Science commentary: Insulin-like growth factor and cognitive function

Insulin-like growth factors (IGFs) are peptides that regulate the growth, metabolism, survival, and differentiation of cells and are regulated by growth hormone. Both IGF-I and IGF-II consist of small peptides that share about 50% homology with proinsulin and are produced chiefly by the liver. IGF-I is an important cell growth regulator, but the role of IGF-II is less clear. IGF-II acts mainly via IGF-I receptors; IGF-II receptors do exist, but their role is believed simply to …