GHRP-2, GHRP-6 and Ipamorelin – Which to Use and Why

The following article was written by Mike Ross from Muscle Chemistry

GHRP-2

Growth-Hormone-Releasing-Peptide-Two (GHRP-2) is a synthetic Ghrelin analogue. It causes the release of endogenous (internal) Growth Hormone (GH) from somatotropes in the anterior pituitary gland. It works synergistically with GHRH’s and lacks the lipogenic properties (fat creation/storage) of Ghrelin. GHRP-2 excites the hypothalamus and causes a high release of GH which tapers back to baseline by the third hour post admin. This pulse closely represents that of the natural pulse of the human body giving it an advantage over synthetic GH use.

Benefits and Potential of GHRP-2

Similar to Ipamorelin, GHRP-2 has great benefits and potential in athletes. GHRP-2 has been studied and shown to be effective in treating age-related GH decline when used in combination with a GHRH such as CJC-1295. GHRP-2 when use with an equal dose of a GHRH creates a 3-hour pulse of GH that is double the amplitude of 8 units of synthetic GH. This makes it a more effective, healthier substitute to synthetic Growth Hormone with the added safety and lower cost benefits.

GHRP-6

Growth-Hormone-Releasing-Peptide-6 (GHRP-6) is a Growth Hormone (GH) secretagogue and Ghrelin mimetic.

The peptide GHRP-6 works similarly to GHRP-2 and Ipamorelin, however it induces hunger consistently in mammals. It also does have some lipogenic properties that are dependent on the status on insulin and glucose. GHRP-6 may cause weight and adipose tissue gain if insulin is present. So don’t eat for 30 mins post injection, nothing, nada. You’ll be starving but don’t eat.

Benefits and Potential of GHRP-6

Again, similar to GHRP-2 and Ipamorelin, GHRP-6 has many benefits and uses. Due to the increased GH release, the following benefits may be observed:

  • Increased Energy
  • Improved Sleep
  • Increased Lean Body Mass
  • Decreased Body Fat
  • Increased Collagen Production
  • Increased Healing Capability

Ipamorelin

Ipamorelin or NNC 26-0161, a polypeptide hormone, is a growth hormone secretagogue and Ghrelin mimetic and analog developed by Novo Nordisk. Ipamorelin belongs to the most recent generation of GHRP’s from the mid 1990’s and causes significant release of growth hormone by itself, due both to its suppression of somatostatin (an antagonist to GHRH) and stimulation of release of GH from the anterior pituitary, similar to GHRP-2 and GHRP-6 which are compounds from the same class (growth hormone releasing peptides). The cells that produce and release GH are known as somatotropes. Like GHRP-2, ipamorelin does not have Ghrelin’s lipogenic properties. Like GHRP-2 and unlike GHRP-6 ipamorelin never induces hunger in mammals. Ipamorelin acts synergistically when applied during a native GHRH (growth-hormone releasing hormone) pulse or when coadministered with GHRH or a GHRH analog such as Sermorelin or GRF 1-29 (growth releasing factor, aminos 1-29). The synergy comes both due to the suppression of somatostatin and the fact that ipamorelin increases GH release per-somatotrope, while GHRH increases the number of somatotropes releasing GH. There is also a secondary effect of neuronal excitation in the hypothalamus caused by ipamorelin, which lasts for approximately 3 hours after application, similar to GHRP-2 and GHRP-6.

Ipamorelin has a unique property among the GHRP class of peptides. That property is known as selectiveness. Whereas GHRP-6 and GHRP-2 cause a release and increase in cortisol and prolactin levels, ipamorelin only selectively releases GH at any dose. Further, a mega-dose of ipamorelin results in a concomitant mega-release of GH (up to the entire amount present in the pituitary), whereas GHRP-2 and GHRP-6 have limits of approximately 1mcg/kg in humans for their maximal GH release.

Which is Best?

The development and pharmacology of a new potent growth hormone (GH) secretagogue, ipamorelin, is described. Ipamorelin is a pentapeptide, which displays high GH releasing potency and efficacy in vitro and in vivo. As an outcome of a major chemistry programme, ipamorelin was identified within a series of compounds lacking the central dipeptide Ala-Trp of growth hormone-releasing peptide (GHRP)-1. In vitro, ipamorelin released GH from primary rat pituitary cells with a potency and efficacy similar to GHRP-6 (ECs) = 1.3+/-0.4nmol/l and Emax = 85+/-5% vs 2.2+/-0.3nmol/l and 100%). A pharmacological profiling using GHRP and growth hormone-releasing hormone (GHRH) antagonists clearly demonstrated that ipamorelin, like GHRP-6, stimulates GH release via a GHRP-like receptor. In pentobarbital anaesthetised rats, ipamorelin released GH with a potency and efficacy comparable to GHRP-6 (ED50 = 80+/-42nmol/kg and Emax = 1545+/-250ng GH/ml vs 115+/-36nmol/kg and 1167+/-120ng GH/ml). In conscious swine, ipamorelin released GH with an ED50 = 2.3+/-0.03 nmol/kg and an Emax = 65+/-0.2 ng GH/ml plasma. Again, this was very similar to GHRP-6 (ED50 = 3.9+/-1.4 nmol/kg and Emax = 74+/-7ng GH/ml plasma). GHRP-2 displayed higher potency but lower efficacy (ED50 = 0.6 nmol/kg and Emax = 56+/-6 ng GH/ml plasma). The specificity for GH release was studied in swine. None of the GH secretagogues tested affected FSH, LH, PRL or TSH plasma levels. Administration of both GHRP-6 and GHRP-2 resulted in increased plasma levels of ACTH and cortisol. Very surprisingly, ipamorelin did not release ACTH or cortisol in levels significantly different from those observed following GHRH stimulation. This lack of effect on ACTH and cortisol plasma levels was evident even at doses more than 200-fold higher than the ED50 for GH release. In conclusion, ipamorelin is the first GHRP-receptor agonist with a selectivity for GH release similar to that displayed by GHRH. The specificity of ipamorelin makes this compound a very interesting candidate for future clinical development.

Ipamorelin has been identified as the most effective.

Comparison Chart for GHRP’s

Name Work with GHRH Better than Synthetic GH Stimulates Hunger Stimulate Possible Fat Storage Raise ACTH, Cortisol, Prolactin Levels
GHRP- 2 Yes Yes No No Yes
GHRP-6 Yes Yes Yes Yes Yes
Ipamorelin Yes Yes No No No

All GHRP’s Have the Following Benefits:

  • Increased energy
  • Improved sleep and mood
  • Increased lean muscle mass
  • Decreased body fat
  • Increased healing ability
  • Increased collagen production
  • No marked effect on FSH, LH, or TSH plasma levels

For best results use with GHRH’s such as CJC-1295.

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