Growth Hormone Blood Test Panel

This test measures the amount of growth hormone (GH) in the blood. GH is a hormone produced by the pituitary gland. Growth hormone is essential for a child's normal growth and development and promotes proper linear bone growth from birth through puberty. Children with insufficient GH production grow more slowly and are smaller in size for their age. Excess GH is most often due to a GH-secreting pituitary tumor (usually benign). Too much GH can cause children's long bones to continue to grow beyond puberty, resulting in gigantism with heights of 7 or more feet tall. Those with excess GH may also have thickening of facial features, general weakness, delayed puberty, and headaches. Gigantism is an extremely rare condition. Although GH is not as active in adults, it does play a role in regulating bone density, muscle mass, and lipid metabolism. Deficiencies can lead to decreased bone densities, less muscle mass, and altered lipid levels. Excess GH in adults can lead to acromegaly, marked not by bone lengthening but by bone thickening.

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 polypeptide hormones, small proteins that are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland located at the 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 by the liver and skeletal muscle as well as many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulating the growth of bones and other tissues and promoting the production of lean muscle mass. IGF-1 mirrors GH excesses and deficiencies, but its level is stable throughout the day, making it a useful indicator of average GH levels.

z Score. A z-score (aka, a standard score) indicates how many standard deviations an element is from the mean. A z-score can be calculated from the following formula. z = (X - µ) / s where z is the z-score, X is the value of the element, µ is the population mean, and s is the standard deviation.