You pose a good question. Here's the gist:
MK-677 does affect the
hGH-IGF-I axis, but not exclusively. Whereas
GHRP6 is a potent synthetic ghrelin mimetic
(6), all it does is affect
GH and the downstream effects it causes.
MK-677 affects a wide array of tissues, including but not limited to recomposition of total body fat, restoration of
LDL cholesterol parameters
(1)(2), Acceleration of bone matrix synthesis parameters
(3), helps restore vitality to the heart and cardiovascular system
(4), Prevent damage and age related death to heart muscle cells
(5) and
much more. Here's a link to a comprehensive article on this forum I recommend you read:
https://www.isarms.com/forums/stero...mk-677-power-compound-compels-you!-13054.html
Assuming you don't care about all of those benefits that
MK-677 would hold over
GHRP-6, I'll answer your core question: Which one is more effective with respect to affecting the
GH axis?
Simple.
MK-677 results in long, sustainable effects on the
GH-IGF-I axis. It causes the set point of the CNS neuro-secretory system to rise over time and changes the baseline. It takes longer to kick into effect, and lasts longer, causing a more
sustainable effect on this axis.
GHRP-2 is more potent but quick to act, quick to dissipate, and leaves virtually no long lasting effects in a similar fashion
(6). Once you stop administration, the benefits stop, notwithstanding it not having any of the additional benefits mentioned with respect to
MK-677.
Think of
MK-677 as the marathon runner, in it to produce long standing results that are sustainable;
GHRP-2 would be a better choice if you wanna dash 100 yards really quickly by comparison. Both are effective in their own way.
GHRP-2 is quite effective at what it does, even though I hadn't done much research into it yet (maybe if there's demand), but in order to enjoy its short lasting specific effects, it would have to be administered regularly, daily and indefinitely.
References
(1)Nass, R., Pezzoli, S.S., Oliveri, M.C. et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: A randomized trial/ Ann Intern Med. 2008; 149: 601–611
(2)Katz, A., Nambi, S.S., Mather, K. et al. Quantitative insulin sensitivity check index: A simple, accurate method for assessing insulin sensitivity in human. J Clin Endocrinol Metab. 2000; 85: 2402–2410
(3)MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study/ Adunsky A, Chandler J, Heyden N, Lutkiewicz J, Scott BB, Berd Y, Liu N, Papanicolaou DA; Archives of Gerontology and Geriatrics (2011);
(4)The effects of growth hormone and insulin-like growth factor-1 on the aging cardiovascular system and its progenitor cells/ Devin JK, Young PP; Current Opinion in Investigational Drugs, London (2008)
(5)Ghrelin and des-acyl ghrelin inhibit cell death in cardiomyocytes and endothelial cells through ERK1/2 and PI 3-kinase/AKT/ Gianluca B, Nicoletta F, Santina C, Filomena C et al.; The Journal of Cell Biology(2002)
(6)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). "Pharmacokinetic study of Growth Hormone-Releasing Peptide 6 (GHRP-6) in nine male healthy volunteers". Eur J Pharm Sci. 48 (1-2): 40–6.
