Growth hormone (GH)
What it measures, and what changes the number.
Growth hormone is produced by the pituitary gland and influences growth, body composition and metabolism. This test measures the amount of growth hormone in a blood sample.
Because growth hormone largely acts by prompting the liver to make IGF-1, the two are usually read together; IGF-1 gives a steadier picture of overall growth hormone activity. Glucose is relevant because some formal assessments measure growth hormone after a glucose drink, and other pituitary hormones such as Prolactin are sometimes ordered on the same request.
Growth hormone is released in pulses, with bursts during sleep and after exercise, and it is affected by recent meals and stress. A single random sample can therefore vary a lot, which is why it is often measured under controlled conditions such as fasting or as part of a stimulation or suppression test. Different immunoassays can give different values. Labs may print it as Hormona de Crecimiento.