Growth hormone is a protein hormone manufactured in the pituitary, a small gland located at the base of the brain behind the bridge of the nose. This hormone is secreted in a “pulsatile” (burst-like or episodic) manner over the course of the day, with greater secretion at night. GH is essential for a child’s bone growth and normal development. In adults, GH helps control energy production from food (metabolism). It helps synthesize lipids (fats), protein and glucose. Results are expressed in µg/L (micrograms of growth hormone per litre of blood).
Because of the pulsatile secretion, the measurement of isolated levels of growth hormone is usually of little clinical usefulness, and stimulation/suppression tests are required to make a proper diagnosis. Measuring IGF-1 levels is more useful than measuring levels of GH to diagnose a growth hormone deficiency or excess.