Understanding growth hormone

Growth hormone (GH) is secreted by pituitary cells called Somatotrophs. The secretion of GH, like a few others, follows a day-night rhythm. GH levels are highest at night-time when we are asleep, and relatively lower during the day. GH secretion varies at different stages of life. Adolescents have the highest levels, followed by children, and then adults. As we age, the GH levels decrease. GH is ketogenic, i.e., it stimulates the formation of free fatty acids, which can be used by the body as a fuel when it is deprived of glucose.

As the name indicates, the main function of growth hormone in children and adolescents is regulation of growth. GH does this by recruiting other hormones, mainly IGF-1 (Insulin-like Growth Factor-1), which is secreted by the liver in response to GH. There are many others in the family, but IGF-1 is by far the most important.