Sermorelin therapy results work best before symptoms of HGH decline appear. By the time you notice any signs of HGH deficiency, your human growth hormone levels have been on the downswing for many years, if not decades. The slow-acting nature of sermorelin will not provide the boost in HGH levels that you need, as fast as you need them. The better option if blood test results show a significant decline in growth hormone levels is to use HGH therapy to provide the body with immediate results.