IGFBP1 and obesity due to melanocortin 4 receptor deficiency: IGFBP1 sequesters IGF1 reducing bioavailability [47] and an increased IGF1:IGFBP1 ratio [48] and reduced IGFBP1 [49] in serum is associated with obesity, hyperinsulinemia and insulin resistance in human studies and in women with PCOS [50], [51].