Human Growth Hormone, also known as Somatotropin, and abbreviated as HGH (or more commonly, GH) is a peptide hormone produced in the pituitary gland. To be more specific, HGH is a “mitogen” produced and stored in somatrophic cells found within the anterior pituitary gland. A mitogen is any chemical substance that encourages a cell to divide, triggering mitosis. Ultimately, this mitosis leads to a growth of new tissue. For bodybuilders, the single most important effect of GH is the mitogenic effect on muscle tissue. Interestingly, studies recently performed to test the effect of GH on new muscle growth have largely been unimpressive, and in some cases have shown little in the way of results. Nevertheless, it is believed that the main contributing factor to the increased size seen in modern bodybuilders, aside from the advancements in nutrition and exercise, is largely due to Growth Hormone use.
Growth hormone is known as a stress hormone, and increases glucose and fatty-acid release into the bloodstream . Cortisol is another stress hormone that most readers are familiar with. While cortisol and growth hormone both increase glucose and fatty acids during times of stress, GH typically increases markers of body composition, while Cortisol negatively affects them. Nevertheless, it’s important to understand that GH increases glucose and lowers insulin sensitivity. Users of high doses of GH have reported hyperglycemia, which is usually treated by increasing insulin use, which is considered dangerous and poses its own health risks. Growth Hormone also increases IGF-1, which accounts for many of GH’s positive benefits. Indeed, IGF-1 facilitates glucose uptake and may enhance insulin sensitivity, so in many cases, the negative effects of GH on glucose can be normalized when IGF-1 levels increase.
When talking about Growth Hormone it’s important to make a distinction between the different terms used loosely to describe it. Somatotrophin is the technical term for Growth Hormone, and may be sometimes called Somatotrophic Hormone. Somato refers to “whole body” and Trophin is used to describe it’s hormonal nature. Growth Hormone that is produced and manufactured for human consumption is called recombinant Human Growth Hormone, or rhGH for short. Somatropin is a generic term used to described rhGH, while the brand name Humatrope refers to the brand name form of Somatropin, marketed by Lily Pharmaceuticals.
Natural Growth Hormone Regulation
The secretion, or release, of GH by the pituitary is regulated by the Hypothalamus. These two parts of the brain are responsible for regulating a number of hormones including Testosterone. During periods of fasting (low blood sugar or caloric intake) or sleep, the Hypothalamus releases GHRH (Growth Hormone Releasing Hormone). This hormone reaches the Pituitary gland which then secretes GH in a pulsatile manner (meaning in short burts). The largest pulse occurs about an hour into sleep, while various pulses occur throughout the day and vary in strength. These pulses occur while the body is fasted, and therefore “stressed” (which is why Growth Hormone is called a stress hormone) which helps provide glucose and fatty acids to be used for energy by the cells of the body. Nearly 50% of Growth Hormone is released during sleep, in the REM stages to be more precise.
Several factors affecting the release of Growth Hormone are worth noting. Age is the most important factor. Younger adults or adolescents, secrete about 700 nanograms per day, while healthy adults release about 400 nanograms. Sleep deprivation has a large impact on GH release, especially after adolescence. Other factors include nutritional status (glucose ingestion inhibits GH release) and exercise (vigorous exercise increases Growth Hormone release). Certain amino acids affect GH release, such as Arginine, Agmatine and Ornithine, but a fasted, or low blood sugar state is still necessary to inhibit GHIH(Growth Hormone Inhibiting Hormone, or Somatostatin) which is also released by the Hypothalamus, which then signals the Pituitary gland to stop secreting GH.
Growth Hormone Effects & Benefits
Most of the studies done on Growth Hormone pertain to its effects on connective tissue development and growth, as well as its effect on glucose metabolism and body composition. Because Growth Hormone is a polypeptide hormone (It is essentially a long chain of amino acids, 191 amino acids in length to be precise) it does not actually penetrate the cells of the body. Instead it activates receptors outside the cell. One of those receptors, and the one most responsible for Growth Hormone’s effect on cartilage regeneration, is the MAPK/ERK pathway. While muscle cells also have MAPK/ERK receptors, many studies have contradicted the common belief that Growth Hormone affects new muscle cell growth, outside of the context of the growing adolescent body. To be more specific, most studies looking at Growth Hormone’s effects on “hyperplasia” or new muscle cell growth, tend to show little to no results in older adults. Only during the puberty stage does Growth Hormone seem to affect muscle cell growth in such a dramatic way. Nevertheless, Growth Hormone is incredibly popular in the world of athletics and bodybuilding and for good reasons.
Growth Hormone also stimulates IGF-1 through a pathway known as the JAK-STAT pathway. IGF-1 is an abbreviation for Insulin-like Growth Factor 1. IGF-1 is responsible for the effects on growth that we usually attribute to Growth Hormone. While Growth Hormone is effective in altering body composition through fat loss, and muscle preservation, IGF-1 is considered by many to be the main contributing factor to new muscle growth seen in GH users. While many studies have been done on Growth Hormone and show little to no effect on muscle growth, it is believed that those studies are not conducted long enough to show the effect that IGF-1 has on muscle tissue development. More studies are needed before a true scientific consensus can be reached.
Nevertheless, IGF-1 has many positive effects on a wide variety of tissues and a special form of IGF-1, known as Mechano-Growth Factor, or MGF, is released within cells that is widely known as the primary factor in muscle development. IGF-1 also has stimulatory effects on bone growth, and has potent osteoblast activity.
In addition to its primary effect on glucose metabolism, IGF-1 also possesses the following benefits:
- Increases Calcium retention, leading to increases of bone density.
- Increase Sarcoplasmic Hypertrophy (increase in muscle cell volume).,
- Promotes the release of fatty acids, known as “Lipolysis”.
- Increases protein synthesis.
- Promotes the production of glucose in the liver, known as Gluconeogenesis
- Stimulates the immune system.
- Increases the conversion of T4 hormone into T3.
Acromegaly is a disease of excessive Growth Hormone production, usually caused by a tumor in the pituitary gland. This excessive GH release can lead to a number of life-threatening effects such as type 2 diabetes, carpal tunnel syndrome, excessive thickening of the jaw, fingers and toes, and may cause impaired vision due to pressure on the optic nerves. In most instances of Acromegaly, removal of the tumor can prevent these side effects and in other instances, a combination of drug therapy is recommended. Drugs that reduce the signal of Growth Hormone release (Somatostatin releasers) as well as drugs that activate dopamine neurons (due to Dopamine’s inhibitory effect on GH release) can be used successfully to control GH release without dangerous surgery or radiation treatment.
Clinical Effects of Growth Hormone Deficiency
The clinical effects of Growth Hormone deficiency depend on the age at which the deficiency occurs. During adolescence, a period of time where maximal height and sexual characteristics are expressed, a deficiency in this hormone can result in stunted growth and may require the use of rhGH therapy in order to address this disease.
Growth hormone deficiency in adults is very rare, however as we age, GH levels begin to diminish rapidly. In some cases however, total loss of GH output can occur, and this requires extensive testing to determine the cause and nature of the disease. Adults with Growth Hormone Deficiency (GHD) will tend to have a relative increase in fat mass as well as catabolism, or loss of muscle tissue. As well, those who suffer from GHD may experience lethargy, and decreased energy levels. Often times these symptoms can be reversed using rhGH or GH stimulating peptides such as Sermorelin a GHRP designed to signal the hypothalamus to release Growth Hormone in a pulsatile manner.
Off Label Use
Early studies using GH replacement therapy in men over the age of 60 showed an increase in muscle mass and a decrease in fat storage as well as increased bone mineral density. While these results are promising, they in no way indicate that Growth Hormone reverses the aging process, therefore it cannot be technically labeled an “anti-aging” compound. Nevertheless, early adopters of the research latched onto this concept and promoted GH replacement therapy as a way to halt and even reverse the aging process. To date, the prescribing of GH for any other condition besides primary GH insufficiency is considered to be illegal.
In addition to studies done on anti-aging benefits, multiple studies have been completed to evaluate Growth Hormone’s role in treating neurological conditions such as Multiple Sclerosis, fibromyalgia, Crohn’s disease and Ulcerative Colitis.
Currently, it is considered a felony in the United States to prescribe Growth Hormone for any condition other than the medically recognized conditions stated above.
Side Effects of Growth Hormone
Some common side-effects of Growth Hormone include joint swelling, carpal tunnel syndrome, insulin resistance, which can sometimes lead to type 2 diabetes. In rare cases, the patient can develop an immune response to exogenously administered Growth Hormone and in even more rare circumstances, GH replacement can be a risk-factor for Hodgkin’s Lymphoma.
While many studies have been conducted showing little to no benefit of Growth Hormone on parameters of athletic performance, GH misuse continues rampantly in athletic sports. Most recently, NFL players such as Peyton Manning and pro cyclist Lance Armstrong have been accused of using Growth Hormone for its effects on injury recovery, muscle acquisition and general performance enhancement.
Many supplement manufacturers have attempted to capitalize on the hype surrounding Growth Hormone benefits by creating various supplements that purportedly increase Growth Hormone output. Most notably, the amino acids Arginine and Ornithine have been shown to modestly boost Growth Hormone levels, although the positive benefits of this supplementation regimen have been mostly unimpressive. Nevertheless, many supplements on the market today are sold as being precursors to Growth Hormone or stimulators of GH release, and continue to sell well in the health and wellness marketplace.
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