Human growth hormone (HGH) and its anabolic mediator called IGF-1 (insulin-like growth factor 1) can stimulate the growth of almost all tissues in the body.
This includes the growth and development of muscle tissue during childhood, as well as exerting potent muscle sparing effects in adulthood.
Due to the anabolic effects of the HGH for muscle tissue, it is widely promoted amongst the bodybuilding community as a drug that will help you pack on more muscle while shedding fat at the same time.
HGH is not a medication for muscle growth
Instead, the main population group which may benefit from the anabolic effects of HGH are people who are suffering from growth hormone deficiency (GHD) or other conditions that result in muscle wasting.
In fact, growth hormone has predominantly muscle sparing effects, which means that it can help increase muscle size mostly by reducing muscle breakdown in chronically ill patients, rather than accelerating muscle growth in healthy individuals.
How does HGH affect muscles?
Growth hormone can affect your muscles both directly and indirectly. Its direct effects are conveyed by stimulating the production of IGF-1 inside the tissue.
IGF-1 is the main mediator of the anabolic effects of the growth hormone. That’s why HGH stimulates IGF-1 production in almost all tissues, and your skeletal muscles are no exception.
Furthermore, HGH can affect muscles indirectly, by stimulating the production of IGF-1 in the liver. Then, the liver releases the mediator in your bloodstream and provides an additional anabolic stimulus to your tissues.
Researchers suggest that both circulating and locally produced IGF-1 affect muscle growth. The hormone does so by changing the balance between muscle protein synthesis and muscle protein breakdown. These processes occur constantly in your skeletal muscles, and the net result determines whether you will grow or lose muscle.
Via IGF-1, HGH appears to reduce protein breakdown and increase synthesis at the same time, which helps preserve a positive net balance and stimulates muscle growth.
Yet, studies suggest that HGH may stimulate growth mainly in people experiencing increased protein breakdown. This includes chronically ill patients such as those suffering from growth hormone deficiency (GHD).
In contrast, research is mostly mixed regarding the effects of GH on the muscle mass of healthy individuals.
Some small studies report decreased muscle protein breakdown without an increase in synthesis, while others suggest that there is no effect in healthy individuals after acute HGH administration.
When is HGH effective for muscles?
HGH therapy appears effective at increasing muscle mass in individuals who suffer from wasting due to different medical conditions.
Most notably, HGH replacement therapy can revert muscle loss in patients with GHD.
HGH therapy works by achieving normal serum growth hormone levels. This leads to an increase in the concentration of IGF-1 in muscle tissue, as well as to the restoration of optimal levels of circulating IGF-1.
Studies suggest that GH therapy increases IGF-1 levels within the first month, but it may take at least 2-3 months until there is a significant increase in muscle mass.
It’s important to note that the successful management of GHD related complaints such as muscle loss requires long-term HGH therapy. Discontinuing the treatment will likely cause the return of the symptoms.
HGH therapy is also FDA-approved for the management of muscle wasting due to AIDS. Yet, the therapy is usually applied for shorter periods of time and involves the use of supraphysiological doses.
For example, one study reports that 12-week HGH therapy in 178 HIV-infected patients with doses as high as 0.1 mg/kg daily can lead to a 3kg increase in lean body mass on average.
HGH therapy may also help reduce aging-related muscle loss, although the treatment has not been approved for this indication. The condition is also called sarcopenia and its exact causes remain unknown, although some scientists suggest it may be due to oxidative damage and death of satellite cells.
Yet, sarcopenia is a risk factor for increased morbidity and mortality amongst older individuals. Research suggests that HGH therapy may help revert the condition by reducing the age-related increase in oxidative stress that patients with sarcopenia experience.
Regardless of the medical indication, subcutaneous injections are the widely preferred method of injecting HGH compared to intramuscular administration.
This is because subcutaneous administration extends the half-life of the medication and prolongs its effectiveness after a single injection.
Furthermore, this helps better mimic the natural daily pulsatile secretion of GH by the pituitary gland.
Why is HGH used for bodybuilding?
HGH has been used for bodybuilding since the 80s when the purported benefits of HGH for physical performance were first published.
Following the initial research, there were new studies suggesting that the physical benefits of the therapy in healthy people may not be as significant as the scientists thought.
But nevertheless, the hormone has become one of the most commonly abused substances amongst athletes and bodybuilders and the illegal practice continues to this day.
Currently, HGH injections are prescription medications and the FDA has approved the therapy for specific indications only. Thus, HGH therapy is not recommended for healthy people and taking the medication without having a prescription is illegal.
Apart from being a prescription only drug, WADA banned HGH, so it is not legally available for bodybuilding or other professional sports.
Most bodybuilders who start HGH cycle are expecting an improved physique including increased muscle growth, as well as reduced subcutaneous body fat. Some bodybuilders also take the medication in an attempt to recover from training injuries.
Yet, most trials in athletes including bodybuilders and weight lifters do not report any noticeable benefits of HGH injections for body composition when compared to placebo.
Furthermore, the researchers did not find any benefits in terms of physical performance, strength or endurance.
Nevertheless, both professional and amateur bodybuilders around the world continue taking HGH injections in an attempt to gain an edge over the competition or to simply improve their physique.
Similarly to the recommendations given to GHD patients, bodybuilders inject HGH subcutaneously, usually before bed. Yet, the dosage is considerably higher.
Normally, GHD patients take between 0.2-1 mg HGH daily, while bodybuilders typically take anywhere between 3-8 mg per day, 3-4 days per week in cycles of four to six weeks.
What are the side effects of using HGH for bodybuilding?
HGH is safe and effective therapy for GHD, as long as you are under medical supervision and your doctor is regulating your dosage to help you avoid any side effects
Yet, bodybuilders use much higher doses of HGH and often lack any medical supervision while doing so. The result is an increased risk of side effects such as water retention and insulin resistance.
Water retention can lead to joint and muscle pains, carpal tunnel syndrome, headache, etc.
Besides, HGH will not provide all the benefits you may expect if your growth hormone levels are already normal. Only individuals with GHD may expect improved strength, endurance, sleep, mood, energy levels, as these effects will appear as a result of managing their symptoms.
Those without GHD may experience only a slight increase in lean body mass and body fat reduction. What is more, the increase in lean body mass may be due to water retention rather than muscle mass gains.