ACUTE AND CHRONIC REGULATION OF SERUM SEX HORMONE-BINDING GLOBULIN LEVELS BY PLASMA-INSULIN CONCENTRATIONS IN MALE NONINSULIN-DEPENDENT DIABETES-MELLITUS PATIENTS

This study was undertaken to investigate the relationship of the serum sex hormone-binding globulin (SHBG) levels with the plasma insulin co ncentration and with the insulin resistance in male subjects with noni nsulin-dependent diabetes mellitus (NIDDM). This investigation compris ed 12 patients with NIDDM and 16 normal subjects matched for age, sex, and body mass index (BMI). There was a significant increase in insuli n levels (P < 0.03) and a decrease in SHBG levels (P < 0.01) in the di abetic group as compared with those of the normal group. The sex hormo ne and plasma insulin levels were measured in NIDDM patients undergoin g exercise and dietary therapy. Insulin sensitivity was evaluated by t he hyperinsulinemic euglycemic clamp technique expressed as the glucos e infusion rate (GIR) before and after the treatment. The SHBG levels correlated significantly with the insulin concentrations (r = -0.643, P < 0.05) and with the GIR (r = 0.615, P < 0.05) before the treatment. The SHBG levels (P < 0.02) and GIR (P < 0.01) increased, and the insu lin concentrations (P < 0.01) decreased significantly during the treat ment. The SHBG levels showed a negative and significant correlation wi th the plasma insulin concentrations at the end of the clamp study bef ore (r = -0.615, P < 0.05) and after (r = -0.626, P < 0.05) the treatm ent. These findings suggest that, in the hyperinsulinemic state, plasm a insulin has a direct effect on the SHBG levels. SHBG levels decrease d significantly during the clamp study before (P < 0.02) and after (P < 0.01) the treatment. This may represent the acute effect of insulin on the SHBG levels. Briefly, these results suggest that insulin may di rectly affect the SHBG levels and that SHBG may constitute an index of the insulin resistance only in the hyperinsulinemic state.