Insulin resistance in psoriasis.
The oral glucose tolerance test (OGTT) and intravenous insulin tolerance test (15-min ITT) were applied to ten patients with psoriasis and to 11 control subjects. No significant differences in mean plasma glucose levels were detected between psoriatic patients and normal individuals. In contrast, serum insulin levels were significantly higher for the psoriatic patients as compared to the controls at 30, 60 and 120 min during the OGTT (P < 0.05). The glucose disappearance rate during the 15-min ITT was lower in patients with psoriasis than in controls (5.1 +/- 0.5%/min vs 7.5 +/- 0.4%/min, P < 0.05), demonstrating a state of insulin resistance. Interestingly, the reduction in serum potassium levels during the ITT was also lower in the patients than in the controls (0.6 +/- 0.06 mEq/l vs 1.06 +/- 0.07 mEq/l, P < 0.05), suggesting that the insulin resistance observed in psoriasis is not only related to glucose metabolism, but also to another important action of insulin, namely extrarenal potassium homeostasis.