The growth hormones is a polypeptide hormone consisting of 191 amino acids. In humans it is produced in the hypophysis and released if there are the right stimuli (e.g. training, sleep, stress, low blood sugar level). It is now important to understand that the freed HGH (human growth hormones) itself has no direct effect but only stimulates the liver to produce and release insulin-like growth factors and somatomedins. These growth factors are then the ones that cause various effects on the body. The problem, however, is that the liver is only capable of producing a limited amount of these substances so that the effect is limited. If growth hormones are injected they only stimulate the liver to produce and release these substances and thus, as already mentione, have no direct effect.