In 1971, two research teams identified the insulin receptor by observing the binding of 125I-labeled insulin to the membranes of adipose tissue and liver cells.23,24 And in the following few years, the interactions between insulin and insulin receptors in various healthy or pathological states, like obesity and diabetes, had been elucidated.25–30. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.