Good Read for you.....
Growth hormone can be given either substaneously or by intra-muscular injection with equal therapeutic activity. Subcutaneous administration is now used almost exclusively because intra-muscular administration is fraught with an increase in side effects without any additional therapeutic benefit. The reason for this has to do with the biofeedback mechanism for growth hormone. Most of our natural pituitary growth hormone secretion occurs at night during deep stages of sleep. Injecting growth hormone at night raises the serum level of growth hormone precisely during the time the pituitary is scheduled to become active. This high serum level of growth hormone from the injection can suppress our natural pituitary function by negative feedback. We then not only lose the benefit of our own endogenous growth hormone, but also run the risk of surpressing the pituitary, thus making it "lazy". For the most part, the pituitary has completed its function and is at rest by 5 a.m. Therefore injecting after awakening in the morning results in injecting "on top of the peak" of endogenous (our own) growth hormone, so as not to suppress the pituitary. By the time the pituitary is ready again for its nighttime activity, the growth hormone given in the morning injection has been completely metabolized. This eliminates the risk of pituitary suppression.