Growth Hormone (GH) is similar in structure to the hormone Prolactin and has some degree of overlapping biological effects. GH is the most abundant hormone produced in the adenohypophysis by somatotropic cells, and is stored within the intracellular granules of these acidophilic cells.
The plasma concentration of GH is known to fluctuate widely throughout the day, with fairly steady and low levels during morning and daytime hours with brief spikes occurring 2-3 hours after meals and exercise. During nighttime hours, GH levels are markedly increased over morning levels, with concentrations of secretory activity rising after 90 minutes of sleep, and reaching peak levels during the period of deepest sleep, which facilitates skeletal growth, regeneration, and healing.
