Insulin sensitivity assessment with euglycemic insulin clamp in adult beta-thalassaemia major patients.

Objective: To assess insulin sensitivity in young adult normoglycemic beta-thalassaemia major patients.

Methods: We measured insulin sensitivity with the euglycemic insulin clamp in 10 young adult (mean age 24.85 +/- 2.45 yrs) normoglycemic beta-thalassaemia major patients and 10 sex- & age-matched controls. Liver iron accumulation was assessed by magnetic resonance imaging (MRI).

Results: Glucose infusion rate (M) required to maintain euglycemia was significantly reduced in thalassaemic patients compared to controls (261.5 +/- 63.5 mg/m2 x min vs. 355.6 +/- 35.3 mg/m2 x min, P = 0.008). Consequently, significantly reduced in the thalassaemic group were also tissue sensitivity to insulin (M/I(s-s)) and glucose metabolic clearance rate (M/G(s-s)). There was significant negative correlation between ferritin levels and glucose infusion rate (r = -0.918 P = 0.004). No significant correlations were observed between age, body mass index, daily transfusional iron accumulation, liver iron content and any of the euglycemic clamp parameters. Fasting insulin levels were significantly increased in patients with beta-thalassaemia major compared to controls (P = 0.01), and had significant negative correlation to MRI-derived liver iron content (r = -0.733, P = 0.03).

Conclusions: Our data indicate that reduced insulin sensitivity resulting in hyperinsulinaemia precedes the manifestation of glucose intolerance in patients with beta-thalassaemia major. Insulin resistance seems to correlate with increased serum ferritin levels.