IGF-1 (Insulin-like Growth Factor 1) Test

This test measures the amount of IGF-1 (insulin-like growth factor 1) in your blood. IGF-1 is a hormone, a chemical messenger in your bloodstream that controls the actions of certain cells or organs. IGF-1 manages the effects of growth hormone (GH) in your body.

Together, IGF-1 and GH promote normal growth of bones and tissues. GH levels in the blood change throughout the day, depending on your diet and activity levels. But IGF-1 levels are more stable.

So, a reliable way to track GH in your body is by measuring the level of IGF-I in the blood. Levels of IGF-1 and GH change throughout your life. They: Are normally low when you are a child; Increase until they peak during puberty; Decrease once you are an adult; Besides growth, GH also helps control your metabolism (the process your body uses to make energy from the food you eat).

Some conditions, such as pituitary tumors, can cause your body to make too much or too little GH.

Why this test is done

Your health care provider may order an IGF-1 test if you or your child has symptoms of a GH disorder or to monitor treatment for a GH disorder.

Symptoms of GH deficiency or GH insensitivity in children include:

• Slowed growth rate compared with children of the same age
• Shorter height, arms, and legs, and lower weight than children of the same age
• Small penis in males
• Thin hair
• Poor nail growth

Adults with GH deficiency may have symptoms such as fatigue and decreased bone density and muscle mass. But IGF-1 testing isn't common for adults, as other disorders are much more likely to cause these symptoms.

Symptoms of GH excess (gigantism) in children include:

• Excessive growth compared with children of the same age
• Overly large head
• Larger than normal hands and feet
• Mild to moderate obesity

Symptoms of GH excess (acromegaly) in adults include:

• Deep, husky voice
• Larger than normal facial features such as lips, nose, and tongue
• Excessive sweating and body odor
• Thickening of bones
• Coarse, oily skin
• Irregular menstrual cycles in women
• Erectile dysfunction in men

How to prepare

You don't need any special preparations for an IGF-1 test.

Sample type

Blood

Other names for this test

somatomedin C test