GHRP-6 (Growth Hormone Releasing Hexapeptide 6)
Chemical Name:
Molecular Weight:
873.014 g/mol
Half Life:
15 – 60 minutes

Overview and History of GHRP-6

GHRP-6 (Growth Hormone Releasing Hexapeptide 6) is a peptide hormone (also referred to as a protein hormone) that belongs to a category known as HGH (Human Growth Hormone) secretagogues. That is to say that these peptide hormones will act in such a way in the body so as to stimulate secretion of Human Growth Hormone. Furthermore, GHRP-6 is a member of a category of HGH secretagogues known as Ghrelin mimetics, which are all various Growth Hormone Releasing Hexapeptide analogues. The peptides in this family include: GHRP-6, GHRP-2, Hexarelin, and Ipamorelin. They are referred to as Ghrelin mimetics because they mimic the actions of the endogenous hormone Ghrelin, whereby they will attach to the GH secretagogue receptor at the anterior pituitary gland[1]. Other activities of Ghrelin involve its activity as a hunger-stimulating peptide hormone, which easily explains the ability for many of the GHRPs to stimulate appetite to various degrees. It is very important to note that GHRP-6, as well as the other Ghrelin mimetics previously mentioned are very distinctly different peptide hormones from Growth Hormone Releasing Hormones (GHRH), such as Mod GRF 1-29 (CJC-1295 without DAC). GHRH peptides such as Mod GRF -129, and GHRP peptides such as GHRP-6, are very different classes of GH secretagogues that function through very different receptors and pathways. Therefore, the two should not be confused with one another.

GHRP-6 is a first generation GHRP, and like all other HGH secretagogues, it is a very new compound that is currently undergoing clinical trials. Therefore, the extent of gathered knowledge on this peptide is currently very minimal, but the medical establishment and its scientists are hopeful of holding a better understanding of these peptides over the next several years of research. There are many aspects of GHRP-6 and other HGH secretagogues that are not fully or completely understood, and this point must be made absolutely clear prior to delving further into this profile. New discoveries in regards to these peptides will no doubt be made over the coming years, in both clinical as well as anecdotal settings. It is the bodybuilding and performance enhancing drug using community to therefore develop logical and rational approaches to its use, supported as much as possible by proper clinical and scientific data (whenever possible).

GHRP operates via the same pathways as other GHRPs, such as GHRP-2 and Ipamorelin with some distinct differences. Almost all GHRPs will stimulate hunger simply by virtue of the fact that they are Ghrelin mimetics, but GHRP-6 has demonstrated both anecdotally as well as clinically to stimulate the largest hunger increases in comparison to all other GHRPs[2]. Studies on GHRP-6 have also demonstrated, when administered after the recent consumption of food, will exhibit lipogenic (fat-storing) properties[3]. The same study had also demonstrated the vast difference in HGH output from the pituitary gland when combined with a GHRH analogue (a 77% increase in HGH output) compared to administration alone. The consumption of carbohydrates and fats too soon before or after administration of GHRP-6 (or any GHRP) has been shown to blunt HGH release from the pituitary gland as well[4]. The aforementioned study has also demonstrated that the presence of acetylcholine in the brain will amplify the amount of HGH released via its inhibitory effects on somatostatin (a hormone that inhibits HGH release from the pituitary gland). In addition, this peptide (as well as GHRP-2) has demonstrated the ability to increase Cortisol and Prolactin secretion alongside HGH secretion, although the level of secretion of these two hormones are said to only become a concern in the higher dose ranges[5]. Insulin has demonstrated in studies to amplify the HGH response to GHRP-6 as well[6].

What does all of this mean for GHRP-6 and how it can be used? This will be further explained in the GHRP-6 doses section of this profile, but in the meantime, a few key points can be summarized:

– Proper timing of GHRP-6 doses surrounding meals should be executed so as to ensure maximal HGH release from the pituitary gland.

– GHRP Ghrelin mimetics, such as GHRP-6, should be administered in combination with a GHRH (such as Mod GRF 1-29) in order to initiate and amplify a greater pulse of HGH from the pituitary compared to GHRP-6 used solitarily on its own. The effects of a GHRH analogue with a GHRP are synergistic in their effects on the pituitary gland in amplifying the release of HGH from the pituitary.

– GHRP-6 will elevate Cortisol and Prolactin levels less significantly than GHRP-2, but does so very minimally as evidenced by studies[7]. More on this will be explained in the GHRP-6 doses section of this profile.

Chemical Characteristics of GHRP-6

GHRP-6 is a protein/peptide hormone consisting of a polypeptide chain of 6 amino acids. This polypeptide chain that makes up GHRP-6 contains unnatural D-amino acids, which were created synthetically specifically for the application of Human Growth Hormone release from the pituitary gland, making GHRP-6 known as a “true” HGH secretagogue. GHRP-6, as well as all other GHRPs, will interact with receptors on the pituitary gland[8] [9] [10] (and in many extents, on the hypothalamus as well[11] [12]) that are distinctly different receptors from the ones that GHRH interacts with. GHRP-6 will stimulate the HGH secretagogue receptor (recently renamed as the Ghrelin receptor), not the GHRH receptor. Through this interaction, GHRP-6 will stimulate a pulsatile release of HGH from the pituitary gland, which is most intense within the first 30 minutes, and lasts several hours (with the actual half-life of GHRP-6 itself being between 15 to 60 minutes)[13].

Properties of GHRP-6

Because GHRP stimulates the secretion and release of HGH from the pituitary gland in a pulsatile manner, the effects resulting from GHRP-6 are very similar from what would be expected from synthetic HGH administration over the long term (see the Human Growth Hormone profile here), although the amount of time that the released human growth hormone will remain in circulation is of a far less amount of time than synthetic Human Growth Hormone does. HGH levels will only remain raised for several hours, with the most significant amounts of HGH release only occurring within the first 30 minutes of administration. It is because of this that multiple administrations of GHRP are recommended throughout the day in order to maintain steady and/or high HGH levels on a consistent and regular basis.

Typical effects of HGH would be experienced throughout use of GHRP-6: body fat reduction, muscle mass increases, strength increases, stamina increases, and increased rate of healing, sleep quality improvement, and general increased well-being and health.




GHRP-6 References:

[1] Growth hormone-releasing peptides: clinical and basic aspects. Argente J, García-Segura LM, Pozo J, Chowen JA. Horm Res. 1996;46(4-5):155-9.

[2] Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers. Lawrence CB, Snape AC, Baudoin FM, Luckman SM. Endocrinology. 2002 Jan;143(1):155-62.

[3] Effect of growth hormone (GH)-releasing hormone (GHRH), atropine, pyridostigmine, or hypoglycemia on GHRP-6-induced GH secretion in man. Peñalva A, Carballo A, Pombo M, Casanueva FF, Dieguez C. J Clin Endocrinol Metab. 1993 Jan;76(1):168-71.

[4] Growth hormone-releasing peptides and their 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 Functional Growth Hormone-Releasing Peptide Receptors. Ilan Shimon, Xinmin Yan, and 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 new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Bowers CY, Momany FA, Reynolds GA, Hong A. 1984 Endocrinology. 114:1537–1545.

[9] Effect of a new synthetic hexapeptide to selectively stimulate growth hormone release in healthy human subjects. Ilson BE, Jorkasky DK, Curnow RT, Stote RM. 1989 J Clin Endocrinol Metab. 69:212–214.

[10] On the actions of the growth hormone-releasing hexapeptide, GHRP. Bowers CY, Sartor AO, Reynolds GA, Badger TM. 1991 Endocrinology. 128:2027–2035.

[11] Blocked growth hormone-releasing peptide (GHRP-6)-induced GH secretion and absence of the synergic action of GHRP-6 plus GH-releasing hormone in patients with hypothalamopituitary disconnection: evidence that GHRP-6 main action is exerted at the hypothalamic level. V Popovic, S Damjanovic, D Micic, M Djurovic, C Dieguez, and F 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. Dickson SL, Leng G, Robinson ICAF. 1993 Neurosci Lett. 53:303–306.

[13] Pharmacokinetic study of Growth Hormone-Releasing Peptide 6 (GHRP-6) in nine male healthy 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. Eur J Pharm Sci. 2013 Jan 23;48(1-2):40-6. doi: 10.1016/j.ejps.2012.10.006. Epub 2012 Oct 23.