GHRP-6 (Growth Hormone Releasing Hexapeptide 6)
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Chemical Name |
L-histidyl-D-tryptophyl-L-alanyl-L-tryptophyl-D-phenylalanyl-L-Lysinamide |
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Molecular Weight |
873.014 g/mol |
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Formula |
C46H56N12O6 |
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Half Life |
15 – 60minutes |
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Overview and history of GHRP-6
GHRP-6 (growth hormone-releasing hexapeptide 6) is a peptide hormone (also known as a protein hormone) that belongs to a category known as human growth hormone (HGH) secretagogues.
In other words, this peptide hormone works in the body by stimulating the secretion of human growth hormone.
GHRP-6 also belongs to a category of HGH secretagogues known as ghrelin mimetics, which are various growth hormone-releasing hexapeptide analogs.
Peptides in this family include GHRP-6, GHRP-2, hexarelin, and ipamorelin.
They are called ghrelin mimetics because they mimic the actions of the endogenous hormone ghrelin and attach to GH-secreting receptors in the anterior pituitary [1].
Other activities of ghrelin include its activity as a hunger-stimulating peptide hormone, which easily explains the ability of many GHRPs to stimulate appetite to varying degrees.
It is very important to note that GHRP-6, as well as the other aforementioned ghrelin mimetics, is a peptide hormone that is very distinctly different from growth hormone releasing hormone (GHRH) (e.g. Mod GRF 1-29 (CJC-1295 without DAC)).
GHRH peptides like Mod GRF -129 and GHRP peptides like GHRP-6 are very different classes of GH secretagogues that act through very different receptors and pathways.
Therefore, the two should not be confused with each other.
GHRP-6 is a first-generation GHRP and, like all other HGH secretagogues, is a very new compound that is currently undergoing clinical trials.
As such, the extent of knowledge currently gathered about this peptide is very minimal, but the medical community and scientists are hopeful that research over the next few years will lead to a better understanding of this peptide.
There are many aspects of GHRP-6 and other HGH secretagogues that are not yet fully or completely understood, and this should be made clear before delving deeper into this profile.
New discoveries regarding these peptides will be made in the coming years, not only in clinical settings, but also in anecdotal settings.
Therefore, it is important for the bodybuilding and performance-enhancing drug-using community to develop a logical and rational approach to their use that is supported by appropriate clinical and scientific data wherever possible.
GHRPs work through the same pathway as other GHRPs such as GHRP-2 and Ipamorelin, but there are some distinct differences.
While almost all GHRPs stimulate hunger simply by the fact that they are ghrelin mimetics, GHRP-6 has been clinically and anecdotally proven to stimulate the greatest increase in hunger compared to all other GHRPs [2].
Research on GHRP-6 has shown that it exhibits lipogenic (fat-storing) properties when administered after a recent food intake [3].
The same study also demonstrated a significant difference in HGH secretion from the pituitary gland when administered in combination with a GHRH analog (77% increase in HGH secretion) compared to when administered alone.
Eating carbohydrates and fats too quickly before or after GHRP-6 (or any GHRP) administration has been shown to slow the release of HGH from the pituitary gland [4].
The aforementioned study also demonstrated that the presence of acetylcholine in the brain amplifies the amount of HGH released through its inhibitory effect on somatostatin (a hormone that inhibits HGH release from the pituitary gland).
Additionally, this peptide (like GHRP-2) has demonstrated the ability to increase cortisol and prolactin secretion along with HGH secretion, although secretion levels of these two hormones are only known to be problematic in the high dose range [5].
Insulin has also been shown in studies to amplify the HGH response to GHRP-6 [6].
What does all of this mean for GHRP-6 and how can it be used?
We'll discuss this in more detail in the GHRP-6 dosage section of this profile, but in the meantime, we can summarize a few key points:
- GHRP-6 should be administered at the right time, before or after a meal, to maximize the release of HGH from the pituitary gland.
- Ghrelin mimetics like GHRP-6 should be stacked with GHRH (e.g. Mod GRF 1-29) to initiate and amplify a greater amount of HGH in the pituitary gland compared to GHRP-6 alone.
The effects of GHRH analogs and GHRPs are synergistic in their effects on the pituitary gland in amplifying the release of HGH from the pituitary gland.
- GHRP-6 causes a less significant increase in cortisol and prolactin levels than GHRP-2, but a very slight increase as demonstrated in a study [7].
This is discussed in more detail in the GHRP-6 dosage section of this profile.
Chemical Properties of GHRP-6
GHRP-6 is a protein/peptide hormone that consists of a polypeptide chain of six amino acids.
This polypeptide chain that makes up GHRP-6 contains a non-natural D-amino acid that has been synthetically created specifically to release human growth hormone from the pituitary gland, making GHRP-6 a “true” HGH secretagogue.
GHRP-6, like all other GHRPs, interacts with receptors in the pituitary gland[8] [9] [10] (and in many cases the hypothalamus[11] [12]), which are distinctly different receptors than those that interact with GHRH.
GHRP-6 stimulates the HGH secretagogue receptor (recently renamed the ghrelin receptor), not the GHRH receptor.
Through this interaction, GHRP-6 stimulates a pulsatile release of HGH from the pituitary gland, which is most intense within the first 30 minutes and lasts for several hours (the actual half-life is between 15 and 60 minutes) [13].
Characteristics of GHRP-6
Because GHRP stimulates the secretion and release of HGH from the pituitary gland in a pulsatile manner, the effects from GHRP-6 are very similar to those expected from synthetic human growth hormone administration over a long period of time (see our human growth hormone profile here), but the time that the released human growth hormone circulates is much less than that of synthetic human growth hormone.
Human growth hormone levels only remain elevated for a few hours, and the largest amount of human growth hormone is released within the first 30 minutes after administration.
This is why it is recommended to administer GHRP multiple times throughout the day to maintain consistent and regularly high HGH levels.
Reduced body fat, increased muscle mass, increased strength, increased stamina, faster healing, improved sleep quality, and an overall sense of well-being and health are some of the common effects of HGH that can be experienced while using GHRP-6.
GHRP-6 References
[1] Growth Hormone Releasing Peptide: Clinical and Basic Aspects. Argente J, Garcia-Segura LM, Pozo J, Chowen JA. 1996;46(4-5):155-9.
[2] Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers. Lawrence CB, Snape AC, Beaudoin FM, Luckman SM. Endocrinology. 2002 Jan;143(1):155-62.
[3] Effects of growth hormone (GH)-releasing hormone (GHRH), atropine, pyridostigmine, or hypoglycemia on GH secretion induced by GHRP-6 in humans. Peñalva A, Carballo A, Pombo M, Casanueva FF, Dieguez C. J Clin Endocrinol Metab. 1993 Jan;76(1):168-71.
[4] Growth hormone-releasing peptide and its analogs. Camanni F, Ghigo E, Arvat E. Front Neuroendocrinol. 1998 Jan;19(1):47-72.
[5] Ipamorelin, the first selective growth hormone secretagogue. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Eur J Endocrinol. 1998 Nov;139(5):552-61.
[6] Ghrelin - a hormone with multiple functions. Korbonits M, Goldstone AP, Gueorguiev M, Grossman AB (2004). Frontiers in Neuroendocrinology 25 (1): 27–68. doi:10.1016/j.yfrne.2004.03.002.
[7] Human fetal pituitary expresses a functional growth hormone-releasing peptide receptor. Ilan Simon, Xinmin Yan, Shlomo Melmed. JCEM 1998 83: 174-178; doi:10.1210/jc.83.1.174.
[8] On the in vitro and in vivo activity of a novel synthetic hexapeptide that acts on the pituitary gland to specifically release growth hormone. Bowers CY, Momani FA, Reynolds GA, Hong A. 1984 Endocrinology. 114:1537-1545.
[9] Effect of a new synthetic hexapeptide on the selective stimulation of growth hormone secretion in healthy human subjects. Ilson BE, Zorkarski DK, Kernow RT, Stott RM. 1989 J Clin Endocrinol Metab. 69:212-214.
[10] On the action of growth hormone-releasing hexapeptide, GHRP. Bowers CY, Sartor AO, Reynolds GA, Badger TM. 1991 Endocrinology. 128:2027-2035.
[11] Blockade of GH secretion by growth hormone-releasing peptide (GHRP-6) and absence of synergistic action of GHRP-6 and GH-releasing hormone in patients with hypothalamic-pituitary disconnection: evidence that GHRP-6 major action is exerted at the hypothalamic level. V Popovic, S Damjanovic, D Michić, M Jurjovic, C Díguez, F Casanueva. JCEM 1995 80: 942-7; doi:10.1210/jc.80.3.942.
[12] Systemic administration of growth hormone-releasing peptide activates hypothalamic arcuate neurons. Dixon SL, Leng G, Robinson ICAF. 1993 Neurosci Lett. 53:303-306.
[13] Pharmacokinetic study of growth hormone releasing peptide 6 (GHRP-6) in nine healthy male volunteers. Cabrales A, Gil J, Fernández E, Valenzuela C, Hernández F, García I, Hernández A, Besada V, Reyes O, Padrón G, Berlanga J, Guillén G, González LJ. 2013 Jan 23;48(1-2):40-6. doi: 10.1016/j.ejps.2012.10.006. Epub 2012 Oct 23.
