What Growth Hormone Does
by Benjamin Bunting BA(Hons) PGCert
Written by Ben Bunting: BA(Hons), PGCert. Sport & Exercise Nutrition. L2 Strength & Conditioning Coach.
Human Growth hormone (HGH) is one of the body’s main anabolic hormones and is essential for the proper development of the body.
Hormones are chemical messengers that are produced by various glands (hormone factories) that help stimulate and regulate various functions of the body including growth.
Whether you’re increasing your muscle mass or losing the excess fat in your body, hormones interplay with each other to execute these functions properly.
In this article we shall cover the following key points:
- How is growth hormone produced?
- Growth hormone functions
- Will growth hormone build muscle?
- Side effects
How is growth hormone produced?
HGH is synthesized by the anterior pituitary gland. The anterior pituitary and posterior pituitary together make up the pituitary gland, also known as the master gland of the body.
Hormones produced by the pituitary gland regulate almost all the other glands of the body. Growth hormone (GH) is synthesized as a 191 amino-acid polypeptide in the somatotrophic cells of the anterior pituitary.
Due to its location of synthesis, it is also known as somatotropin hormone. Just like many other man-made hormones, technology has made it possible to reproduce GH outside the human body.1
Natural growth hormone production
The somatotrophic cells are stimulated and controlled by another regulatory part of the brain, the hypothalamus.
Hypothalamus synthesizes and secretes growth-hormone-releasing hormone (GHRH) which stimulates the release of GH from the pituitary. T
o put it simply, the brain assesses various needs and circumstances the body is in and then sends signals for the release of growth hormone.
For instance, if you start working out in the gym, your brain will sense the need for muscle growth and begin the GH-producing cascade.
Apart from the body’s natural resources, growth hormone has been made available through several techniques for various uses.
At present, recombinant DNA (rDNA) technology is being used to manufacture human growth hormone and various other hormones like insulin, etc. Before the invention of rDNA technology, the HGH was extracted from the pituitary glands of the cadavers, and as gross as it sounds, it is true.2
The advent of recombinant genetic technology has saved us from the gruesome side effects of cadaveric-extracted growth hormone supplements.
The procedure comprises several steps that end in a pure human growth hormone. Firstly, the genes that are responsible for the synthesis of GH are extracted from the human somatotrophic cells and placed in another genetic material, such as bacterial DNA.
Genes are extracted by a clever method called isolation. In a normal cell, genes are used to make mRNA which is a code for protein (i.e., GH). This mRNA is extracted and turned into cDNA (complementary DNA).
Secondly, the cDNA is placed into a plasmid which is the circular genetic material in the bacteria.
The bacteria are then cultured (multiplied) in millions. These bacteria then use this genetic material to produce the GH. Lastly, the product is extracted and used as a recombinant HGH.3
Functions of growth hormone
As the name suggests growth hormone is responsible for growth in nearly all the tissues of the body. Whether it is bone, cartilage, or muscles increased growth hormone will push these tissues to grow rapidly.
The most significant effect of growth hormone, however, is on the bone and cartilage tissues. Bones and cartilages are formed and sustained by specialized cells called osteoblasts and chondrocytes, respectively1,4.
HGH directly activates these cells helping them divide and increase their size leading to growth. And particularly for the athletic audience, HGH has well-known and documented effects on the manufacturing of protein i.e., muscle tissue.
We will look further into the effects of growth hormone on muscle tissue in the subsequent text.
While human growth hormone is notorious for growth around the body i.e., anabolic effects it also has metabolic effects.
Metabolic effects refer to processes in the body that lead to the breakdown of complex compounds. A good example would be the stored fat being burnt (broken down and used) for providing energy.
The most pronounced metabolic effects of growth hormone include the metabolism of fats and the effects on insulin. HGH stimulates the adipose tissue (fat stores) via another hormone called insulin-like growth factor-1 (IGF-1).
In fat cells, these two hormones upregulate the fat degrading enzymes, like hormone-sensitive lipase, which breaks down triglycerides into fatty acids that are then utilized for energy or heat.
Another interesting feat of HGH, along with IGF-1, is their antagonizing effects on insulin5. Insulin, as you might know, primarily functions to control blood sugar levels.
Insulin has a systemic hypoglycemic effect along with an overall anabolic effect on the body. This means that if you have got enough insulin your blood glucose levels will stay in the normal range.
Insulin also promotes fat storage (increase adipose tissue) and muscle cells growth. HGH stops insulin from acting on peripheral cells e.g., fat cells, and decreases their glucose uptake.
It, therefore, increases the blood glucose levels and is also referred to as a diabetogenic (blood-glucose increasing) hormone.5,6
Will growth hormone build muscle?
For most people, this is one of the hottest topics related to growth hormone. As mentioned above, HGH promotes muscle tissue growth.
The further discussion will focus on how growth hormone makes the body look bulky, provides strength, and stay lean at the same time.
Focusing on protein metabolism, there are two main hormones in our body working as anabolic hormones, insulin, and GH.
These hormones act via similar intracellular pathways to carry out their functions, however, they function at different times of the day. Just after eating food, the STAT 5 intercellular pathway (a signaling pathway for action of GH and insulin) is ruled by insulin.
However, at times of stress like physical activity, pushing weights, and/or fasting growth hormone is the body’s choice for anabolic effects. With this in mind let us look at some studies that indicate whether and how much HGH affects your muscular tone.
Considering endogenous (made by the body) HGH, increases muscular hypertrophy, strength, and the body’s overall development is increased.
A very known cause for an increase in muscle mass is resistance training or weight training.
Resistance training is associated with increased amounts of endogenous anabolic hormones (including GH) promoting the fact that GH can help gain extra gain. Should the exogenous (from outside the body) GH produce the same effects?7
Earlier use of GH was thought to promote extreme muscle growth and this belief is still prevalent. This has led to the abuse of GH by bodybuilders and athletes in an attempt to increase muscle mass and strength.
Growth hormone doesn't have a significant effect on muscle
However, an extensive review of the literature gives us a divided opinion about the effects of GH on muscle hypertrophy (increase in the size of the muscle cells).
Contrary to the customary belief, recent studies show that the use of recombinant human growth hormone (rHGH) has slim effects on muscle mass.
As for today, there is no concrete evidence about growth hormone’s muscle and strength building effects requiring more abstract research.8
In 1993, a study was carried out to test the hypothesis that low GH/IGF-1 in elderly people (over 60 years) leads to decreased strength and muscle mass.
The study showed that individuals using GH supplementation had positive growth in their lean muscle mass, muscle mass, and thigh strength. It should be noted, however, that there were no acute effects of GH on muscle mass or strength.
The study also eluded that GH does have the capacity of increasing muscle mass and strength but does not increase the rate of myofibrillary protein synthesis (the cellular components for muscle contraction).9
Another study carried out to assess the short-term effects of GH infusion in the body indicated that GH stimulates protein synthesis.
Subjects were given GH locally through infusion and several variables were noted. These variables included glucose uptake in cells and various amino acids. The study suggested locally infused GH stimulates skeletal muscle growth.10
In the review of the effects of rHGH, an extensively written article from the British Journal of Sports Medicine (BJSM) appeared to be most conclusive. It describes detailed effects of GH on the body including glucose, lipid, and protein metabolism.
The article states that GH does have anabolic effects but exogenous administration of rHGH, e.g., by athletes, does not have any significant effect on muscle hypertrophy and strength increase.
It was suggested that there were other effects of GH on the body’s metabolism that may have given a perception of muscle hypertrophy.8
Firstly, and as stated above, infusion of GH transiently increases the amino acids in that specific area (locally) e.g., increase in the forearm size.
However, this effect is not long-term and hasn’t been proven in another well-established study.
Secondly, GH has a very pronounced effect on fat metabolism i.e., lipolysis and fat distribution. It works to decrease body fat and distribute it more proportionately over the body.
This particular effect increases the lean body mass (not whole-body muscle mass) and the body appears to have skeletal muscular hypertrophy.
Having less body fat will make the body look more muscular or bulkier to some extent.
Thirdly, most people use rHGH while performing resistance training. As stated already, resistance training is known to increase whole-body muscle mass. Most athletes, therefore, confuse the gains caused by resistance training as a direct GH effect.
This might be the reason for the abuse of GH in the attempt to have super muscular gains.8,11
Various other studies were performed to assess the value of GH administration. Two groups were asked to perform various resistance training exercises with and without GH administration.
The results showed no beneficial effect of GH on the body’s protein synthesis, muscle mass, and strength. This applied to both young and old healthy subjects.11,12
The above discussion is limited mostly to people with normal GH levels in their bodies. It should be noted that the use of rHGH in GH deficient people has been established through clinical studies.
Almost all the patients with muscle wasting diseases like chronic kidney disease, HIV, and growth hormone deficiency were corrected (to a variable extent) by the administration of rHGH.13–15
Side effects of growth hormone
Despite what research suggests, growth hormone is being used by many athletes and trainers as a means to increase athletic performances and muscular hypertrophy.
The downside to the excessive (supraphysiological) use of growth hormone is its dangerous side effects profile.
The side effects range anywhere from a mild rise in blood sugar to fatal arrhythmias and sudden cardiac death.
The following discussion will focus on the most common adverse effects produced by the use or abuse of rHGH.
Decrease in strength
While most people take GH in an attempt to increase muscle mass and strength, recent study outcomes come with bad news.
Studies carried out in the Danish Institute of Sports Medicine showed that exogenous hGH administration decreased athletic endurance.
The pronounced increase in lipolysis, lactate, and H+ production in the body leads to metabolic acidosis (higher than normal pH of the body) leading to fatigue and decreased strength.
Moreover, due to the depletion of hepatic (liver) and muscle glycogen stores, the recovery of muscles after a workout is reduced.
Acromegaly is a disease caused by excess growth hormone. The presence of excess growth hormone in the body will eventually produce some growing effects.
One of the most common adverse effects of long-term use of hGH in adults is the enlargement of various bones in the body. Most significantly, the mandible (jaw bone) and bones of extremities (hands and feet) are affected.
The jaw starts to protrude outwards while fingers and toes get abnormally large. Moreover, patients with acromegaly often experience comorbidities like diabetes, osteoarthritis, and even colorectal cancer.16–18
Growth hormone does not only cause an increase in skeletal muscles (physiological) and bones it also affects the heart muscles.
HGH excess is related to excessive growth and enlargement of cardiac myocytes leading to a condition known as cardiac hypertrophy.
Cardiac hypertrophy leads to impaired left-ventricular function that causes decreased blood flow to organs of the body.
Having an abnormally large heart is also one of the leading causes of sudden cardiac death in young adults.19
Diabetes and fatty change
Growth hormone belongs to the diabetogenic group of hormones. These hormones have anti-insulin-like effects and tend to raise blood glucose levels.
Chronic use of supra-pharmacological (higher than needed) doses of hGH increased blood glucose levels by inhibiting glycogenesis and increasing glycogenolysis and gluconeogenesis.
Having a constantly elevated blood glucose level leads to various diabetic problems like diabetic neuropathy and retinopathy.
Alteration of the carbohydrate and fat metabolism also leads to excess fatty acids and lipids in the circulation.
When combined with exercises, people having raised hGH levels produce a lot of free fatty acids which are associated with sudden cardiac death.20–22
Risk of Cancer
This is one of the scariest concerns regarding the use of rHGH. The study was performed to assess the risk of cancer or malignancy in patients with acromegaly i.e., chronic excess of GH.
Subjects were at the highest risk of developing colorectal cancer, followed by breast, gastric, and urinary tract cancers.
Increased risk of thyroid cancer is also an established association with excess GH. The cancerous effects could be due to the growth-promoting effects of HGH.16
Banned in the military
With these unwanted and dangerous side effects, it should come as no surprise to learn that human growth hormones are banned in the military and are also banned in competitive sports.
Any athlete caught using groth hormones should expect to be banned from competing and any soldier using growth hormones should expect to be discharged.
The extensive of various articles and studies give us an idea of what growth hormone actually does.
It is one of the crucial hormones of the body needed for normal development. GH deficient people often have short stature, decreased strength, and experience dwarfism.
On the other hand, excess GH also has deleterious effects like acromegaly, cardiac dysfunction, and even cancer.
Recombinant human growth hormone or rHGH is successful in the treatment of various GH deficient states e.g., dwarfism.
However, as the current research suggests, rHGH has no beneficial effects for increased athletic performance in healthy individuals.
- Brinkman JE, Tariq MA, Leavitt L, Sharma S. Physiology, Growth Hormone. StatPearls. Published online May 7, 2021. Accessed February 9, 2022. https://www.ncbi.nlm.nih.gov/books/NBK482141/
- The big story behind synthetic human growth hormone | National Museum of American History. Accessed February 9, 2022. Available at: https://americanhistory.si.edu/blog/2012/10/human-growth-hormone.html
- What Are the Benefits of Proteins Produced Through Recombinant DNA Technology? Accessed February 9, 2022. https://sciencing.com/benefits-proteins-produced-through-recombinant-dna-technology-2044.html
- Akkiraju H, Nohe A. Role of Chondrocytes in Cartilage Formation, Progression of Osteoarthritis and Cartilage Regeneration. Journal of developmental biology. 2015;3(4):177. doi:10.3390/JDB3040177
- Kim SH, Park MJ. Effects of growth hormone on glucose metabolism and insulin resistance in human. Annals of Pediatric Endocrinology & Metabolism. 2017;22(3):145. doi:10.6065/APEM.2017.22.3.145
- Møller N, Jørgensen JO, Møller J, et al. Metabolic effects of growth hormone in humans. Metabolism: clinical and experimental. 1995;44(10 Suppl 4):33-36. https://doi.org/10.1016/0026-0495(95)90218-X
- Fink J, Schoenfeld BJ, Nakazato K. The role of hormones in muscle hypertrophy. The Physician and sportsmedicine. 2018;46(1):129-134. https://doi.org/10.1080/00913847.2018.1406778
- Rennie MJ. Claims for the anabolic effects of growth hormone: a case of the Emperor’s new clothes? British Journal of Sports Medicine. 2003;37(2):100-105. http://dx.doi.org/10.1136/bjsm.37.2.100
- S W, C T, M S, B M. Growth hormone increases muscle mass and strength but does not rejuvenate myofibrillar protein synthesis in healthy subjects over 60 years old. The Journal of clinical endocrinology and metabolism. 1996;81(9):3239-3243. https://doi.org/10.1210/jcem.81.9.8784075
- Fryburg DA, Gelfand RA, Barrett EJ. Growth hormone acutely stimulates forearm muscle protein synthesis in normal humans. https://doi.org/101152/ajpendo19912603E499. 1991;260(3 23-3). doi:10.1152/AJPENDO.1991.260.3.E499
- Yarasheski KE, Campbell JA, Smith K, Rennie MJ, Holloszy JO, Bier DM. Effect of growth hormone and resistance exercise on muscle growth in young men. https://doi.org/101152/ajpendo19922623E261. 1992;262(3 25-3). doi:10.1152/AJPENDO.1992.262.3.E261
- Yarasheski KE, Zachwieja JJ, Campbell JA, Bier DM. Effect of growth hormone and resistance exercise on muscle growth and strength in older men. https://doi.org/101152/ajpendo19952682E268. 1995;268(2 31-2). doi:10.1152/AJPENDO.1995.268.2.E268
- Salomon F, Cuneo RC, Hesp R, Sönksen PH. The Effects of Treatment with Recombinant Human Growth Hormone on Body Composition and Metabolism in Adults with Growth Hormone Deficiency. New England Journal of Medicine. 1989;321(26):1797-1803. https://www.nejm.org/doi/full/10.1056/NEJM198912283212605
- Cuneo R, Salomon F, Wiles M, … JRHR in, 1992 undefined. Histology of skeletal muscle in adults with GH deficiency: comparison with normal muscle and response to GH treatment. karger.com. Accessed February 12, 2022. https://www.karger.com/Article/Abstract/182276
- Butterfield GE, Thompson J, Rennie MJ, Marcus R, Hintz RL, Hoffman AR. Effect of rhGH and rhIGF-I treatment on protein utilization in elderly women. American Journal of Physiology - Endocrinology and Metabolism. 1997;272(1 35-1). https://doi.org/10.1152/ajpendo.1997.272.1.E94
- Dal J, Leisner MZ, Hermansen K, et al. Cancer Incidence in Patients With Acromegaly: A Cohort Study and Meta-Analysis of the Literature. The Journal of Clinical Endocrinology & Metabolism. 2018;103(6):2182-2188. https://doi.org/10.1210/jc.2017-02457
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- Perpignano G, Cacace E, Beccaris A, et al. Acromegalic arthropathy. La Clinica terapeutica. 1993;143(1):3-9. Available at: https://pubmed.ncbi.nlm.nih.gov/8243021/