For bodybuilders and fitness enthusiasts, nothing is more important than optimal muscle growth (except for rapid fat loss).
But progress doesn’t always come quickly — it requires a fully optimized lifestyle made up of rigorous meal planning and strict intelligent training.
That’s why many of them are seeking out growth hormone-releasing peptides (GHRPs) to achieve their muscle-building goals faster without any deleterious side effects.
These synthetic peptides primarily work by naturally stimulating the release of growth hormone.
This consequently leads to enhanced muscle development, better recovery, increased strength, and improved physical performance.
Most importantly, all of these outcomes can be achieved without compromising their health or the integrity of their hard-earned physique.
In this article, we’ll discuss the benefits of GHRPs, how they can help you achieve your physique-building goals, and what people consider to be the top picks for promoting muscle growth.
How Peptides Promote Muscle Growth
Peptides are strings of 2-100 molecules called amino acids that are linked by peptide bonds.
They have structures similar to some messaging compounds and hormones in the body, helping activate and engage with the body’s receptors to influence important bodily processes.
Thus, your body produces peptides that play an important role in many bodily functions, one of them being the development of lean muscle tissue.
Peptides primarily support muscle growth through 4 mechanisms: (1) boosting protein synthesis, (2) improving recovery, (3) minimizing oxidative stress and inflammation, and (4) increasing nutrient absorption.
This makes them a viable alternative to steroids as they work with your body’s natural processes while possessing far fewer health risks.
(NOTE: You can read more about the differences between peptides and steroids here)
For instance, there’s a class of muscle-building peptides called growth hormone secretagogues (GHS).
Through the promotion of human growth hormone (HGH) release, the result is better muscle growth, physical performance, body fat loss, and recovery.
What are Growth Hormone-Releasing Peptides (GHRPs)?
Growth hormone-releasing peptides, also called GHRPs, are synthetic substances that stimulate the release of growth hormone from the hypothalamus and pituitary gland.
Some of the most widely recognized GHRPs include Alexamorelin, GHRP-1, GHRP-2, GHRP-3, GHRP-4, GHRP-5, GHRP-6, and Hexarelin.
These peptides function as powerful messengers for regeneration and repair within the body due to the increased growth hormone secretion.
When growth hormone levels are maintained, your body can efficiently repair body tissue and recover more quickly from acute damage.
On the other hand, when growth hormone levels decline, the body struggles with regeneration and repair, leading to slower recovery and diminished vitality.
Once you reach your 50s, your growth hormone levels are seriously low, which can result in any of the following health symptoms:
- Loss of muscle mass
- Low energy
- Brain fog
- Slow recovery time after physical activity
- Hair loss
- Low libido
- Poor quality of sleep
- Higher body fat concentrated around the waist
- Problems with sexual function
- Decreased overall strength and endurance
GHRPs counteract this natural decline by replacing the hormones that are no longer sufficiently produced by the body naturally.
Once injected, GHRPs trigger your pituitary gland to produce and release greater amounts of HGH.
In turn, this stimulates your liver to release insulin-like growth factor-1 (IGF-1), thereby promoting muscle protein production and muscle growth.
If you’re looking to use GHRPs to promote muscle growth and HGH production, below are the top 3 most popular choices.
The 3 Best GHRPs to Stimulate Muscle Growth and HGH Production
Here are the three most effective GHRPs for anyone seeking increased growth hormone production.
GHRP-2
GHRP-2, also known as KP-102, is a synthetic hexapeptide classified as a growth hormone-releasing peptide (GHRP).
This powerful compound targets the hypothalamus and pituitary gland to trigger the release of human growth hormone (HGH).
It also exerts a mild stimulating effect on the levels of prolactin, adrenocorticotropic hormone (ACTH), and cortisol.
Because GHRP-2 encourages the body’s natural production of (HGH), it helps increase lean muscle mass while reducing body fat.
And what makes GHRP-2 stand out is that it can achieve peak concentrations within 15 minutes of administration and these levels are maintained for up to an hour.
This happens because of GHRP-2’s ability to boost insulin-like growth factor-1 (IGF-1) levels, especially when combined with a growth hormone-releasing hormone (GHRH).
(NOTE: Adding in a GHRH alongside a GHRP enhances the overall effectiveness of both peptides as they work synergistically to elevate HGH production and secretion)
One study in yaks demonstrated improved skeletal muscle and muscle protein deposition after taking GHRP-2:
“Trial 1, thirty-six 1-year-old Qinghai high plateau yaks (body weight 38–83.2 kg) were randomly chosen for body weight and jugular blood samples collection.
The relationship between body weight and serum GHRH (P < 0.05, R = 0.45), GH (P < 0.05, R = 0.47), IGF-1 (P < 0.05, R = 0.62) was significantly correlated in yaks colonies with lighter body weights.
Trial 2, fifteen 1-year-old Qinghai high plateau yaks with growth retardation (average body weight 54.8 ± 8.24 kg) were randomly selected and assigned to negative control group (NG), GHRP-2 injection group (GG) and cysteamine feeding group (CG), with 5 yaks per group.
Another five 1-year-old Qinghai high plateau yaks with normal growth performance (average body weight 75.3 ± 2.43 kg) were selected as positive control group (PG).
The average daily gain (ADG) of the GG and CG were significantly higher than those in the PG and NG (P < 0.05).
Both GHRP-2 and CS administration significantly enhanced the myofiber diameter and area of skeletal muscle (P<0.05).
GHRP-2 significantly enhanced the serum GH and IGF-1 levels (P < 0.05), and up-regulated GHR, IGF-1 and IGF-1R mRNA expression in the liver and skeletal muscle (P < 0.05), enhanced the mRNA expression of PI3K, AKt and mTOR in the skeletal muscle (P<0.05).
CS significantly reduced the serum SS levels and the hypothalamus SS mRNA expression (P < 0.05), and enhanced GHR and IGF-1 mRNA expression in the liver (P < 0.05), decreased the mRNA expression of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1) mRNA (P < 0.05).”
GHRP-6
GHRP-6 is thought by many to be one of the top peptides for boosting muscle growth.
This hexapeptide enhances the production of HGH and stimulates appetite by working with your body’s natural growth processes.
GHRP-6 is known for its ability to support the building of lean muscle mass and assist in fat burning.
Like GHRP-2, GHRP-6 works by stimulating the anterior pituitary gland to increase the production of HGH levels, which prompts the liver to secrete IGF-1.
Moreover, GHRP-6 directly affects the feedback loop that controls growth hormone release, allowing for the re-stimulation of growth hormone production.
Obviously, this leads to sustained muscle growth and fat loss over time.
But most notably it increases hunger, which is especially useful during bulking phases for trainees who struggle to consistently eat at a caloric surplus.
A study published in the Journal of BMB Reports showed that GHRP-6 helps increase expression levels of IGF-1 and collagen type I.
As you already know, IGF-1 helps boost muscle growth, regeneration, and muscle hypertrophy when training.
Whereas collagen type 1 helps promote glycine production, helping grow muscles:
“Based on the potential beneficial effects of growth hormone-releasing peptide (GHRP)-6 on muscle functions, a newly synthesized GHRP-6-biotin conjugate was tested on cultured myoblast cells.
Increased expression of myogenic marker proteins was observed in GHRP-6-biotin conjugate-treated cells.
Additionally, increased expression levels of insulin-like growth factor-1 and collagen type I were observed.
Furthermore, GHRP-6-biotin conjugate-treated cells showed increased metabolic activity, as indicated by increased concentrations of energy metabolites, such as ATP and lactate, and increased enzymatic activity of lactate dehydrogenase and creatine kinase.
Finally, binding protein analysis suggested a few candidate proteins, including desmin, actin, and zinc finger protein 691 as potential targets for GHRP6-biotin conjugate action.
These results suggest that the newly synthesized GHRP-6-biotin conjugate has myogenic stimulating activity through, at least in part, by stimulating collagen type I synthesis and several key proteins.
Practical applications of the GHRP-6-biotin conjugate could include improving muscle condition.”
Hexarelin
Hexarelin a synthetic hexapeptide developed by Mediolanum Farmaceutici in Milan, Italy in 1972.
It resembles GHRP-6 in both function and structure, yet it doesn’t increase your appetite.
This makes it ideal for fat loss programs involving the consumption of fewer calories/carbohydrates.
Hexarelin belongs to the growth hormone secretagogue classs, and like the other two GHRPs it works primarily through the release of HGH from the anterior pituitary gland.
It binds with the growth hormone secretagogue receptor located in the hippocampus and activates a phospholipid-dependent protein kinase (PKC) signaling pathway that boosts HGH release.
As a result, it helps regulate body weight and support musculoskeletal system development.
Hexarelin also minimizes somatostatin release, further amplifying HGH synthesis and release.
The end result is improved amino acid recruitment and protein synthesis in the muscle fibers, which is beneficial muscle growth and strength.
The increased HGH levels also encourage nitrogen retention, resulting in new muscle cell growth and the preservation of existing muscle cells.
Finally, Hexarelin promotes the growth and development of new muscle fibers, which develop lean muscle mass via improved muscle size and overall bodily strength.
In a study in The Journals of Gerontology, the administration of Hexarelin to six old beagle dogs improved their morphological and biochemical muscular indices after 16 weeks:
“Hexarelin was administered for 16 weeks to six old beagle dogs.
The treatment consisted of three on-drug periods spaced by two off-drug periods.
During each period, the growth hormone (GH) peak response to HEXA initially increased and then dropped to pretreatment values.
Each time, a wash-out interval restored the same pattern of responsiveness.
HEXA significantly augmented the indices of spontaneous pulsatility of GH, but plasma insulin-like growth factor I levels did not change during treatment.
HEXA reduced bone resorption since it significantly decreased the urinary concentration of lysylpyridinoline, a bone matrix component.
Bone formation was not affected since unchanged levels of alkaline phosphatase were recorded.
In three of six old dogs, HEXA induced an improvement of some morphological and biochemical muscular indices, evaluated in muscle specimens that, instead, remained unchanged in a group of young untreated controls.
These findings indicate that HEXA effectively releases GH and primes the pituitary of old dogs and strengthen the view that in aging, GH secretion may be restored by pharmacological means. It would also appear that HEXA-induced GH release improves some indices of body composition in old dogs.”
Therapeutic Benefits of GHRPs
Aside from muscle growth, GHRPs also offer other health benefits.
Stimulation of Growth Hormone Secretion
As you’ve gathered by now, GHRPs promote the release of HGH through the pituitary gland.
For this reason alone, they have become highly popular in athletic and bodybuilding communities as performance-enhancing anabolic compounds.
A deficiency in GH can result in reduced muscle strength and mass, but this can be effectively reversed with the use of GHRPs.
This was observed when Brazilian researchers worked with men over 50 years old to determine how HGH therapy could help improve their muscle strength.
After 6 months of HGH therapy, participants who completed the trial showed improvement in their leg press strength compared to when they started:
“Fourteen healthy men aged 50–70 years were evaluated at baseline for body composition and muscle strength (evaluated by leg press and bench press exercises, which focus primarily on quadriceps—lower body part and pectoralis major—upper body part—muscles, resp.).
Subjects were randomised into 2 groups: GH therapy (7 subjects) and placebo (7 subjects) and reevaluated after 6 months of therapy.
Thirteen subjects completed the study (6 subjects in the placebo group and 7 subjects in the GH group).
Subjects of both groups were not different at baseline. After 6 months of therapy, muscle strength in the bench press responsive muscles did not increase in both groups and showed a statistically significant increase in the leg press responsive muscles in the GH group.
Our study demonstrated an increase in muscle strength in the lower body part after GH therapy in healthy men.”
Cytoprotective Effects
GHRPs offer cytoprotective effects by preventing necrosis and apoptosis and reducing inflammation.
They do so by binding with the receptors GHS-R1a and CD36 and triggering a series of biological cascades
For example, GHRPs that bind to CD36 activate PI-3K/AKT1 and prosurvival pathways.
This leads to minimized cellular death, reduced reactive oxygen species (ROS) spillover, improved antioxidant defenses, and lower inflammation.
These cytoprotective abilities of GHRPs have been proven effective for neuronal, cardiac, neuronal, hepatic, and gastrointestinal cell health.
For example, researchers have discovered that GHRP-6 can help lessen the severity of liver damage caused by ischemia-reperfusion (I/R) injury.
It can also help improve respiratory distress syndrome, acute tubular necrosis in kidneys, and intestinal transmural infarction:
“Years ago, our group examined the cytoprotective effects exerted by the GHRP-6 preventive administration in the hepatic tissue subjected to I/R, as in other distal organs from the ischemic site (ie, lungs, kidneys, and small intestine).
Histological and biochemical results allowed us to conclude that the pharmacological preconditioning induced by the GHRP-6 treatment attenuated I/R liver damage.
Besides respiratory distress syndrome like pulmonary changes, intestinal transmural infarction and acute tubular necrosis in kidneys were significantly reduced.
These results indicated for the first time a systemic cytoprotective effect for the GHRP-6, suggesting its potential efficacy to control the inflammatory response associated with acute I/R and shock, which eventually caused multiple organ damage (MOD).
Cytoprotection induced by GHRP-6 treatment was also related to the attenuation in the generation of ROS and preservation of the antioxidant defense reserves.
Histological analysis as the assessment of myeloperoxidase activity evidenced a clear anti-inflammatory GHRP-6-induced effect in the liver and remote organs.
Moreover, the molecular mechanism mediating the action of GHRP-6 peptide was shown to involve the phosphatidylinositol 3-kinase/RAC-alpha serine/threonine-protein kinase (PI-3K/AKT1) pathway, as the induction of the hypoxia-inducible factor-1 alpha (HIF-1α) all committed in cellular survival.”
Metabolic Regulation
Excess body weight is one of the major risk factors for metabolic disorders, including obesity and type 2 diabetes.
Fortunately, HGH helps regulate carbohydrate and lipid metabolism by interacting with insulin and IGF-1, therefore promoting weight loss.
Within the literature, a study in The Journal of Clinical Endocrinology & Metabolism was done on 122 men who were also using testosterone.
The findings suggest that HGH supplementation can also reduce body and trunk fat:
“One hundred twenty-two community-dwelling men 70.8 ± 4.2 yr of age with body mass index of 27.4 ± 3.4 kg/m2, testosterone of 550 ng/dl or less, and IGF-I in lower adult tertile were randomized to receive transdermal testosterone (5 or 10 g/d) during a Leydig cell clamp plus GH (0, 3, or 5 μg/kg · d) for 16 wk.
Body composition by dual-energy x-ray absorptiometry, muscle performance, and safety tests were conducted.
Total lean body mass increased (1.0 ± 1.7 to 3.0 ± 2.2 kg) as did appendicular lean tissue (0.4 ± 1.4 to 1.5 ± 1.3 kg), whereas total fat mass decreased by 0.4 ± 0.9 to 2.3 ± 1.7 kg as did trunk fat (0.5 ± 0.9 to 1.5 ± 1.0 kg) across the six treatment groups and by dose levels for each parameter (P ≤ 0.0004 for linear trend).
Composite maximum voluntary strength of upper and lower body muscles increased by 14 ± 34 to 35 ± 31% (P < 0.003 in the three highest dose groups) that correlated with changes in appendicular lean mass.
Aerobic endurance increased in all six groups (average 96 ± 137sec longer). Systolic and diastolic blood pressure increased similarly in each group with mean increases of 12 ± 14 and 8 ± 8 mm Hg, respectively. Other predictable adverse events were modest and reversible.”
Anti-Fibrotic Effects
GHRPs not only promote muscle growth and upregulated metabolism, but can also exhibit anti-fibrotic effects.
They can help reduce or prevent the formation of excess fibrous connective tissue, which minimizes scarring and improves organ function.
They do this by reducing inflammation, inhibiting fibroblast activation, promoting tissue repair, and modulating fibrogenic pathways.
This makes GHRPs potential therapeutic agents for treating various fibrotic diseases (ex. liver, pulmonary, cardio, kidney fibrosis), leading to better organ function and overall health.
Cuban researchers discovered that chronic treatment with GHRP-6 for 21 days prevented sudden death in dogs with dilated cardiomyopathy (DCM) and heart attacks.
While they aren’t sure why this happened, they believe that GHRP-6 improved heart function in the areas not affected by the heart attacks:
“Our group has contributed to validating the potential antifibrotic abilities of GHRP-6 in animal models of liver cirrhosis and hypertrophic scars in which via a peroxisomal proliferator-activated receptor gamma (PPARγ)-driven cascade, GHRP-6 intervention reduced TGF-β1 and connective tissue growth factor (CTGF) expression, which translated in a dramatic reduction in the accumulation of collagen and other extracellular matrix (ECM) proteins.
A seminal report by a Merck Research Laboratories group dated 2003 demonstrated for the first time that chronic treatment with GHRP-6 (21 days) prevented sudden death in a canine model of DCM and subsequently subjected to acute myocardial infarction (AMI).
In the meantime, the mortality rates for the vehicle and GH-treated groups were about 50%.
Although the authors do not precise the mechanism underlying the 100% survival in the GHRP-6 group, an enhanced regional myocardial compensatory function of the nonischemic zone was assumed.
This notion could be validated at least in part by the fact that the cardiotropic effects shown by GHRP-1, GHRP-2, GHRP-6, and hexarelin in cardiomyocytes and isolated, denervated, perfused hearts are mediated by an elevation of Ca2+ influx through the voltage-gated calcium channel, triggering Ca2+ release from thapsigargin-sensitive intracellular stores, which translated in a positive inotropic response without a chronotropic effect.”
Potential in Hypogonadism Management
Male hypogonadism affects approximately 4 million men in the United States.
Although it can occur at any age, 60% of men over the age of 65 have free testosterone levels lower than the normal range of men in their 30s.
Obesity and metabolic syndrome have a two-way relationship with hypogonadism, i.e. they can both cause hypogonadism and be the end result of hypogonadism.
Some researchers are looking into growth hormone secretagogues (GHS) as a promising new alternative therapy to testosterone for treating hypogonadism.
In their mind, GHSs can improve body composition in a way that is independent of the androgen-dependent gonadal axis.
A study published in the American Journal of Men’s Health found that hypogonadal men treated with GHRPs saw improved IGF-1, testosterone, and free testosterone levels:
“Fourteen hypogonadal men on T therapy with baseline IGF-1 levels <200 ng/mL were treated with GHRP-6, GHRP-2, and SERM three times daily at a dose of 100 mcg of each compound delivered via subcutaneous injection.
Mean (SD) age within the cohort was 33.2 (2.9; range 29–39) years. Baseline mean (SD) hormone levels were IGF-1 159.5 (26.7; range 97–195) ng/mL, T 586.9 (550.5; range 76–1640) ng/dL, FT 12.9 (11.8; range 2.2–36.7) ng/dL, FSH 1.1 (1.9; range 0.02–7) mIU/mL, LH 1.1 (1.4; range 0.02–4) mIU/mL, and E 5.5 (9.0; range 2–38) ng/dL.
Mean (SD) duration of GHRP-6/GHRP-2/SERM treatment was 134 (88) days. Significant increases in IGF-1 levels were observed at all follow-up intervals.
Significant increases in T and FT levels were also observed starting at 90 days of follow-up. No significant changes in LH, FSH, or E levels were observed at any point during follow-up.”
Potential Side Effects of Using Peptides for Muscle Growth
Clearly, the use of peptides can help boost your muscle growth and achieve your desired gains.
The problem is that improper use or abuse of GHRPs can result in side effects and serious health conditions such as:
- Nausea
- Headaches
- Fluid retention
- Increased hunger
- Vomiting
- Motor paralysis
- Diabetes
- Hypothyroidism
- Hypertension
- Osteoporosis
- Motor paralysis
- Skeletal muscle damage and loss
Fortunately, as long as you use the proper dosage and administration, along with living insulin-controlled, you have nothing to worry about.
Jay’s Closing Thoughts
Although I AM aware of the popularity of all the peptides featured in this article (which is why they even get any sort of mention), they are ultimately worthless.
The only GHRP worth using is Ipamorelin and I very clearly spell out why in my definitive guide to using HGH:
“At this time, Ipamorelin is the only one I can recommend as it SELECTIVELY stimulates the release of hGH without affecting luteinizing hormone (LH), follicle-stimulating hormone (FSH), or thyroid-stimulating hormone (TSH), prolactin, and cortisol.
Inadvertently elevating these bodily hormones can lead to unwanted side effects such as weakened immunity and elevated blood pressure.
…The same selectivity is not observed in other GHRPs”
Until the pharmaceutical companies or a genius chemist in his underground laboratory develops a superior GHRP, you effectively only have one choice if you want to see serious results.
Which is fantastic news considering it’s time and money you don’t have to waste testing all the other GHRPs to “see which one works best for you.”
But of course… if you read the HGH article, you’ll know that pharma-grade HGH is not only superior to Ipamorelin but any combination of a GHRP and GHRH for that matter.
Key Takeaways and Where to Source the Best Peptides for Muscle Growth
If you’re looking to bulk up and achieve your desired muscle gains, GHRPs are promising tools to promote muscle growth.
They are effective in promoting the natural release of HGH, thus improving muscle mass and strength while simultaneously accelerating fat loss.
However, not all GHRPs are created equal, so make sure you are procuring your peptides from trusted sources like Limitless Life Nootropics because they are the biohacking industry’s only reliable vendor for 3rd-party tested research products.
They have the best research formulation of GHRPs like Ipamorelin available and no other vendor comes close to offering them at ultra-high levels of purity for reasonable prices.
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But before you start injecting these peptides into your body recklessly, make sure you first read the Top 10 Mistakes People Make When Starting Therapeutic Peptides FREE PDF!
Seriously, this short e-book will save you a lot of wasted money and poorly spent time (not to mention preventing you from potential self-inflicted missteps).
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