What is the Difference Between IGF1 and IGF2?

Insulin-like growth factors 1 and 2 (IGF1 and IGF2) are both involved in promoting growth and development in vertebrates. However, they have distinct roles and characteristics:

1. Origin: IGF1 is primarily produced in the liver and plays a crucial role in postnatal growth and development in mammals. In contrast, IGF2 stimulates placental and fetal growth and is not regulated by growth hormone.
2. Receptors: Both IGF1 and IGF2 signal through the IGF1 receptor (IGF1R), leading to growth and metabolic effects via the downstream PI3K/Akt pathway. IGF2 also has a receptor of its own, IGF2R, but its role is not well understood.
3. Affinity to Insulin Receptors: IGF1 has a higher affinity for the human insulin-like growth factor 1 receptor (IGF1R) and hybrid receptors, while IGF2 has a lower affinity. However, IGF1 and IGF2 have up to fivefold differences in their binding affinity to the two insulin receptor isoforms, IR-A and IR-B.
4. Local vs. Endocrine Action: Both IGF1 and IGF2 have a dual mode of action as local and endocrine growth factors. Local IGFs are produced throughout the body, whereas endocrine IGFs are mainly produced by the liver.

In summary, both IGF1 and IGF2 are essential for growth and development, but they have different origins, receptors, and binding affinities. IGF1 is mainly liver-derived and plays a crucial role in postnatal growth, while IGF2 stimulates placental and fetal growth.

Comparative Table: IGF1 vs IGF2

IGF1 (Insulin-like Growth Factor 1) and IGF2 (Insulin-like Growth Factor 2) are two peptide hormones that play crucial roles in growth and development. They are both less potent than insulin but have similar structures and functions. Here is a table summarizing the differences between IGF1 and IGF2:

IGF1 is a major growth factor in adults, while IGF2 is the major growth factor in the fetus. IGF1 production primarily occurs in the liver, whereas IGF2 production occurs in a wide variety of somatic tissues during the early embryonic stage. IGF1 production is highly dependent on the secretion of growth hormone, while IGF2 production is less dependent on it.

IGF1 and IGF2 have different affinities for insulin receptor isoforms (IR-A and IR-B). IGF1 activates both IR-A and IR-B with similar affinity, while IGF2 activates IR-B more effectively than IR-A.