What are Growth Factors? What are They Important?

May 21, 2015

Growth factors are natural substances made by the human body that play a variety of vital functions, including the regulation and stimulation of cellular growth, reparation, and differentiation.

Everything You Need to Know About Growth Factors

Because of their roles in cellular growth (and therefore muscle growth), growth factors are well-known for having a particularly important function in exercise and physical fitness. However, they are also widely used and experimented on in clinical research, and have been increasing prevalent in medical treatments such as:

  • Therapy for neutropia (low white blood cell count)
  • Bone marrow transplants
  • Formation of new blood vessels for cardiovascular diseases
  • Treatment for leukemia and other cancers

What Are Growth Factors?

Growth factors occupy the same biological categorization as proteins, amino acids and naturally occurring steroid hormones. Like these other biochemical compounds, they mostly act as signaling molecules, binding to a target receptor and catalyzing a certain cellular response such as healing or proliferation.

Growth factors were discovered in 1952 by Rita Levi-Montalcini as part of her research on cancer cell growth. Her research, deduced that the tumor she had been experimenting on was secreting a substance that stimulating cancerous nerve fibers. This groundbreaking discovery marked the isolation of the first growth factor, nerve growth factor (or NGF), which earned Levi-Montalcini the 1986 Nobel Prize in Physiology or Medicine.

Insulin-Like Growth Factors

There are hundreds of growth factors, which are grouped into dozens of classes such as fibroblast growth factors and myostatin. One particular group, insulin-like growth factors, continues to be particularly important in research for the roles they play in physiological development. If you have been browsing through an online peptide shop, you may already be acquainted with some of these “IGFs” — if not, here is everything you need to know about IGF-2 and IGF-1, as well as the latter’s splice variant, MGF.


IGF-1 stands for insulin-like growth factor-1 (also sometimes referred to a somatomedin C). Made of 70 amino acids, it is a protein similar in structure to insulin that binds to its corresponding receptor: insulin-like growth factor receptor I. IGF-1 is primarily produced as a trophic hormone by the liver, which means it signals cellular growth from the endocrine system. It is likewise closely associated with other endocrine functions and bears clinical relevance to a variety of hormonal and growth failures, including dwarfism, gigantism, and acromegaly (abnormal growth in the feet, hands and face).


IGF-2 is insulin-like growth factor-2. Like IGF-1, it bears a structural resemblance to insulin, and also has a significant dependence on the human growth hormone (i.e. somatropin). IGF-2 has the same function of regulating growth and certain endocrine functions as IGF-1, but has also recently been linked to psychological phenomena such as fear, memory and anxiety. In addition, IGF-2 promotes the growth of prenatal beta cells that produce insulin in the pancreas, and as such is currently thought to be linked to type I diabetes.

IGF-2 vs. IGF-1

Insulin-like growth factors 1 and 2 are alike and both closely associated with one another. They are primarily secreted by the liver and circulated in blood, and both are similar to insulin in form. The primary distinction between these two growth factors is the phase in physiological development during which each is most significant. The role played by IGF-2 is more salient in fetal growth and development, while IGF-1 is more important in the development of adults, but is also not age-specific per se.

In addition to their functions in physiological development, another noteworthy distinction between IGF 1 and 2 is their interaction with cell surface receptors. Of the two, only IGF-2 can bind to both insulin-like growth factor receptors II and I. Being a signaling antagonist, the IGF-II receptor suppresses growth factor responses when bound to IGF-2. It is during this binding that the insulin-like growth factor manifests itself.


MGF, also known as IGF-1Ec, stands for mechano growth factor, a splice variant of IGF-1. This alternate splice comes from a variation in the amino acid coding, in which the E-domain of its C-terminus sequence is seconded by additional nucleotide sequences. In RNA form, MGF is expressed in muscle tissues, in which it increases stem cell count and allows for muscle fibers to fuse and mature in response to overload.

MGF vs. IGF-1

Because it shares an identical mature region as IGF-1, MGF should not be thought as an entirely separate growth factor. Nevertheless, its distinct E-domain allows MGF to act on muscles in a particular manner. The splicing of IGF-1 is a response to overload activates satellite cells, which then stimulates the undamaged nuclei into growing new muscle tissue and fiber. The hypertrophic function of the mechano growth factor makes it a distinctly necessary component of adult muscle growth.


Growth factors have been, and will continue to be, extremely important in both ordinary human health and the treatment of a variety of medical conditions. Significant health and endocrine disorders notwithstanding, the best thing you can do for your growth factors is to live well: eat right, exercise, and take care of your body. New and exciting research is being done on these extraordinary molecules every day, preventing and treating diseases and potentially saving the lives of millions!

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