Endothelin and leptin within serum, and myeloperoxidase and midkine within urine, seemed to be more involved in women’s MDD pathophysiology, whereas apolipoprotein A1, EGF and myeloperoxidase within serum and cortisol, substance P and thromboxane B2 seemed to be more involved within men′s MDD pathophysiology. The gene discussed is MDK; the disease is major depressive disorder.