Test Details: 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. This test, along with the growth hormone (GH) test, is used to help diagnose growth hormone deficiency (GHD) or, less commonly, growth hormone excess; to evaluate pituitary function to monitor the effectiveness of GH treatment.