Peptides simply are short chains of amino acids linked together. There might be 2 or 3 or more amino acids. When the number of amino acids in the chain reaches around ten or so, the result would be a substance called polypeptides. Those polypeptides usually have molecular weights of a few thousand, while proteins have molecular weights of tens of thousands.
Peptides are usually used by athletes because they help the muscles and soft tissues in the rebuilding healing process. In bodybuilding muscle mass can be built quickly because the healing process noticeably increased and so the end effect is increased muscle mass and reduced body fat in a shorter timeframe.
There are several kinds of peptides used for different purposes. Such as increasing natural growth hormone release and promoting joints and soft tissue healing process and so on.
The most important and widely used peptide of all is human growth hormone or HGH. HGH is not an anabolic steroid like some might think due to its use in the bodybuilding world alongside anabolic steroids. Human Growth Hormone is what is referred to as a protein hormone (or a peptide hormone). It is naturally secreted at the pituitary gland. The production system can be simply described like the following, the hypothalamus release a hormone known as GHRH (Growth Hormone Releasing Hormone, AKA Somatocrinin) and another hormone known as GHIH (Growth Hormone Inhibiting Hormone) into the pituitary gland, which in turn manufactures and produces and discharges its Human Growth Hormone storage into the bloodstream.  Human Growth Hormone is a very close relative to the hormone Prolactin, which also belongs to the Somatotropin family of hormones.
The use of HGH in general, is safe and well-tolerated in reasonable dosages and it definitely doesnt come with the side-effects of anabolic steroids. Having said that though, there some specific side effects linked to dosing HGH which we will touch on a bit later in this article.
So again HGH is a peptide hormone produced by the pituitary and has multiple characteristics and functions in the human body. It works on multiple tissues of the body via the GH receptor. The activated GH receptor provides some effects directly and other effects indirectly by stimulating the production of another hormone called Insulin-like growth factor or IGF1.
One note of extreme importance when using HGH which is that any injectable HGH preparation must be identical to natural HGH, which contains 191 amino acids in its structure. Some cheaper preparations, however, are false analog and contains 192 amino acids. These preparations and products can cause a dire immune response and should be avoided.
 The common desired effect of HGH use is the potential to increase muscular size, increase metabolism, reduce fat storage in the body, reduce elevated blood pressure, and improve healing and strength, increase natural Testosterone production, improved sleep, and a sense of well being. As well as for the purposes of anti-aging in regards to improvement of skin and hair appearance,
In muscles which is obviously the main reason in the bodybuilding world, HGH at supraphysiological doses interferes with insulin signaling, and decreases glucose uptake, increases fatty acid uptake, and increases the basal rate of lipid oxidation or fat burning.
In adipose tissue or fat cells, HGH increases lipolysis (burning of fat), decreases lipogenesis (accumulation of fat), decreases glucose uptake, and decreases the local activity of corticosteroids.
All the above-mentioned facts are what responsible for the fat loss effect and partitioning nutrients towards muscle instead of fat cells. Additionally, the increase in serum-free fatty acids produced from increased lipolysis appears to be GHs mechanism for its anabolic effect in muscles.
As for dosing, HGH dosages vary depending on the goal and the individual. 4iu per day seems to be the gold standard by which most users abide. However, many people need to bring that dose to a maximum of 2 IU per day to avoid side effects. Besides, this does seem to be the best for the life-enhancing effect in terms of skin and body composition.
When choosing to use 4 IU per day or higher as seen in some cases in professional bodybuilding, it becomes highly recommended to divide the dose into at least two doses per day or even more than two doses for better tolerance and fewer side effects.
Other main HGH faculty in the human body is the promotion of growth of bones, as well as muscle and internal organs growth, in addition to the healing/growth/repair of soft connective tissue such as tendons, ligaments, and joints. As for its influence on metabolism, it boosts the efficient functions of protein, carbohydrate, fat, and vitamin/mineral uptake.
Medically it is usually utilized in the treatment of many different types of disorders and ailments. Treatment of pituitary deficient dwarfism is one of the main conditions. As well as the treatment of AIDS/HIV related muscle wasting (or as a result of many other diseases).
HGH has Two main effects on muscles, induce hypertrophy which is the increase of the size of muscle cells, and hyperplasia, which in contrast the increase of the number of muscle cells. The interesting fact about Human Growth Hormone is its ability to generate a far greater amount of hyperplasia over hypertrophy which makes its use much more favorable to some athletes in specific sports than others.
When it comes to HGH side effects, human Growth Hormone tends to deplete potassium, phosphorous, and sodium levels, which the user should keep in mind and supplement with these minerals especially with higher doses. Human Growth Hormone has the side effect of decreasing the functions of and levels of T3 (Thyroid Hormone) in the body, which can temporarily disrupt metabolism. Once again, this is a dose-dependent effect.
Other side effects include joint pain which is One of the most common issues. This might sound like a paradox because of the fact that HGH helps with joint pain and the rebuilding of tendons. The truth is in order to create new joint tissue, the joints have to expand and be placed in a position which is something HGH certainly facilitates, but because there is new tissue growth, the HGH will result in temporary pain that might be frustrating but it is certainly not permanent. As that new tissue grows and calcifies, the pain will subside.
Water retention is another side effect of HGH. its not uncommon to see a lot of bloating and swelling in joint areas but this once again dosage-dependent. And there is the infamous Carpal Tunnel Syndrome or CTS which is usually associated with HGH use especially in high doses and/or at the beginning of use. CTS is common as a result of water retention. A simple explanation is that excess fluids will often press up against joints and cause numbness and pain to show up in those precise areas, in this case, the wrist.
Organ and tissue growth is yet another side effect of using HGH which might sound interesting, while the fact is that its one of the primary downfalls of HGH use because it can cause some permanent damage in the body. One thing must be mentioned in this regard is that this side effect is very much dose and length of use dependant and therefore proper and reasonable administration plan must be followed.
Other means of increasing natural HGH when the user wishes not to inject HGH is the use of certain peptides, such as Growth hormone stimulating peptide GHRPs such as GHRP-2, GHRP-6, Hexarelin, Ipamorelin; or administration of GHRHs such as Mod GRF 1-29 or CJC-1295.