What is the Difference Between IGF1 and IGF2

The main difference between IGF1 and IGF2 is that IGF1 mediates the growth promoted by growth hormone (GH) in postnatal life, whereas IGF2 mediates placental and fetal growth. 

IGF1 and IGF2 are two insulin-like growth factors that stimulate the growth and development of vertebrates.  

Key Areas Covered

1. What is IGF1
– Definition, Structure, Function
2. What is IGF2
– Definition, Structure, Function
3. Similarities Between IGF1 and IGF2
– Outline of Common Features
4. Difference Between IGF1 and IGF2
– Comparison of Key Differences

Key Terms 

IGF1, IGF2

What is IGF1

IGF1 (insulin-like growth factor 1) is a hormone with a similar structure to insulin. Another name for IGF1 is somatomedin C. It has a major effect on children’s growth and anabolic effects in adults. The main function of IGF1 is to mediate the effect of growth hormone (GH). The anterior pituitary gland produces the GH. It stimulates the liver to produce IGF1. IGF1 stimulates systemic body growth, promoting the growth of each and every body cell. They include muscle, cartilage, bone, liver, kidney, nerve, skin, hematopoietic, and lung cells. On the other hand, IGF1 stimulates cellular DNA synthesis.

Figure 1: IGF1

Furthermore, IGF1 is a small peptide that contains 70 amino acids. Its molecular weight is 7649 Da. Also, it has an A and B chain connected by a disulfide bond. Its C peptide region has 12 amino acids. Importantly, IGF1 has a similar structure to insulin. However, it has a low affinity to bind insulin receptors. Also, the IGF1 is the gene that encodes the IGF1 peptide. It consists of six exons and two promoters. 

What is IGF2

IGF2 is another peptide hormone that shows structural similarity to insulin. Importantly, it is a major fetal growth factor. The IGF2 is the gene that encodes the IGF2 peptide. It is located in chromosome 11p15.5, a region that contains most imprinted genes. The main function of the IGF2 gene is to promote growth during gestation. Therefore, it promotes the growth and proliferation of cells in fetuses. In IGF2 inheritance, one copy is inherited from the father, and another copy is inherited from the mother. However, the IGF2 gene activity depends on which parent it is inherited from. Therefore, the copy inherited from the father is active, while the copy inherited from the mother is inactive. Therefore, the expression occurs in the paternally inherited gene.

Figure 2: IGF2

Moreover, the function of the IGF2 gene is exerted by binding the IGF2 peptide with the IGF1 receptor. Also, IGF2 binds to the IGF2 receptor, acting as a signaling antagonist that prevents the IGF2 response. During the fetal life, thecal cells produce IGF2 during folliculogenesis. However, IGF2 acts on thecal cells in the form of autocrine signaling. Also, it acts on granulosa cells in the paracrine manner. Significantly, IGF2 promotes the proliferation of granulosa cells during the follicular phase of the menstrual cycle. Also, after ovulation, IGF2 promotes progesterone secretion in the menstrual cycle’s luteal phase. 

Similarities Between IGF1 and IGF2

• IGF1 and IGF2 are two insulin-like growth factors that mediate the growth.
• They occur in vertebrates.
• Also, they show a similar structure to insulin.
• Both are peptide hormones. 

Difference Between IGF1 and IGF2

Definition

IGF1 refers to a hormone that manages the effects of growth hormone (GH) in the body, while IDF2 refers to a peptide hormone regulating various cellular processes such as proliferation and apoptosis.

Types

IGF1 is a major growth factor in adults, while AGF2 is a major growth factor in fetuses.

Involvement of GH

IGF1 mediates the action of growth hormone (GH), while IGF2 does not mediate the action of growth hormone (GH). 

Conclusion

In brief, IGF1 and IGF2 are two insulin-like growth factors. They are protein hormones. Their function is to regulate growth. IGF1 is a major growth factor in adults. It mediated the effect of GH. In comparison, IGF2 is a major growth factor in fetuses. However, it does not mediate the effect of GH. Therefore, the main difference between IGF1 and IGF2 is their type.

References:

1. Laron Z. Insulin-like growth factor 1 (IGF-1): a growth hormone. Mol Pathol. 2001 Oct;54(5):311-6. doi: 10.1136/mp.54.5.311. PMID: 11577173; PMCID: PMC1187088.
2. S. National Library of Medicine. (n.d.-b). IGF2 gene: Medlineplus genetics. MedlinePlus. 

Image Courtesy:

1. “Protein IGF1 PDB 1bqt” By Emw – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Protein IGF2 PDB 1igl” By Emw – Own Work (CC-BY SA 3.0) via Commons Wikimedia