Insulin-Like Growth Factor-1, IGF-1, (Somatomedin-C) Test
Insulin-Like Growth Factor-1, IGF-1, (Somatomedin-C) Test
Insulin-like growth factor -1 (IGF-1) is a laboratory test that measures the amount of IGF-1 in the patient's blood sample. IGF-1, or somatomedin C, is a hormone structurally similar to insulin that plays a crucial role in tissue growth and the body's metabolism. IGF-1 is released by the liver in response to growth hormone (GH) secreted from the pituitary gland.
Because the release of GH in the blood is pulsatile depending on the activity levels and diet, it isn't always easy to interpret a single GH test result. However, unlike GH, IGF-1 is more stable and mirrors GH measurement and, therefore, is prescribed to diagnose many problems related to too much or too little GH.
What is the Insulin-Like Growth Factor-1 Test Used For?
Your doctor may use GH testing along with the IGF-1 test
To diagnose pituitary gland disorders
For diagnosing growth hormone disorders in children
To evaluate the lack of responsiveness to GH (aka Laron Syndrome)
As follow up to abnormal results on another hormone test
To monitor treatment effectiveness for a GH-producing pituitary tumor
To guage GH production at regular intervals and watch for recurrence of pituitary tumors
To monitor patient’s response to GH therapy
Symptoms of Growth Hormone Disorders
Symptoms of GH deficiency or insensitivity in children include
Slowed growth rate and short stature
Decreased bone density and muscle mass
Poor hair and nail growth
Difficulty with concentration or memory
Symptoms of GH excess (gigantism) in children include
Unusually tall stature
Overly large head with unusual facial features, especially jaw and forehead
Huge hands and feet
General weakness
Mild to moderate obesity
Adults with excess GH production(acromegaly) experience
Deep husky voice
Thickening of bone
Facial changes such as a protruding jaw or enlarged nose
Preparation for Test
Generally, the IGF-1 test requires no special preparation. But before blood sample collection, ask your doctor whether you should avoid eating or drinking ahead of time or stop taking any medicines or supplements. Make sure your doctor knows the history of your medical conditions and allergies.
Interpretation of Test Results
Results of IGF-1 are given in nanograms per milliliter (ng/mL) and are interpreted as follows:
Positive result (Abnormal)
This report suggests abnormal levels of IGF-1 in the blood, indicating higher or lower production of GH.
Having a lower-than-normal level of IGF-1 means that the body's growth and development processes aren't working as they should for several reasons, such as
- GH deficiency or insensitivity to GH caused by a genetic disorder or brain disease
- Nutritional deficiencies
- Hypopituitarism
- Uncontrolled diabetes mellitus
- Chronic kidney or liver diseases
- Low thyroid hormone levels
- High doses of estrogen
- Intake of medications like corticosteroids
Higher than normal levels of IGF-1 indicate problems related to the pituitary gland, often seen in gigantism in children or acromegaly in adults. Elevated IGF and GH may also be seen during pregnancy and puberty.
Negative result (Normal)
This report must be considered in context because some people can have normal IGF-1 levels with GH deficiency.
FAQs
How is the IGF-1 test done?
To do this test, your doctor will draw a blood sample from a vein in your arm using a needle.
What can affect my IGF-1 test results?
If you or your child are nutritionally deficient, it could affect your IGF-1 levels. Also, age matters because IGF-1 and GH tend to decline after puberty.
How long do my IGF-1 levels be monitored?
As long as you are considered to have abnormal (low or high) GH production or are receiving GH replacement therapy, your IGF-1 will require regular monitoring.
What is Laron Syndrome?
Laron syndrome is a rare genetic disorder where the body is incapable of responding to the growth hormone it produces, causing poor growth rate and short stature in children.
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