biology

Insulin-like growth factor 1

Insulin-like growth factor 1 is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Insulin-like growth factor 1 rather than just read about it. In short: Insulin-like growth factor 1 (IGF1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults. In the 1950s IGF1 was called "sulfation factor" because it stimulated sulfation of cartilage in vitro, and in the 1970s due to its effects it was termed "nonsuppressible insulin-like activity" (NSILA).

Key takeaways

Insulin-like growth factor 1 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Insulin-like growth factor 1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Insulin-like growth factor 1 from memory before moving on to harder problems.

Reference excerpt

Insulin-like growth factor 1 (IGF1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults. In the 1950s IGF1 was called "sulfation factor" because it stimulated sulfation of cartilage in vitro, and in the 1970s due to its effects it was termed "nonsuppressible insulin-like activity" (NSILA). IGF1 is a protein that in humans is encoded by the IGF1 gene. IGF1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges. IGF1 has a molecular weight of 7,649 daltons. In dogs, an ancient mutation in IGF1 is the primary cause of the toy phenotype. IGF1 is produced primarily by the liver. Production is stimulated by growth hormone (GH). Most of IGF1 is bound to one of 6 binding proteins (IGF-BP). IGFBP-1 is regulated by insulin. IGF1 is produced throughout life; the highest rates of IGF1 production occur during the pubertal growth spurt. The lowest levels occur in infancy and old age. Low IGF1 levels are associated with cardiovascular disease, while high IGF1 levels are associated with cancer. Mid-range IGF1 levels are associated with the lowest mortality. A synthetic analog of IGF1, mecasermin, is used for the treatment of growth failure in children with severe IGF1 deficiency. Cyclic glycine-proline (cGP) is a metabolite of hormone insulin-like growth factor-1 (IGF1). It has a cyclic structure, lipophilic nature, and is enzymatically stable which makes it a more favourable candidate for manipulating the binding-release process between IGF1 and its binding protein, thereby normalising IGF1 function.

Synthesis and circulation

The polypeptide hormone IGF1 is synthesized primarily in the liver upon stimulation by growth hormone (GH). It is a key mediator of anabolic activities in numerous tissues and cells, such as growth hormone-stimulated growth, metabolism and protein translation. Due to its participation in the GH-IGF1 axis it contributes among other things to the maintenance of muscle strength, muscle mass, development of the skeleton and is a key factor in brain, eye and lung development during fetal development. Studies have shown the importance of the GH/IGF1 axis in directing development and growth, where mice with an IGF1 deficiency had a reduced body- and tissue mass. Mice with an excessive expression of IGF1 had an increased mass.

The levels of IGF1 in the body vary throughout life, depending on age, where peaks of the hormone is generally observed during puberty and the postnatal period. After puberty, when entering the third decade of life, there is a rapid decrease in IGF1 levels due to the actions of GH. Between the third and eighth decade of life, the IGF1 levels decrease gradually, but unrelated to functional decline. However, protein intake is proven to increase IGF1 levels.

Mechanism of action

IGF1 is a primary mediator of the effects of growth hormone (GH). Growth hormone is made in the anterior pituitary gland, released into the bloodstream, and then stimulates the liver to produce IGF1. IGF1 then stimulates systemic body growth, and has growth-promoting effects on almost every cell in the body, especially skeletal muscle, cartilage, bone, liver, kidney, nerve, skin, hematopoietic, and lung cells. In addition to its insulin-like effects (insulin being the main anabolic hormone in the body), IGF1 can also regulate cellular DNA synthesis. IGF1 binds to at least two cell surface receptor tyrosine kinases: the IGF1 receptor (IGF1R), and the insulin receptor. Its primary action is mediated by binding to its specific receptor, IGF1R, which is present on the surface of several cell types in a multitude of tissues. Binding to the IGF1R initiates intracellular signaling. IGF1 is one of the most potent natural activators of the Akt signaling pathway, a stimulator of cell growth and proliferation, and a potent inhibitor of programmed cell death. The IGF1 receptor and insulin receptor are two closely related members of a transmembrane tetrameric tyrosine kinase receptor family. They control vital brain functions, such as survival, growth, energy metabolism, longevity, neuroprotection and neuroregeneration.

Metabolic effects As a major growth factor, IGF1 is responsible for stimulating growth of all cell types, and causing significant metabolic effects. One important metabolic effect of IGF1 is signaling cells that sufficient nutrients are available for them to undergo hypertrophy and cell division. Its effects also include inhibiting cell apoptosis and increasing the production of cellular proteins. IGF1 receptors are ubiquitous, which allows for metabolic changes caused by IGF1 to occur in all cell types. IGF1's metabolic effects are far-reaching and can coordinate protein, carbohydrate, and fat metabolism in a variety of different cell types. The regulation of IGF1's metabolic effects on target tissues is also coordinated with other hormones such as growth hormone and insulin.

The IGF system IGF1 is part of the insulin-like growth factor (IGF) system. This system consists of three ligands (insulin, IGF1 and IGF-2), two tyrosine kinase receptors (insulin receptor and IGF1R receptor) and six ligand binding proteins (IGFBP 1–6). Together they play an essential role in proliferation, survival, regulation of cell growth and affect almost every organ system in the body. Similarly to IGF1, IGF2 is mainly produced in the liver and after it is released into circulation, it stimulates growth and cell proliferation. IGF2 is thought to be a fetal growth factor, as it is essential for a normal embryonic development and is highly expressed in embryonic and neonatal tissues.

Variants A splice variant of IGF1 sharing an identical mature region, but with a different E domain is known as mechano growth factor (MGF).

Related disorders

Laron syndrome

Acromegaly Acromegaly is a syndrome caused by the anterior pituitary gland producing excess growth hormone (GH). A number of disorders may increase the pituitary's GH output, although most commonly it involves a tumor called pituitary adenoma, derived from a distinct type of cell (somatotrophs). It leads to anatomical changes and metabolic dysfunction caused by elevated GH and IGF1 levels. High level of IGF1 in acromegaly is related to an increased risk of some cancers, particularly colon cancer and thyroid cancer.

Use as a diagnostic test

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Illustrations

Worked examples

Example 1 — a first encounter with Insulin-like growth factor 1

Start with the simplest possible case. Write down what Insulin-like growth factor 1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Insulin-like growth factor 1 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Insulin-like growth factor 1 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Insulin-like growth factor 1

In research: Insulin-like growth factor 1 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Insulin-like growth factor 1 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Insulin-like growth factor 1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aging-related proteins, Developmental neuroscience, Genes on human chromosome 12, so understanding it makes those chapters shorter.
In everyday life: Look for Insulin-like growth factor 1 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Insulin-like growth factor 1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Insulin-like growth factor 1 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Insulin-like growth factor 1 in simple terms?

Why does Insulin-like growth factor 1 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Insulin-like growth factor 1?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Insulin-like growth factor 1.