What is HGH?
Human growth hormone, also called somatotropin, is a chain of 191 amino acids that the pituitary gland releases in pulses. The largest pulses usually come soon after falling into deep sleep, and output tends to fall with age. Medical HGH was first extracted from human pituitary glands collected after death. In 1985 that supply was stopped in the US after it was linked to Creutzfeldt-Jakob disease, and recombinant HGH made by engineered cells replaced it.
Somatropin is used for children with growth hormone deficiency and several other growth disorders, such as Turner syndrome and Prader-Willi syndrome, and for adults with confirmed deficiency. At 191 amino acids, HGH is a protein hormone, far larger than a typical peptide. It sits in this library because many of the growth hormone peptides on Matthew's channel work by prompting the pituitary to release more of it.
How does HGH work?
HGH acts on receptors in the liver, muscle, fat, bone and other tissues. A major effect is telling the liver to make insulin-like growth factor 1 (IGF-1), which carries out much of its growth-promoting work. HGH also acts directly. It prompts fat cells to release stored fat, helps the body hold on to protein and works against insulin, which tends to raise blood sugar.
The body normally keeps HGH in check. The hypothalamus sends growth hormone-releasing hormone (GHRH) to switch release on and somatostatin to switch it off, ghrelin from the stomach adds another push, and rising IGF-1 signals the brain to slow down. Taking HGH bypasses this loop. That is the key difference from peptides such as sermorelin or ipamorelin, which prompt the pituitary to release its own hormone.
What has research looked at?
- Growth in children
- Decades of clinical use show that HGH increases growth rate and adult height in children with growth hormone deficiency and several other approved conditions. This is its best-established use.
- Adults with deficiency
- In adults with confirmed deficiency, replacement trials reported more lean mass, less abdominal fat and gradual gains in bone density, and some found better quality-of-life scores.
- Healthy older adults
- A small, widely cited 1990 study in older men reported more lean mass and less fat. Later reviews of trials in healthy older people found modest body composition changes without consistent gains in strength, and more side effects.
- Athletes and fit adults
- Studies in healthy, active adults found increases in lean mass, part of which may be water, with little consistent improvement in strength or endurance.
- Skin, sleep and recovery
- These are common claims, but direct research in people without deficiency is limited, so most of the support is borrowed from what HGH does in deficiency.
The evidence is strong for treating deficiency and much weaker for anti-aging or body composition in healthy adults. Those trials have been small and short, they mostly measured body composition rather than health or function, and long-term outcomes in healthy people are unknown.
Side effects and cautions
The side effects of HGH are well documented because it has been prescribed for decades. Many come from fluid retention and from its effect on blood sugar, and they are more common in older adults and when IGF-1 rises above the normal range. Long-term excess growth hormone, as in the condition acromegaly, can enlarge the hands, feet, jaw and organs. Anyone weighing a growth hormone medicine should talk to a qualified clinician.
- Fluid retention
- Swelling of the hands and feet, joint and muscle aches, tingling and carpal tunnel syndrome, when fluid presses on a nerve in the wrist, are among the most common effects.
- Blood sugar
- HGH works against insulin, so it can raise blood sugar and worsen insulin resistance, which matters for anyone with or at risk of diabetes.
- Cancer history
- Because HGH and IGF-1 promote cell growth, HGH is not used in people with active cancer, and a past history of cancer needs careful review.
- Critical illness and rare effects
- Large trials in critically ill adults found higher death rates with HGH. Rare effects include raised pressure inside the skull and, in children, hip and spine problems.
Further reading
This page summarizes the research in plain words. To read the studies yourself:
- Published studies on Human growth hormone PubMed, US National Library of Medicine
- Registered human trials of Human growth hormone ClinicalTrials.gov
