SHC1 gene encodes three isoforms of 66, 52 and 46 kDa; while p46Shc and p52Shc isoforms are coupled to growth and survival signals, p66Shc mediates pro-apoptotic responses to oxidative stress59 being considered as a negative determinant of life span due to its effects on mTOR/S6K cascade promoting obesity and IR60. This evidence concerns the gene SHC1 and obesity due to melanocortin 4 receptor deficiency.