SPX and obesity due to melanocortin 4 receptor deficiency: In human, SPX is encoded by the c12orf39 gene (21) and notable drop in serum SPX can be associated with pathological conditions, e.g., type I/type II diabetes (6, 22), obesity (23, 24), metabolic syndrome (25) and polycystic ovary syndrome (26), but the opposite is true for gestational diabetes (27) and psychiatric disorders, e.g., anxiety and anorexia nervosa (28).