IGF stands for Insulin-like Growth Factor-1 and it helps to promote the normal growth of bone and tissues. The test is ordered to evaluate the levels of IGF-1 in the blood. The IGF-1 works with growth hormone (GH) and it tracks GH excesses and deficiencies throughout the day. This helps to keep track of GH levels and is often used to evaluate GH excess or GH deficiency. The IGF-1-Somatomedin C test may also be ordered with other pituitary hormone tests such as prolactin or FSH and LH used to diagnose the dysfunction in pituitary glands. This test is broadly used to keep track of the GH factor as it becomes unstable throughout the day.