitivity and beta-cell function were calculated by minimal model method from the frequently sampled intravenous glucose tolerance test. Plasma C-reactive protein (CRP), adiponectin, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were determined.Compared to the controls, insulin sensitivity (S(I)) were significantly lower in MD and BD (0.78 +/- 0.09 min(-1)/pmol and 0.75 +/- 0.09 min(-1)/pmol vs. 1.09 +/- 0.08 x 10(-5) min(-1)/pmol, P < 0.05, respectively). Acute insulin response (AIR) to intravenous glucose was elevated in BD as compared to control and RD groups (6079.9 +/- 841.8 pmol vs. 3339.8 +/- 356.4 pmol and 3494.8 +/- 337.7 pmol, P < 0.05, respectively). Plasma adiponectin level was diminished in BD group as compared to the control and RD groups (7.41 +/- 0.45 microg/ml vs. 9.07 +/- 0.54 microg/ml and 9.38 +/- 0.46 microg/ml; P < 0.05 and P < 0.01, respectively). By regression analysis, a significantly negative correlation between HAM-D score and S(I) was found in MD (r = -0.60, P = 0.005) and BD groups (r = -0.57, P = 0.04).The results suggest that there is an inverse relationship between both major and bipolar depression and insulin resistance in nonobese young males.