Human Growth Hormone (HGH): What is it, Levels, and More – Verywell Health

Human growth hormone (HGH), also known as somatotropin, is a naturally occurring peptide hormone secreted by the pituitary gland. As its name implies, scientists originally found HGH to be responsible for growth regulation during childhood.

Research has since determined that it is responsible for many other functions such as regulating sugar and fat metabolism, bone growth, and cellular regeneration. Some research even suggests that it may play a role in how the heart functions.

Human growth hormone consists of a single chain of 191 amino acids. It is made in the brain but secreted in the bloodstream.

Its production is controlled by a complex set of hormones, mainly growth hormone-releasing hormone (GHRH) produced in the hypothalamus, somatostatin that is produced in various tissues throughout the body, and ghrelin, which is produced in the gastrointestinal tract.

The pituitary puts out HGH in pulsatile bursts that vary hourly. Higher daily hGH levels are seen after exercise, trauma, and sleep. Peak highest levels are reached at night. In general, HGH levels are increased in childhood, spike to their highest levels during puberty, and subsequently decrease as one ages.

HGH is mainly involved in two processesgrowth and metabolism.HGH stimulates bone and cartilage growth, especially during periods of rapid growth during childhood.

Cartilage-forming and bone-forming cells called chondrocytes and osteoblasts receive signals to increase replication and thus allow for growth in size via HGHs activation of the mitogen-activated protein (MAP) kinases designated ERKs (extracellular signal-regulated kinases) 1 and 2 cellular signaling pathways.

Activation of this phosphorylation intracellular signaling cascade results in a cascade of protein activation, which leads to increased gene transcription of the affected cells and ultimately causes increased gene replication and cellular growth.

Simultaneously, HGH upregulates insulin-like growth factor 1, which causes cells to increase amino acid uptake, protein synthesis, and decrease catabolism of proteins. This is the anabolic state.

HGH also mitigates insulins ability to take up glucose in the muscles and peripheral tissues. This causes more glucose to remain in the blood and an increased rate of gluconeogenesis by the liver.

Growth hormone disorders result from either too much or too little HGH. Hypersecretion of HGH from the pituitary leads to gigantism or acromegaly. HGH deficiency leads to short stature in children or GH deficiency syndrome in adults.

Acromegaly is most commonly caused by a brain tumoran HGH secreting pituitary adenoma. The excess HGH continues to add bone to closed epiphyseal growth plates in flat bones on the skull, mandible, sternum, hands, and feet.

Facial features include deep nasolabial furrows, prominent supraorbital ridges and enlargement of the nose and lips. Often the presenting complaint is of hats or gloves not fitting anymore due to swelling of the hands and head, although excessive sweating and headaches are also common.

If the mass gets large enough it can cause reproductive disorders and or affect ones vision. In addition to bony growth, HGH causes heart tissue to grow and harden in a process called biventricular concentric hypertrophy putting you at risk of heart failure.

Because HGH counteracts the effects of insulin on glucose and lipid metabolism, diabetes mellitus type 2 and hyperlipidemia are strongly associated with this disease. Treatment consists of surgery and radiation therapy targeting the underlying adenoma as well as symptomatic relief of the secondary effects of HGH as above.

If the HGH from the underlying pituitary adenoma acts on the long bones before the growth plate of the long bone closes then gigantism results. Since epiphyseal closure occurs before adulthood, this is typically an illness with an onset seen in children. The organ and metabolic impacts are similar to acromegaly.

In children, idiopathic HGH deficiency is most common. If HGH deficiency appears during adulthood it typically presents alongside a constellation of other hypopituitary deficiencies. A prolactinoma, a pituitary tumor that over-secretes the hormone prolactin typically triggers HGH deficiency, although radiation or surgery can be the culprit.

Adult-onset HGH deficiency is typically harder to diagnose than idiopathic HGH deficiency because the symptoms are nonspecific and no single identifying feature s pathognomonic.

Adults can have decreased skeletal muscle, increased belly fat, and early-onset osteoporosis. Dyslipidemia and insulin resistance are prevalent, which lead to secondary cardiovascular dysfunction, depressed mood, increased anxiety, and a lack of energy.

HGH induces growth in nearly every tissue and organ in the body. However, it is most notorious for its growth-promoting effect on cartilage and bone, especially in the adolescent years. Therefore, hGH is most often used to treat poor growth in children and adults.

Special blood tests can detect human growth hormone deficiencies in children and adults. Human growth hormone injections not only ameliorate short stature but also protects fractures, increases energy, improves exercise capacity, and reduces risk of future heart disease.

HGH has also been highly touted anecdotally for its anti-aging effects but these claims have not been supported by research.

Up to 30% of those who take HGH experience side effects including:

Some athletes use recombinant human growth hormone (rhGh) to improve their athletic performance and get a competitive advantage. Taking rhGH not only increases muscle mass, but it also enhances recovery. The drug has been found in swimmers and also in players taking part in major sports events.

The World Anti-Doping Agency and the International Olympic Committee have had HGH on the list of forbidden compounds since 1989, when it became obvious that the development of biotechnology products based on the recombination of DNA made hGH much more easily available on the regular and black markets.

Sports leagues including Major League Baseball and the National Football League have also banned its use.

As previously mentioned, HGH can have many adverse side effects. Also, HGH is injected intramuscularly or subcutaneously so there may be injury at the injection site. Lastly, HGH sold on the street can be laced with other drugs increasing your risk of experiencing a bad outcome.

HGH should only be taken under the watchful eye of a healthcare professional. If you are thinking about using HGH, consult a healthcare professional as HGH should only be taken for medical conditions that necessitate its use.

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Reed ML, Merriam GR, Kargi AY. Adult growth hormone deficiency - benefits, side effects, and risks of growth hormone replacement.Front Endocrinol (Lausanne). 2013;4:64. doi:10.3389/fendo.2013.00064

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By Shamard Charles, MD, MPH Shamard Charles, MD, MPH is a public health physician and journalist. He has held positions with major news networks like NBC reporting on health policy, public health initiatives, diversity in medicine, and new developments in health care research and medical treatments.

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Human Growth Hormone (HGH): What is it, Levels, and More - Verywell Health