LEP and kidney failure: However, there were no significant differences of leptin levels in patients with impaired renal function (defined as a serum creatinine value above 1.1 mg/dl) compared to patients with a regular renal function (defined as a serum creatinine value below or equal than 1.1 mg/dl) (patients with renal failure, leptin mean 29282 pg/ml, ± SEM 4398 pg/ml, n = 75; patients without renal failure, leptin mean 21896 pg/ml, ± 5631 pg/ml, n = 29; p = 0.3).