EPO and obesity due to melanocortin 4 receptor deficiency: SP can be congenital, caused by erythropoietin (EPO) receptor mutations, or acquired and induced by physiological changes that raise the body demand for oxygen, such as renal, lung and heart disease, high altitudes, severe obesity, defective oxygen transport, and EPO overproduction caused by certain kidney diseases or secretion by some tumors8–10.