CHI3L1 and obesity due to melanocortin 4 receptor deficiency: In this, however, the mean values of circulating YKL-40 in healthy lean subjects (18.9 ± 5.3 (SEM) ng/mL) and in obese subjects with NGT (approximately 24 ng/mL) were rather low compared to other studies regarding obesity [12, 14] and also compared to studies regarding YKL-40 levels in healthy subjects [29] and in the general population [30].