CHI3L1 and endothelial dysfunction: In a study by Hanafy et al. investigating serum YKL-40 levels in male patients diagnosed with idiopathic infertility, they measured serum YKL-40 levels in patients with varicocele to evaluate the role of endothelial dysfunction in these patients and reported higher serum YKL40 levels in these patients as compared to the controls [14].