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IGF-1
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<!-- ------------------------------ * Overview type analyte page * ------------------------------ -->Also known as: Somatomedin C
Formal name: Insulin-like Growth Factor - 1
<!-- medical codes (currently not displayed on web site) --><!-- tab navigation --><!-- tab content --><!-- At a Glace -------------------------------------------------------------->At a Glance
Why Get Tested?
To identify diseases and conditions caused by deficiencies and overproduction of growth hormone (GH), to evaluate pituitary function, and to monitor the effectiveness of GH treatment
When to Get Tested?
When you have symptoms of slow growth, short stature, and delayed development (in children) or decreased bone density, reduced muscle strength, and increased lipids (in adults) that suggest insufficient GH and IGF-1 production; when you have symptoms of gigantism (in children) or acromegaly (in adults) that suggest excess GH and IGF-1 production; during and after treatment for GH abnormalities; as part of an evaluation of pituitary function
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
Generally none, unless instructed to fast
<!-- Test Sample -------------------------------------------------------------->The Test Sample
What is being tested?
The insulin-like growth factor-1 (IGF-1) test is an indirect measure of the average amount of growth hormone (GH) being produced by the body. IGF-1 and GH are polypeptide hormones, small proteins that are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland located at the base of the brain behind the bridge of your nose. GH is secreted into the bloodstream in pulses throughout the day and night with peaks that occur mostly during the night. IGF-1 is produced by the liver and skeletal muscle as well as many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulating the growth of bones and other tissues and promoting the production of lean muscle mass. IGF-1 mirrors GH excesses and deficiencies, but its level is stable throughout the day, making it a useful indicator of average GH levels.
Like GH, IGF-1 levels are normally low in early childhood, increase gradually during childhood, peak during puberty, and then decline in adult life. Deficiencies in GH and IGF-1 may be caused by conditions such as hypopituitarism or by the presence of a non-GH-producing pituitary tumor that damages hormone-producing cells. Deficiencies in IGF-1 also occur where there is a lack of responsiveness to GH. This insensitivity may be primary (genetic) or secondary to conditions such as malnutrition, hypothyroidism, sex hormone deficiency, and chronic diseases. Genetic GH insensitivity (GH resistance) is very rare.
Deficiencies early in life can inhibit bone growth and overall development and can result in a child with a shorter than normal stature. In adults, decreased production can lead to low bone densities, less muscle mass, and altered lipids. However, testing for GH deficiency or IGF-1 deficiency is not routine in adults who have decreased bone density and/or muscle strength, or increased lipids. GH deficiency and consequent IGF-1 deficiency is only a very rare cause of these disorders.
Excess GH and IGF-1 can cause abnormal growth of the skeleton and other signs and symptoms characteristic of gigantism and acromegaly. In children, gigantism causes bones to grow longer, resulting in a very tall person with large feet and hands. In adults, acromegaly causes bones to thicken and soft tissues, such as the nose, to swell. Both conditions can lead to enlarged organs, such as the heart, and to other complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, and a decreased life span. The most common reason for the pituitary to secrete excessive amounts of GH is a GH-producing pituitary tumor (usually benign). Frequently, the tumor can be surgically removed and/or treated with drugs or radiation. In most cases, this will cause GH and IGF-1 levels to return to normal or near normal levels.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
In general, no test preparation is needed; however, since this test may be performed at the same time as others, fasting for at least 12 hours may be required.
<!-- The Test -------------------------------------------------------------->
The Test
How is it used?
IGF-1 is measured to help diagnose the cause of growth abnormalities, evaluate pituitary function, and monitor treatment of GH deficiencies and excesses. It is not diagnostic of a GH deficiency but may be ordered along with GH stimulation tests to offer additional information. IGF-1 levels and the measurement of GH can also provide information related to GH insensitivity. Prior to performing definitive GH testing, if the IGF-1 level is found to be normal for age and sex, GH deficiency is excluded and definitive testing is not necessary.
IGF-1 may be ordered with other pituitary hormone tests, such as adrenocorticotropic hormone (ACTH), to help diagnose hypopituitarism. It may be used to monitor the effectiveness of treatment for growth hormone deficiencies and growth hormone insensitivity. However, IGF-1 is not routinely measured to monitor GH treatment of GH-deficient children. The best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their height velocity and their absolute height.
IGF-1 testing and a GH suppression test can be used to detect a GH-producing pituitary tumor. An anterior pituitary tumor is then confirmed with imaging scans that help identify and locate the tumor. If surgery is necessary, GH and IGF-1 levels are measured after the tumor's removal to determine whether all of the tumor was successfully removed. Drug and/or radiation therapy may be used in addition to, or sometimes instead of, surgery to try to decrease GH production and return IGF-1 to a normal or near normal concentration. IGF-1 may be ordered to monitor the effectiveness of this therapy at regular intervals for years afterward to monitor GH production and to detect tumor recurrence.
When is it ordered?
IGF-1 testing may be ordered, along with a GH stimulation test, when a child has symptoms of GH deficiency, such as a slowed growth rate and short stature. They also may be ordered when adults have symptoms that the doctor suspects may be due to a GH deficiency, such as decreased bone density, fatigue, adverse lipid changes, and reduced exercise tolerance. However, testing for IGF-1 deficiency is not routine in adults who have these symptoms; GH and IGF-1 deficiency are only very rare causes of these disorders.
An IGF-1 also may be ordered when a doctor suspects that someone has an underactive pituitary gland and at intervals to monitor those on GH therapy. However, IGF-1 is not routinely measured to monitor GH treatment of GH-deficient children. Again, the best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their height velocity and their absolute height.
IGF-1 testing may be ordered, along with a GH suppression test, when a child has symptoms of gigantism or when an adult shows signs of acromegaly.
When a GH-producing pituitary tumor is found, GH and IGF-1 are ordered after the tumor is surgically removed to determine whether all of the tumor has been extracted. IGF-1 also is ordered at regular intervals when someone is undergoing the drug and/or radiation therapy that frequently follow tumor surgery.
IGF-1 levels may be ordered at regular intervals for many years to monitor a person's GH production and to watch for pituitary tumor recurrence.
What does the test result mean?
A normal concentration of IGF-1 must be considered in context. Some people can have a GH deficiency and still have a normal IGF-1 concentration.
Decreased IGF-1
If the IGF-1 concentration is decreased, then it is likely that there is a GH deficiency or an insensitivity to GH. If this is in a child, the GH deficiency may have already caused short stature and delayed development and may be treated with GH supplementation. Adults will have an age-related decrease in production, but lower than expected concentrations may reflect a GH deficiency or insensitivity.
If a decrease in IGF-1 is due to a more general decrease in pituitary function (hypopituitarism), then several of the person's pituitary hormones will need to be evaluated and may be supplemented to bring them up to normal levels. Reduced pituitary function may be due to inherited defects or can develop as a result of pituitary damage following conditions such as trauma, infections, and inflammation.
Decreased levels of IGF-1 also may be seen with nutritional deficiencies (including anorexia nervosa), chronic kidney or liver disease, inactive/ineffective forms of GH, and with high doses of estrogen.
Increased IGF-1
Elevated levels of IGF-1 usually indicate an increased production of GH. Since GH levels vary throughout the day, IGF-1 concentrations are a reflection of average GH production, not of the actual amount of GH in the blood at the time that the sample for the IGF-1 measurement was taken. This is accurate up to the point at which the liver's capacity to produce IGF-1 is reached. With severely increased GH production, the IGF-1 level will stabilize at an elevated maximum concentration.
Increased concentrations of GH and IGF-1 are normal during puberty and pregnancy but otherwise are most frequently due to pituitary tumors (usually benign).
If IGF-1 is still elevated after the surgical removal of a pituitary tumor, then the surgery may not have been fully effective. Decreasing IGF-1 concentrations during subsequent drug and/or radiation therapies indicate that the treatment is lowering GH production. If levels of IGF-1 become "normalized," then the person is no longer producing excess amounts of GH. When someone is undergoing long-term monitoring, an increase in IGF-1 levels may indicate a recurrence of the pituitary tumor.
Is there anything else I should know?
If an IGF-1 level is normal and the doctor still strongly suspects a GH deficiency, then the doctor may order another test, an IGFBP-3 (insulin-like growth factor binding protein 3), to help confirm the GH deficiency. Almost all IGF-1 in the blood is bound to binding proteins, with IGFBP-3 being the most prevalent form.
<!-- Share this page -->
<!-- ------------------------------ * Overview type analyte page * ------------------------------ -->Also known as: Somatomedin C
Formal name: Insulin-like Growth Factor - 1
<!-- medical codes (currently not displayed on web site) --><!-- tab navigation --><!-- tab content --><!-- At a Glace -------------------------------------------------------------->At a Glance
Why Get Tested?
To identify diseases and conditions caused by deficiencies and overproduction of growth hormone (GH), to evaluate pituitary function, and to monitor the effectiveness of GH treatment
When to Get Tested?
When you have symptoms of slow growth, short stature, and delayed development (in children) or decreased bone density, reduced muscle strength, and increased lipids (in adults) that suggest insufficient GH and IGF-1 production; when you have symptoms of gigantism (in children) or acromegaly (in adults) that suggest excess GH and IGF-1 production; during and after treatment for GH abnormalities; as part of an evaluation of pituitary function
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
Generally none, unless instructed to fast
<!-- Test Sample -------------------------------------------------------------->The Test Sample
What is being tested?
The insulin-like growth factor-1 (IGF-1) test is an indirect measure of the average amount of growth hormone (GH) being produced by the body. IGF-1 and GH are polypeptide hormones, small proteins that are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland located at the base of the brain behind the bridge of your nose. GH is secreted into the bloodstream in pulses throughout the day and night with peaks that occur mostly during the night. IGF-1 is produced by the liver and skeletal muscle as well as many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulating the growth of bones and other tissues and promoting the production of lean muscle mass. IGF-1 mirrors GH excesses and deficiencies, but its level is stable throughout the day, making it a useful indicator of average GH levels.
Like GH, IGF-1 levels are normally low in early childhood, increase gradually during childhood, peak during puberty, and then decline in adult life. Deficiencies in GH and IGF-1 may be caused by conditions such as hypopituitarism or by the presence of a non-GH-producing pituitary tumor that damages hormone-producing cells. Deficiencies in IGF-1 also occur where there is a lack of responsiveness to GH. This insensitivity may be primary (genetic) or secondary to conditions such as malnutrition, hypothyroidism, sex hormone deficiency, and chronic diseases. Genetic GH insensitivity (GH resistance) is very rare.
Deficiencies early in life can inhibit bone growth and overall development and can result in a child with a shorter than normal stature. In adults, decreased production can lead to low bone densities, less muscle mass, and altered lipids. However, testing for GH deficiency or IGF-1 deficiency is not routine in adults who have decreased bone density and/or muscle strength, or increased lipids. GH deficiency and consequent IGF-1 deficiency is only a very rare cause of these disorders.
Excess GH and IGF-1 can cause abnormal growth of the skeleton and other signs and symptoms characteristic of gigantism and acromegaly. In children, gigantism causes bones to grow longer, resulting in a very tall person with large feet and hands. In adults, acromegaly causes bones to thicken and soft tissues, such as the nose, to swell. Both conditions can lead to enlarged organs, such as the heart, and to other complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, and a decreased life span. The most common reason for the pituitary to secrete excessive amounts of GH is a GH-producing pituitary tumor (usually benign). Frequently, the tumor can be surgically removed and/or treated with drugs or radiation. In most cases, this will cause GH and IGF-1 levels to return to normal or near normal levels.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
In general, no test preparation is needed; however, since this test may be performed at the same time as others, fasting for at least 12 hours may be required.
<!-- The Test -------------------------------------------------------------->
The Test
How is it used?
IGF-1 is measured to help diagnose the cause of growth abnormalities, evaluate pituitary function, and monitor treatment of GH deficiencies and excesses. It is not diagnostic of a GH deficiency but may be ordered along with GH stimulation tests to offer additional information. IGF-1 levels and the measurement of GH can also provide information related to GH insensitivity. Prior to performing definitive GH testing, if the IGF-1 level is found to be normal for age and sex, GH deficiency is excluded and definitive testing is not necessary.
IGF-1 may be ordered with other pituitary hormone tests, such as adrenocorticotropic hormone (ACTH), to help diagnose hypopituitarism. It may be used to monitor the effectiveness of treatment for growth hormone deficiencies and growth hormone insensitivity. However, IGF-1 is not routinely measured to monitor GH treatment of GH-deficient children. The best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their height velocity and their absolute height.
IGF-1 testing and a GH suppression test can be used to detect a GH-producing pituitary tumor. An anterior pituitary tumor is then confirmed with imaging scans that help identify and locate the tumor. If surgery is necessary, GH and IGF-1 levels are measured after the tumor's removal to determine whether all of the tumor was successfully removed. Drug and/or radiation therapy may be used in addition to, or sometimes instead of, surgery to try to decrease GH production and return IGF-1 to a normal or near normal concentration. IGF-1 may be ordered to monitor the effectiveness of this therapy at regular intervals for years afterward to monitor GH production and to detect tumor recurrence.
When is it ordered?
IGF-1 testing may be ordered, along with a GH stimulation test, when a child has symptoms of GH deficiency, such as a slowed growth rate and short stature. They also may be ordered when adults have symptoms that the doctor suspects may be due to a GH deficiency, such as decreased bone density, fatigue, adverse lipid changes, and reduced exercise tolerance. However, testing for IGF-1 deficiency is not routine in adults who have these symptoms; GH and IGF-1 deficiency are only very rare causes of these disorders.
An IGF-1 also may be ordered when a doctor suspects that someone has an underactive pituitary gland and at intervals to monitor those on GH therapy. However, IGF-1 is not routinely measured to monitor GH treatment of GH-deficient children. Again, the best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their height velocity and their absolute height.
IGF-1 testing may be ordered, along with a GH suppression test, when a child has symptoms of gigantism or when an adult shows signs of acromegaly.
When a GH-producing pituitary tumor is found, GH and IGF-1 are ordered after the tumor is surgically removed to determine whether all of the tumor has been extracted. IGF-1 also is ordered at regular intervals when someone is undergoing the drug and/or radiation therapy that frequently follow tumor surgery.
IGF-1 levels may be ordered at regular intervals for many years to monitor a person's GH production and to watch for pituitary tumor recurrence.
What does the test result mean?
A normal concentration of IGF-1 must be considered in context. Some people can have a GH deficiency and still have a normal IGF-1 concentration.
Decreased IGF-1
If the IGF-1 concentration is decreased, then it is likely that there is a GH deficiency or an insensitivity to GH. If this is in a child, the GH deficiency may have already caused short stature and delayed development and may be treated with GH supplementation. Adults will have an age-related decrease in production, but lower than expected concentrations may reflect a GH deficiency or insensitivity.
If a decrease in IGF-1 is due to a more general decrease in pituitary function (hypopituitarism), then several of the person's pituitary hormones will need to be evaluated and may be supplemented to bring them up to normal levels. Reduced pituitary function may be due to inherited defects or can develop as a result of pituitary damage following conditions such as trauma, infections, and inflammation.
Decreased levels of IGF-1 also may be seen with nutritional deficiencies (including anorexia nervosa), chronic kidney or liver disease, inactive/ineffective forms of GH, and with high doses of estrogen.
Increased IGF-1
Elevated levels of IGF-1 usually indicate an increased production of GH. Since GH levels vary throughout the day, IGF-1 concentrations are a reflection of average GH production, not of the actual amount of GH in the blood at the time that the sample for the IGF-1 measurement was taken. This is accurate up to the point at which the liver's capacity to produce IGF-1 is reached. With severely increased GH production, the IGF-1 level will stabilize at an elevated maximum concentration.
Increased concentrations of GH and IGF-1 are normal during puberty and pregnancy but otherwise are most frequently due to pituitary tumors (usually benign).
If IGF-1 is still elevated after the surgical removal of a pituitary tumor, then the surgery may not have been fully effective. Decreasing IGF-1 concentrations during subsequent drug and/or radiation therapies indicate that the treatment is lowering GH production. If levels of IGF-1 become "normalized," then the person is no longer producing excess amounts of GH. When someone is undergoing long-term monitoring, an increase in IGF-1 levels may indicate a recurrence of the pituitary tumor.
Is there anything else I should know?
If an IGF-1 level is normal and the doctor still strongly suspects a GH deficiency, then the doctor may order another test, an IGFBP-3 (insulin-like growth factor binding protein 3), to help confirm the GH deficiency. Almost all IGF-1 in the blood is bound to binding proteins, with IGFBP-3 being the most prevalent form.
