Growth hormone release is initiated in the hypothalamus, which communicates with the pituitary gland.

“Remember, it all starts in the brain, in the hypothalamus. The hypothalamus is a brain area that controls things like sexual behavior, temperature regulation, circadian behavior, meaning when you want to be awake and when you want to be asleep, aggression, all of that. There are other brain areas involved too but it has a rich collection of different neurons involved in all these very basic functions. Now, as we talked about the releasing hormones, the growth hormone-releasing hormone, it comes from neurons in the hypothalamus. Those then communicate with the pituitary and the pituitary releases growth hormone and then the growth hormone acts on all these different tissues, muscle, liver, cartilage, et cetera, body fat.”