IGF-1
What it measures, and what changes the number.
IGF-1, insulin-like growth factor 1, also called somatomedin C, is a hormone made mainly by the liver in response to growth hormone. It carries out many of growth hormone's effects on growth and metabolism, and this test measures its level in blood.
It is usually read alongside Growth hormone (GH). Because growth hormone is released in pulses, IGF-1 is often used as a steadier indicator of overall growth hormone activity. Glucose and Insulin are sometimes reviewed with it because of their links to growth hormone and metabolism.
IGF-1 stays fairly stable through the day, so timing matters less than for growth hormone. Most IGF-1 circulates bound to carrier proteins, and methods differ in how they remove them, so immunoassays and mass spectrometry (LC/MS) can give different results. Values are strongly age dependent. Labs may print it as IGF 1, LC/MS or Somatomedina C (IGF-1).
Often read alongside: Growth hormone (GH), Glucose, Insulin