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 peptide hormones which are small proteins made up of a small chain of amino acids. IGF-1 and GH are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland which sits at base of the brain behind the bridge of your…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 peptide hormones which are small proteins made up of a small chain of amino acids. IGF-1 and GH are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland which sits at 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 in response to GH stimulation and mainly comes from the liver with a little from muscles. It mediates many of the actions of GH, stimulating the growth of bones and other tissues and increasing the production of muscle mass. IGF-1 excesses and deficiencies mirrors those of GH, but its level does not fluctuate during the day as does GH which makes 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 tumour 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 as a consequence of conditions such as malnutrition and chronic diseases. 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. 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 cardiovascular disease risk, 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 tumour (usually benign). Frequently, the tumour 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 collected by inserting a needle into a vein in your 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. See MoreSee Less
