Human growth hormone supplements are all the go nowadays.
According to the companies and ex-basketball stars that peddle them, they’re the answer to increased muscle growth and fat loss, child-like energy levels, and deep, restful sleep.
And if you’re like many folks, this sounds too good to be true.
Is there really such a thing as a natural “HGH booster?”
Is there any science behind these products?
And even if they work, are human growth hormone supplements safe?
Get an evidence-based answer in this article.
What Is Human Growth Hormone?
Human growth hormone (HGH), also known as somatropin or simply “growth hormone,” is a hormone produced by the pituitary gland.
HGH is responsible for regulating growth during childhood and adolescence, though it also figures prominently in fat burning and muscle growth.
Specifically, HGH causes fat “mobilization,” which means it helps your body release the fatty acids stored in fat cells, and it promotes the release of insulin-like growth factor 1 (IGF-1), which triggers muscle growth, blunts muscle breakdown, and further encourages fat mobilization.
What Are Human Growth Hormone Supplements?
Human growth hormone supplements are dietary supplements that contain ingredients purported to increase your body’s HGH levels.
They differ from human growth hormone injections, which are a medical treatment that doctors administer to people with human growth hormone deficiency and conditions associated with poor growth.
Some bodybuilders also use human growth hormone injections to boost their HGH to supraphysiological levels, hoping to increase muscle gain and fat loss beyond what’s possible naturally. Using human growth hormone injections in this context is illegal and can harm your health.
For example, research shows that using human growth hormone for bodybuilding can hinder heart health, cause insulin resistance, and increase your risk of blood, breast, colon, prostate, and endometrial cancer.
Human Growth Hormone Supplements: Benefits
The most commonly claimed benefits of human growth hormone supplements are increased muscle growth, strength, fat loss, and energy, accelerated recovery from training, fewer aches and pains, and improved mood and sleep.
To achieve this, supplement companies create supplements containing gobs of ingredients, all of which, they say, boost HGH production.
Are these ingredients really beneficial, though?
Let’s look at what science says about some of the most common HGH supplement ingredients to find out.
Lysine
Lysine, or L-lysine, is an essential amino acid (an amino acid your body must obtain through your diet) that plays a part in muscle protein synthesis and cellular function.
Research shows that supplementing with lysine alone doesn’t boost HGH levels.
While some research shows that combining lysine with the amino acid arginine may increase HGH levels, other studies show the increase is too small to make any meaningful difference to body composition.
Therefore, there’s little evidence that supplementing with lysine increases HGH levels to a significant degree.
Arginine
Arginine, or L-arginine, is an amino acid that your body uses to synthesize nitric oxide, a substance that relaxes your blood vessels, regulates blood flow, and improves athletic performance.
Similarly to lysine, taking arginine alone doesn’t boost HGH. This may change when combined with lysine, but this evidence is inconclusive.
One study published in The Journal of Sports Medicine and Physical Fitness showed that combining arginine with the amino acid ornithine significantly increased HGH levels in men who also followed a weightlifting program.
There are two problems with this study, though.
First, several studies show that strength training alone increases HGH levels. As such, it’s impossible to know whether the participants experienced increased HGH because of the supplement or because they lifted weights.
Second, subsequent research has called into question the methods the scientists used. For example, the authors measured the participants’ weight using a spring scale, their body fat percentage using calipers, and their body fat mass using a tape measure, which are all prone to significant error.
Another study published in the Journal of Strength and Conditioning Research found that men who supplemented with arginine and ornithine had higher HGH levels than men who took a placebo after completing a weightlifting workout.
The same problem persists, however: The participants took two supplements, making it impossible to know which was responsible for the increase in HGH. What’s more, studies using similar supplement combinations have failed to replicate the results.
At bottom, there’s almost no reason to believe arginine affects HGH levels.
Ornithine
Ornithine is an amino acid that’s involved in the urea cycle, a process that balances out urea and ammonia levels in the body.
As we’ve already seen, studies looking at the effect of taking ornithine and arginine on HGH are inconclusive. Similar research shows that taking ornithine in combination with tyrosine doesn’t raise HGH levels, either.
Results from studies investigating how ornithine alone affects HGH show that taking large doses may increase HGH for a short time. Although this result seems encouraging, there are two caveats.
First, to raise HGH levels, you have to take an impractically large dose of ornithine that’s highly likely to cause severe stomach cramps and diarrhea.
Second, these studies only consider HGH changes over 90 minutes. For growth hormone to have an appreciable effect on muscle building and fat loss, it needs to be elevated for far longer (days or even weeks).
Taken together, there’s little evidence that ornithine meaningfully increases HGH levels.
Glutamine
Glutamine is the most abundant and versatile amino acid in the body.
Most research looking at glutamine’s effect on HGH levels is conflicting, with some studies showing taking glutamine increases HGH (at least for a short while) and others demonstrating the opposite (even after weightlifting).
In one notable study conducted by scientists at the Pennington Biomedical Research Center, researchers found that taking a supplement containing glutamine (as well as lysine, arginine, and several other ingredients) increased HGH levels by 682% after just 2 hours.
(The same lab released a subsequent paper detailing the mechanisms behind this staggering result.)
While these results seem promising, the scientists who conducted the study work for the company that makes the supplement they used. Thus, it’s probably sensible to be chary of these findings until a disinterested third party replicates them (which hasn’t yet happened).
Gamma Aminobutyric Acid (GABA)
Gamma-aminobutyric acid (GABA) is a special type of amino acid that acts as an “inhibitory” neurotransmitter, which means it prevents chemical messages from being passed from neuron to neuron.
It also plays a key role in reducing stress and inducing sleep.
While research shows that taking GABA post exercise can increase HGH levels, the increases are too tiny and temporary to affect body composition.
Deer Antler Velvet
Deer antler velvet is the soft hair that covers a deer’s (or elk’s) antlers that’s been used in traditional Chinese medicine for millennia.
To make deer antler velvet supplements, supplement companies remove a deer’s antlers, then strip, dry, and grind the velvet into a powder. The powder is then packed into pills or dissolved in liquid, ready for ingestion.
Deer antler velvet contains IGF-1. Since HGH and IGF-1 are closely related, many people think that taking deer antler velvet may boost HGH.
However, there’s no evidence that supplementing with deer antler velvet increases IGF-1 or HGH.
Mucuna Pruriens
Mucuna pruriens, also commonly known as velvet bean and cowhage, is a climbing shrub in the legume family that’s native to Africa and Asia and cultivated in North America. It produces hair-covered seeds that cause intense itching if they touch your skin.
These seeds contain levodopa (L-DOPA), which is an amino acid involved in the production of dopamine, a neurotransmitter that regulates your mood, cognition, and motivation to exercise.
While older research suggests supplementing with L-DOPA may increase HGH, there’s no evidence the increase is large or lasting enough to benefit body composition.
What’s more, there’s little reason to believe that taking Mucuna pruriens has a similar effect.
The only evidence comes from a study conducted by scientists at the University of Memphis, in which participants experienced an increase in HGH after taking a supplement containing Mucuna pruriens and safed musli.
Given that the supplement contained two ingredients, the participants exercised regularly (although not within 48 hours of the study), and a supplement company that sells the supplement used in the study funded the research, it’s difficult to know how reliable these results are.
Thus, there’s no strong evidence that Mucuna pruriens boosts HGH.
Astragalus
Astragalus is a herb used in traditional Asian medicine, most often as a tonic or diuretic.
Some research on rats and rat cells suggests that astragalus may increase HGH secretion, but there’s no evidence that the same is true in humans.
Until we have more compelling research, it’s safe to conclude that astragalus doesn’t increase HGH.
Human Growth Hormone Supplements: Side Effects
Here’s a rundown of the most common side effects associated with the ingredients above:
- Lysine: Common side effects associated with taking large doses of lysine include nausea, vomiting, abdominal pain, diarrhea, skin rash, dizziness, and headache.
- Arginine: Arginine is generally considered safe, though some who take it may experience gastrointestinal upset.
- Ornithine: Taking large doses of ornithine can cause severe stomach cramps and diarrhea.
- Glutamine: Short-term glutamine use isn’t associated with any adverse side effects, though some research suggests long-term usage may negatively affect health in numerous ways, including compromising immune function, increasing cancer risk, and impairing gut and kidney health.
- GABA: Most studies suggest GABA is well-tolerated. That said, some people report feeling a burning sensation on the throat, breathlessness, lethargy, and weakness in the legs following GABA ingestion.
- Deer Antler Velvet: There are no known side effects associated with taking deer antler velvet.
- Mucuna Pruriens: Most people don’t experience negative side effects from taking Mucuna pruriens. However, because Mucuna pruriens contains L-DOPA, it can have the same side effects as levodopa, which include nausea, vomiting, anxiety, low blood pressure, and dyskinesia (involuntary muscle movements).
- Astragalus: Supplementing with astragalus may cause rash, itching, nasal symptoms, or stomach discomfort, but these are uncommon.
Conclusion
Despite what many supplement companies claim, there are very few natural ingredients that raise HGH levels in humans. Those that do, only increase HGH for a short while and not enough to significantly impact muscle gain and fat loss.
What’s more, HGH supplements often have adverse side effects. These side effects aren’t always dangerous, but they’re nonetheless undesirable.
Fortunately, there are more practical and reliable ways to increase HGH without taking supplements: lifting heavy weights and losing excess body fat.
Research routinely shows that intense weightlifting and lowering your body fat percentage increase HGH more than any legal supplement ever will.
And if you want an exercise program that includes plenty of heavy lifting and a diet plan designed to help you lose fat like clockwork, check out my fitness books for men and women, Bigger Leaner Stronger and Thinner Leaner Stronger.
(Or if you’re not sure if Bigger Leaner Stronger or Thinner Leaner Stronger is right for you, take the Legion Strength Training Quiz, and in less than a minute, you’ll know the perfect strength training program for you. Click here to check it out.)
Scientific References +
- Lu, M., Flanagan, J. U., Langley, R. J., Hay, M. P., & Perry, J. K. (2019). Targeting growth hormone function: strategies and therapeutic applications. Signal Transduction and Targeted Therapy 2019 4:1, 4(1), 1–11. https://doi.org/10.1038/s41392-019-0036-y
- Brinkman, J. E., Tariq, M. A., Leavitt, L., & Sharma, S. (2022). Physiology, Growth Hormone. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK482141/
- Hersch, E. C., & Merriam, G. R. (2008). Growth hormone (GH)–releasing hormone and GH secretagogues in normal aging: Fountain of Youth or Pool of Tantalus? Clinical Interventions in Aging, 3(1), 121. https://doi.org/10.2147/cia.s3247
- Anderson, L. J., Tamayose, J. M., & Garcia, J. M. (2018). Use of Growth Hormone, IGF-I, and Insulin for Anabolic Purpose: Pharmacological Basis, Methods of Detection, and Adverse Effects. Molecular and Cellular Endocrinology, 464, 65. https://doi.org/10.1016/J.MCE.2017.06.010
- Sigalos, J. T., & Pastuszak, A. W. (2018). The Safety and Efficacy of Growth Hormone Secretagogues. Sexual Medicine Reviews, 6(1), 45. https://doi.org/10.1016/J.SXMR.2017.02.004
- Clemmons, D. R. (2012). Metabolic Actions of IGF-I in Normal Physiology and Diabetes. Endocrinology and Metabolism Clinics of North America, 41(2), 425. https://doi.org/10.1016/J.ECL.2012.04.017
- Erotokritou-Mulligan, I., Holt, R. I., & Sönksen, P. H. (2011). Growth hormone doping: a review. Open Access Journal of Sports Medicine, 2, 99. https://doi.org/10.2147/OAJSM.S11626
- Tomé, D., & Bos, C. (2007). Lysine Requirement through the Human Life Cycle. The Journal of Nutrition, 137(6), 1642S-1645S. https://doi.org/10.1093/JN/137.6.1642S
- Ukmar-Godec, T., Hutten, S., Grieshop, M. P., Rezaei-Ghaleh, N., Cima-Omori, M. S., Biernat, J., Mandelkow, E., Söding, J., Dormann, D., & Zweckstetter, M. (2019). Lysine/RNA-interactions drive and regulate biomolecular condensation. Nature Communications 2019 10:1, 10(1), 1–15. https://doi.org/10.1038/s41467-019-10792-y
- Isidori, A., Lo Monaco, A., & Cappa, M. (1981). A study of growth hormone release in man after oral administration of amino acids. Current Medical Research and Opinion, 7(7), 475–481. https://doi.org/10.1185/03007998109114287
- Suminski, R. R., Robertson, R. J., Goss, F. L., Arslanian, S., Kang, J., DaSilva, S., Utter, A. C., & Metz, K. F. (1997). Acute effect of amino acid ingestion and resistance exercise on plasma growth hormone concentration in young men. International Journal of Sport Nutrition, 7(1), 48–60. https://doi.org/10.1123/IJSN.7.1.48
- Corpas, E., Blackman, M. R., Roberson, R., Scholfield, D., & Harman, S. M. (1993). Oral arginine-lysine does not increase growth hormone or insulin-like growth factor-I in old men. Journal of Gerontology, 48(4). https://doi.org/10.1093/GERONJ/48.4.M128
- Lambert, M. I., Hefer, J. A., Millar, R. P., & Macfarlane, P. W. (1993). Failure of commercial oral amino acid supplements to increase serum growth hormone concentrations in male body-builders. International Journal of Sport Nutrition, 3(3), 298–305. https://doi.org/10.1123/IJSN.3.3.298
- R P Elam, D H Hardin, R A Sutton, & L Hagen. (n.d.). Effects of arginine and ornithine on strength, lean body mass and urinary hydroxyproline in adult males - PubMed. Retrieved November 8, 2022, from https://pubmed.ncbi.nlm.nih.gov/2770269/
- Gotshalk, L. A., Loebel, C. C., Nindl, B. C., Putukian, M., Sebastianelli, W. J., Newton, R. U., Häkkinen, K., & Kraemer, W. J. (1997). Hormonal responses of multiset versus single-set heavy-resistance exercise protocols. Canadian Journal of Applied Physiology = Revue Canadienne de Physiologie Appliquee, 22(3), 244–255. https://doi.org/10.1139/H97-016
- Kraemer, W. J., Fleck, S. J., Dziados, J. E., Harman, E. A., Marchitelli, L. J., Gordon, S. E., Mello, R., Frykman, P. N., Koziris, L. P., & Triplett, N. T. (1993). Changes in hormonal concentrations after different heavy-resistance exercise protocols in women. Journal of Applied Physiology (Bethesda, Md. : 1985), 75(2), 594–604. https://doi.org/10.1152/JAPPL.1993.75.2.594
- Kraemer, W. J., Gordon, S. E., Fleck, S. J., Marchitelli, L. J., Melloo, R., Dziados, J. E., Friedl, K., Harman, E., Maresh, C., & Fry, A. C. (1991). Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. International Journal of Sports Medicine, 12(2), 228–235. https://doi.org/10.1055/S-2007-1024673
- Kraemer, W. J., Marchitelli, L., Gordon, S. E., Harman, E., Dziados, J. E., Mello, R., Frykman, P., McCurry, D., & Fleck, S. J. (1990). Hormonal and growth factor responses to heavy resistance exercise protocols. Journal of Applied Physiology (Bethesda, Md. : 1985), 69(4), 1442–1450. https://doi.org/10.1152/JAPPL.1990.69.4.1442
- Jacobson, B. H. (1990). Effect of Amino Acids on Growth Hormone Release. The Physician and Sportsmedicine, 18(1), 63–70. https://doi.org/10.1080/00913847.1990.11709950
- Zajac, A., Poprzȩcki, S., Zebrowska, A., Chalimoniuk, M., & Langfort, J. (2010). Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes. Journal of Strength and Conditioning Research, 24(4), 1082–1090. https://doi.org/10.1519/JSC.0B013E3181D321FF
- Fry, A. C., Kraemer, W. J., Stone, M. H., Warren, B. J., Kearney, J. T., Maresh, C. M., Weseman, C. A., & Fleck, S. J. (1993). Endocrine and performance responses to high volume training and amino acid supplementation in elite junior weightlifters. International Journal of Sport Nutrition, 3(3), 306–322. https://doi.org/10.1123/IJSN.3.3.306
- Fogelholm, G. M., Näveri, H. K., Kiilavuori, K. T., & Härkönen, M. H. (1993). Low-dose amino acid supplementation: no effects on serum human growth hormone and insulin in male weightlifters. International Journal of Sport Nutrition, 3(3), 290–297. https://doi.org/10.1123/IJSN.3.3.290
- Lambert, M. I., Hefer, J. A., Millar, R. P., & Macfarlane, P. W. (1993). Failure of commercial oral amino acid supplements to increase serum growth hormone concentrations in male body-builders. International Journal of Sport Nutrition, 3(3), 298–305. https://doi.org/10.1123/IJSN.3.3.298
- Bucci, L., Hickson, J. F., Pivarnik, J. M., Wolinsky, I., McMahon, J. C., & Turner, S. D. (1990). Ornithine ingestion and growth hormone release in bodybuilders. Nutrition Research, 10(3), 239–245. https://doi.org/10.1016/S0271-5317(05)80265-9
- Demura, S., Yamada, T., Yamaji, S., Komatsu, M., & Morishita, K. (2010). The effect of L-ornithine hydrochloride ingestion on human growth hormone secretion after strength training. Undefined, 01(01), 7–11. https://doi.org/10.4236/ABB.2010.11002
- Cruzat, V., Rogero, M. M., Keane, K. N., Curi, R., & Newsholme, P. (2018). Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation. Nutrients, 10(11). https://doi.org/10.3390/NU10111564
- Welbourne, T. C. (1995). Increased plasma bicarbonate and growth hormone after an oral glutamine load. The American Journal of Clinical Nutrition, 61(5), 1058–1061. https://doi.org/10.1093/AJCN/61.4.1058
- Tam, C. S., Johnson, W. D., Rood, J., Heaton, A. L., & Greenway, F. L. (2020). Increased human growth hormone following oral consumption of an amino acid supplement: results of a randomized, placebo-controlled, double-blind, crossover study in healthy subjects. American Journal of Therapeutics, 27(4), e333. https://doi.org/10.1097/MJT.0000000000000893
- Heaton, A. L., Kelly, C., Rood, J., Tam, C. S., & Greenway, F. L. (2021). Mechanism for the Increase in Human Growth Hormone with Administration of a Novel Test Supplement and Results Indicating Improved Physical Fitness and Sleep Efficiency. Journal of Medicinal Food, 24(6), 653. https://doi.org/10.1089/JMF.2020.0109
- Hepsomali, P., Groeger, J. A., Nishihira, J., & Scholey, A. (2020). Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Frontiers in Neuroscience, 14, 923. https://doi.org/10.3389/FNINS.2020.00923
- Diana, M., Quílez, J., & Rafecas, M. (2014). Gamma-aminobutyric acid as a bioactive compound in foods: a review. Journal of Functional Foods, 10, 407–420. https://doi.org/10.1016/J.JFF.2014.07.004
- Rashmi, D., Zanan, R., John, S., Khandagale, K., & Nadaf, A. (2018). γ-Aminobutyric Acid (GABA): Biosynthesis, Role, Commercial Production, and Applications. Studies in Natural Products Chemistry, 57, 413–452. https://doi.org/10.1016/B978-0-444-64057-4.00013-2
- Powers, M. E., Yarrow, J. F., Mccoy, S. C., & Borst, S. E. (2008). Growth hormone isoform responses to GABA ingestion at rest and after exercise. Medicine and Science in Sports and Exercise, 40(1), 104–110. https://doi.org/10.1249/MSS.0B013E318158B518
- Cavagnini, F., Invitti, C., Pinto, M., Maraschini, C., Di Landro, A., Dubini, A., & Marelli, A. (1980). Effect of acute and repeated administration of gamma aminobutyric acid (GABA) on growth hormone and prolactin secretion in man. Acta Endocrinologica, 93(2), 149–154. https://doi.org/10.1530/ACTA.0.0930149
- Chen, J. C., Hsiang, C. Y., Lin, Y. C., & Ho, T. Y. (2014). Deer Antler Extract Improves Fatigue Effect through Altering the Expression of Genes Related to Muscle Strength in Skeletal Muscle of Mice. Evidence-Based Complementary and Alternative Medicine : ECAM, 2014. https://doi.org/10.1155/2014/540580
- Gu, L., Mo, E., Yang, Z., Zhu, X., Fang, Z., Sun, B., Wang, C., Bao, J., & Sung, C. (2007). Expression and localization of insulin-like growth factor-I in four parts of the red deer antler. Growth Factors (Chur, Switzerland), 25(4), 264–279. https://doi.org/10.1080/08977190701773187
- Marmillo, N. A. (2018). Changes in IGF-1 Levels Post Deer Antler Velvet Supplementation. https://doi.org/10.34917/13568568
- Syrotuik, D. G., MacFadyen, K. L., Harber, V. J., & Bell, G. J. (2005). Effect of elk velvet antler supplementation on the hormonal response to acute and chronic exercise in male and female rowers. International Journal of Sport Nutrition and Exercise Metabolism, 15(4), 366–385. https://doi.org/10.1123/IJSNEM.15.4.366
- Reddy, V. B., Iuga, A. O., Shimada, S. G., LaMotte, R. H., & Lerner, E. A. (2008). Cowhage-Evoked Itch Is Mediated by a Novel Cysteine Protease: A Ligand of Protease-Activated Receptors. The Journal of Neuroscience, 28(17), 4331. https://doi.org/10.1523/JNEUROSCI.0716-08.2008
- Pulikkalpura, H., Kurup, R., Mathew, P. J., & Baby, S. (2015). Levodopa in Mucuna pruriens and its degradation. Scientific Reports 2015 5:1, 5(1), 1–9. https://doi.org/10.1038/srep11078
- Meeusen, R., Watson, P., Hasegawa, H., Roelands, B., & Piacentini, M. F. (2006). Central fatigue: the serotonin hypothesis and beyond. Sports Medicine (Auckland, N.Z.), 36(10), 881–909. https://doi.org/10.2165/00007256-200636100-00006
- Chihara, K., Kashio, Y., Kita, T., Okimura, Y., Kaji, H., Abe, H., & Fujita, T. (1986). L-dopa stimulates release of hypothalamic growth hormone-releasing hormone in humans. The Journal of Clinical Endocrinology and Metabolism, 62(3), 466–473. https://doi.org/10.1210/JCEM-62-3-466
- Peillon, F., Cesselin, F., Bression, D., Zygelman, N., Brandi, A. M., Nousbaum, A., & Mauborgne, A. (1979). In Vitro Effect of Dopamine and L-Dopa on Prolactin and Growth Hormone Release from Human Pituitary Adenomas. The Journal of Clinical Endocrinology & Metabolism, 49(5), 737–741. https://doi.org/10.1210/JCEM-49-5-737
- Boyd, A. E. I., Lebovitz, H. E., & Pfeiffer, J. B. (2010). Stimulation of Human-Growth-Hormone Secretion by L-Dopa. Http://Dx.Doi.Org/10.1056/NEJM197012242832602, 283(26), 1425–1429. https://doi.org/10.1056/NEJM197012242832602
- Alleman, R. J., Canale, R. E., McCarthy, C. G., & Bloomer, R. J. (2011). A Blend of Chlorophytum Borivilianum and Velvet Bean Increases Serum Growth Hormone in Exercise-Trained Men. Nutrition and Metabolic Insights, 4, 55. https://doi.org/10.4137/NMI.S8127
- Liu, P., Zhao, H., & Luo, Y. (2017). Anti-Aging Implications of Astragalus Membranaceus (Huangqi): A Well-Known Chinese Tonic. Aging and Disease, 8(6), 868. https://doi.org/10.14336/AD.2017.0816
- Lee, D., Lee, S. H., Lee, Y. H., Song, J., & Kim, H. (2017). Astragalus Extract Mixture HT042 Increases Longitudinal Bone Growth Rate by Upregulating Circulatory IGF-1 in Rats. Evidence-Based Complementary and Alternative Medicine, 2017. https://doi.org/10.1155/2017/6935802
- Lee, D., Kim, B. H., Lee, S. H., Cho, W. Y., Kim, Y. S., & Kim, H. (2021). Effects of Astragalus Extract Mixture HT042 on Circulating IGF-1 Level and Growth Hormone Axis in Rats. Children, 8(11). https://doi.org/10.3390/CHILDREN8110975
- Kim, C., Ha, H., Jin, S. K., Yun, T. K., Kwon, S. C., & Sie, W. P. (2003). Induction of growth hormone by the roots ofAstragalus membranaceus in pituitary cell culture. Archives of Pharmacal Research 2003 26:1, 26(1), 34–39. https://doi.org/10.1007/BF03179928
- Hayamizu, K., Oshima, I., & Nakano, M. (2020). Comprehensive Safety Assessment of l-Lysine Supplementation from Clinical Studies: A Systematic Review. The Journal of Nutrition, 150(Supplement_1), 2561S-2569S. https://doi.org/10.1093/JN/NXAA218
- Shao, A., & Hathcock, J. N. (2008). Risk assessment for the amino acids taurine, L-glutamine and L-arginine. Regulatory Toxicology and Pharmacology : RTP, 50(3), 376–399. https://doi.org/10.1016/J.YRTPH.2008.01.004
- Bucci, L., Hickson, J. F., Pivarnik, J. M., Wolinsky, I., McMahon, J. C., & Turner, S. D. (1990). Ornithine ingestion and growth hormone release in bodybuilders. Nutrition Research, 10(3), 239–245. https://doi.org/10.1016/S0271-5317(05)80265-9
- Holecek, M. (2013). Side effects of long-term glutamine supplementation. JPEN. Journal of Parenteral and Enteral Nutrition, 37(5), 607–616. https://doi.org/10.1177/0148607112460682
- Oketch-Rabah, H. A., Madden, E. F., Roe, A. L., & Betz, J. M. (2021). United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA). Nutrients, 13(8). https://doi.org/10.3390/NU13082742
- Cavagnini, F., Invitti, C., Pinto, M., Maraschini, C., Di Landro, A., Dubini, A., & Marelli, A. (1980). Effect of acute and repeated administration of gamma aminobutyric acid (GABA) on growth hormone and prolactin secretion in man. Acta Endocrinologica, 93(2), 149–154. https://doi.org/10.1530/ACTA.0.0930149
- Katzenshlager, R., Evans, A., Manson, A., Palsalos, P. N., Ratnaraj, N., Watt, H., Timmermann, L., Van Der Giessen, R., & Lees, A. J. (2004). Mucuna pruriens in Parkinson’s disease: a double blind clinical and pharmacological study. Journal of Neurology, Neurosurgery, and Psychiatry, 75(12), 1672–1677. https://doi.org/10.1136/JNNP.2003.028761
- Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: carbidopa, nausea, and dyskinesia. Clinical Pharmacology : Advances and Applications, 6, 189. https://doi.org/10.2147/CPAA.S72234
- Kazushige Goto, Naokata Ishii, Tomohiro Kizuka, & Kaoru Takamatsu. (n.d.). The impact of metabolic stress on hormonal responses and muscular adaptations - PubMed. Retrieved November 8, 2022, from https://pubmed.ncbi.nlm.nih.gov/15947720/
- Stokes, K. A., Sykes, D., Gilbert, K. L., Chen, J. W., & Frystyk, J. (2010). Brief, high intensity exercise alters serum ghrelin and growth hormone concentrations but not IGF-I, IGF-II or IGF-I bioactivity. Growth Hormone & IGF Research : Official Journal of the Growth Hormone Research Society and the International IGF Research Society, 20(4), 289–294. https://doi.org/10.1016/J.GHIR.2010.03.004
- Craig, B. W., Lucas, J., Pohlman, R., & Stelling, H. (n.d.). The Effects of Running, Weightlifting and a Combination of B... : The Journal of Strength & Conditioning Research. Retrieved November 8, 2022, from https://journals.lww.com/nsca-jscr/Abstract/1991/11000/The_Effects_of_Running,_Weightlifting_and_a.5.aspx
- Pritzlaff, C. J., Wideman, L., Weltman, J. Y., Abbott, R. D., Gutgesell, M. E., Hartman, M. L., Veldhuis, J. D., & Weltman, A. (1999). Impact of acute exercise intensity on pulsatile growth hormone release in men. Journal of Applied Physiology (Bethesda, Md. : 1985), 87(2), 498–504. https://doi.org/10.1152/JAPPL.1999.87.2.498
- Felsing, N. E., Brasel, J. A., & Cooper, D. M. (1992). Effect of low and high intensity exercise on circulating growth hormone in men. The Journal of Clinical Endocrinology and Metabolism, 75(1), 157–162. https://doi.org/10.1210/JCEM.75.1.1619005
- Veldhuis, J. D., Keenan, D. M., Bailey, J. N., Adeniji, A. M., Miles, J. M., & Bowers, C. Y. (2009). Novel Relationships of Age, Visceral Adiposity, Insulin-Like Growth Factor (IGF)-I and IGF Binding Protein Concentrations to Growth Hormone (GH) Releasing-Hormone and GH Releasing-Peptide Efficacies in Men during Experimental Hypogonadal Clamp. The Journal of Clinical Endocrinology and Metabolism, 94(6), 2137. https://doi.org/10.1210/JC.2009-0136
- Velloso, C. P. (2008). Regulation of muscle mass by growth hormone and IGF-I. British Journal of Pharmacology, 154(3), 557. https://doi.org/10.1038/BJP.2008.153
- Veldhuis, J. D., Liem, A. Y., South, S., Weltman, A., Weltman, J., Clemmons, D. A., Abbott, R., Mulligan, T., Johnson, M. L., Pincus, S., Straume, M., & Iranmanesh, A. (1995). Differential impact of age, sex steroid hormones, and obesity on basal versus pulsatile growth hormone secretion in men as assessed in an ultrasensitive chemiluminescence assay. The Journal of Clinical Endocrinology and Metabolism, 80(11), 3209–3222. https://doi.org/10.1210/JCEM.80.11.7593428
- Rasmussen, M. H., Hvidberg, A., Juul, A., Main, K. M., Gotfredsen, A., Skakkebaek, N. E., & Hilsted, J. (1995). Massive weight loss restores 24-hour growth hormone release profiles and serum insulin-like growth factor-I levels in obese subjects. The Journal of Clinical Endocrinology and Metabolism, 80(4), 1407–1415. https://doi.org/10.1210/JCEM.80.4.7536210