What is IGF-1 ( INSULIN LIKE GROWTH FACTOR-1) SOMATOMEDIN-C ?
Insulin-like growth factor-1 (IGF-1) is a hormone that, along with growth hormone (GH), helps promote normal bone and tissue growth and development. The test measures the amount of IGF-1 in the blood.
IGF-1 is primarily produced in the liver, skeletal muscles, and many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulates the growth of bones and other tissues, and promotes the production of lean muscle mass. IGF-1 also plays a role in non-growth activities, such as glucose and lipid metabolism, and has been implicated in metabolic syndrome.
Since GH is released into the blood in pulses throughout the day, it is difficult to interpret the results from a single GH test. IGF-1 mirrors GH excesses and deficiencies, but unlike GH, its level is stable throughout the day. This makes IGF-1 a useful indicator of average GH levels. The IGF-1 test is therefore often used to help evaluate for GH deficiency or GH excess.
IGF-1 and Growth Deficiency
IGF-1 levels, like GH, are normally low in infancy, increase gradually during childhood, peak during puberty, and then decline in adult life. Deficiencies in GH and IGF-1 may be caused by:
- A dysfunctional pituitary gland with decreased pituitary hormones (hypopituitarism)
- A non-GH-producing pituitary tumor that damages cells that produce hormones
- A lack of responsiveness to GH. This insensitivity may be primary (genetic) or secondary to conditions such as malnutrition, hypothyroidism, sex hormone deficiency, kidney disease, liver disease, and congenital syndromes. Genetic GH insensitivity (GH resistance) is very rare, with about 300 cases reported worldwide.
IGF-1 deficiencies can inhibit bone growth and overall growth development, resulting in a child with a shorter than normal stature. In adults, decreased production can lead to low bone density, less muscle mass, and altered lipid levels. However, testing for IGF-1 deficiency or GH deficiency is not routinely done in adults who have decreased bone density and/or muscle strength or increased lipids. GH deficiency and consequently IGF-1 deficiency is a very rare cause of these disorders.
IGF-1 and Growth Hormone Excess
Excess GH and IGF-1 can cause abnormal growth of the skeleton and other signs and symptoms characteristic of two rare conditions, gigantism and acromegaly, generally due to a pituitary adenoma, a slow-growing, often benign tumor. This causes the pituitary to release excess amounts of GH. 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.
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 tissues to soften, as seen with the swelling of the nose. In contrast to giantism, adults with acromegaly do not grow tall. Both conditions can lead to enlarged organs (heart, liver, kidneys, spleen, thyroid/parathyroid glands, pancreas) and other complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, mild increase in cancer (breast, colon, prostate, lung), and a decreased lifespan.