Comparison of various insulin sensitivity indices in psoriatic patients and their relationship with type of psoriasis.

Aim: We aimed to identify insulin resistance and its possible association with types, duration and severity of psoriasis, and to evaluate various simple insulin-sensitivity indices and beta-cell function in psoriasis.

Methods: A cross-sectional study was performed in 110 non-obese adults (18-50 years old): 70 with psoriasis (53 type I, 17 type II psoriasis) and 40 healthy individuals. Blood glucose, insulin and C-peptide levels were measured. Oral glucose tolerance test (OGTT); insulin sensitivity and beta-cell function indices derived from a single sample and OGTT were determined and compared in three groups.

Results: Total, type I and type II psoriatics had IGT rates of 18.6%, 13.2% and 40%, respectively. In the control group IGT was only 2.5%. Homeostasis Model Assessment (HOMA) beta cell index, fasting insulin, Raynaud index, HOMA-IR and FIRI results were higher in total, type I and type II psoriatics than in controls (P < 0.05, for all). Fasting Belfiore index, QUICKY index, ISI HOMA and FIRI(-1) results were lower in total, type I and type II psoriatics than in controls (P < 0.05, for all), and type I psoriatics had higher levels of these indices than type II psoriatics (P < 0.05, for all).

Conclusion: Our study showed that psoriatic patients were more insulin resistant than healthy subjects and type II psoriatics were more susceptible than type I psoriatics to develop IGT. We suggest that beta-cell function and insulin sensitivity indices are useful methods for measuring insulin resistance in psoriatics. We propose that OGTT should be applied especially in type II psoriatics because of increased rate of IGT in this group.