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Insulin-like growth factors (IGF)

Insulin-like growth factors (IGF) are protein hormones in Anatomy and Physiology I that help carry out growth hormone’s effects on cell growth, division, and survival.

Last updated July 2026

What are insulin-like growth factors (IGF)?

Insulin-like growth factors (IGF) are hormone-like proteins in Anatomy and Physiology I that help the body grow by carrying out many of the effects of growth hormone. They are called “insulin-like” because their structure is similar to insulin, but their main job here is not blood sugar control. Instead, IGFs act as signals that tell cells to grow, divide, and stay alive longer.

The best-known IGF is IGF-1, which is strongly linked to growth hormone from the pituitary gland. Growth hormone stimulates tissues, especially the liver, to make IGF-1. Then IGF-1 travels through the bloodstream and helps tissues throughout the body respond with increased cell production and tissue growth. That chain is a classic endocrine pathway: one gland releases a hormone, another tissue makes a second signal, and that second signal creates the larger body effect.

IGFs matter most during childhood, adolescence, and tissue repair. They help bones lengthen, muscles build, and other tissues develop normally. They also support cell differentiation, which means immature cells become more specialized so they can do their assigned jobs in the body. Without that signaling, growth and development would be slower or incomplete.

IGFs do not work alone. Their activity is shaped by growth hormone levels, nutrition, and overall body condition. For example, if someone is undernourished, the body may not make or use IGF-1 as effectively, even if growth hormone is present. That is one reason growth is tied to both hormones and general health, not just one gland.

Another useful way to think about IGF is that it turns a “grow now” message into a cellular response. Growth hormone starts the signal, but IGF helps translate that signal into actual changes in tissues. In A&P, that makes IGF a good example of how the endocrine system uses multiple steps to keep growth, repair, and homeostasis coordinated.

Why insulin-like growth factors (IGF) matter in Anatomy and Physiology I

IGF shows up anywhere you trace how the endocrine system controls body growth. In Anatomy and Physiology I, it connects the pituitary gland, growth hormone, and target tissues into one pathway instead of treating them as separate facts. If you can explain IGF, you can explain why a hormone released in one place can lead to changes in bones, muscles, and other tissues somewhere else.

It also helps you separate similar ideas that get mixed together in class. Growth hormone is the signal from the pituitary, while IGF is one of the main downstream messengers that produces the growth response. That distinction is useful when you are labeling diagrams, comparing hormone functions, or answering questions about what happens before and after a gland releases a hormone.

IGF also connects to cell differentiation and survival, so it is not only about making the body bigger. It is about how tissues develop, repair themselves, and maintain normal structure. That makes it a useful term when you study development, healing, and disorders of growth. If a case asks why a child is not growing normally or why a growth-related hormone pathway is disrupted, IGF is part of the explanation.

How insulin-like growth factors (IGF) connect across the course

Growth Hormone (GH)

Growth hormone is the upstream hormone that helps trigger IGF production. In a normal endocrine pathway, GH comes from the pituitary gland and signals tissues, especially the liver, to release IGF-1. If you mix up the two, it gets hard to explain what starts the response and what actually carries it out in the body.

Pituitary Gland

The pituitary gland is the source of growth hormone, so it sits earlier in the control chain than IGF. When you trace hormone regulation, the pituitary is the gland that initiates the growth signal, while IGF helps spread and amplify that signal to target tissues. That makes the pituitary the starting point in many growth-related diagrams.

Cell Differentiation

IGF supports cell differentiation by helping cells mature into specialized types during growth and repair. That means it affects not just how many cells you have, but what those cells become and how well they function. In class, this connection often comes up when you study development, tissue growth, or healing after injury.

adipose tissue

Adipose tissue is one of the body tissues influenced by endocrine signals, including growth-related pathways. It is not the main target you usually focus on for IGF, but it helps show that hormones affect more than one tissue type. When you study body composition and metabolism, it helps to remember that growth signals and energy balance often overlap.

Are insulin-like growth factors (IGF) on the Anatomy and Physiology I exam?

A quiz question may give you a hormone pathway and ask you to trace what happens after the pituitary releases growth hormone. That is where IGF comes in: you identify it as the downstream mediator that helps tissues grow and cells differentiate. On a labeled diagram, you might need to place IGF between GH and body tissues, or explain why a growth signal produces skeletal and muscular changes. In short-answer and case questions, use IGF when the prompt is about growth, repair, or abnormal development, not simple blood sugar control.

Key things to remember about insulin-like growth factors (IGF)

  • Insulin-like growth factors are hormone-like proteins that help carry out growth hormone’s effects in the body.

  • IGF-1 is the best-known form and is strongly linked to tissue growth, cell division, and cell survival.

  • In the growth pathway, the pituitary gland releases growth hormone first, and IGF helps turn that signal into actual body changes.

  • IGF matters for bone growth, muscle development, and normal tissue repair, especially during childhood and adolescence.

  • Do not confuse IGF with insulin, because its main job in this course is growth signaling, not blood glucose regulation.

Frequently asked questions about insulin-like growth factors (IGF)

What is insulin-like growth factors (IGF) in Anatomy and Physiology I?

Insulin-like growth factors are proteins that help the body grow by mediating many of growth hormone’s effects. They promote cell growth, cell division, and cell survival, especially in tissues that are developing or repairing. IGF-1 is the most commonly discussed form in A&P.

How are IGF and growth hormone related?

Growth hormone is the signal that starts the pathway, and IGF is one of the main downstream messengers that produces the growth response. The pituitary releases growth hormone, then target tissues, especially the liver, make IGF. That is why IGF is often described as the mediator of growth hormone’s effects.

Does IGF do the same thing as insulin?

No. They are similar in structure, which is why IGF got its name, but they do different jobs in this course. Insulin mainly regulates blood glucose, while IGF is tied to growth, development, and cell survival.

Why would a teacher ask about IGF in an Anatomy and Physiology quiz?

Because IGF is a good example of endocrine signaling and tissue growth. A question might ask you to trace a hormone pathway, explain how growth hormone affects the body, or connect a hormone to cell differentiation and development. It is a small term with a big place in the growth axis.

Insulin-Like Growth Factors (IGF) | Anatomy | Fiveable