IGF1 and diabetes mellitus: Tyrosine phosphorylation of IRS-1 is known to be an important step in the propagation of the insulin/IGF-1 signal, while the role of serine and threonine phosphorylation of IRS-1 has recently become of more significance as a component of insulin resistance, since decreased insulin/IGF-1 signaling is likely a key factor in diabetes [19-23].