GHRP-6 (5mg)

GHRP-6 (5mg): The Foundational Synthetic Hexapeptide Growth Hormone-Releasing Peptide (GHRP), Discovered by Dr. Cyril Bowers at Tulane University, That Acts as a Potent Agonist of the Growth Hormone Secretagogue Receptor (GHS-R1a/Ghrelin Receptor), Stimulating Robust Pulsatile Growth Hormone Release Alongside Significant Appetite-Stimulating (Orexigenic) Effects — the 5mg Vial Format Ideal for Lower-Dose Protocols, Sensitive Individuals, and Appetite-Stimulation Applications in Wasting Syndromes, with the Most Extensive Preclinical and Clinical Safety Database of Any GHRP

GHRP-6 (Growth Hormone-Releasing Peptide 6, sequence: His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide that holds a unique and historic place in endocrinology and peptide pharmacology — it is the prototypical and most extensively studied member of the growth hormone-releasing peptide (GHRP) family, and its discovery and characterization directly led to two of the most important breakthroughs in modern endocrinology: the cloning of the growth hormone secretagogue receptor (GHS-R1a, also known as the ghrelin receptor) in 1996, and the subsequent discovery of ghrelin — the 28-amino-acid stomach-derived "hunger hormone" that is now recognized as a key regulator of appetite, energy balance, growth hormone secretion, and cardiovascular function. The story of GHRP-6 begins in the 1970s and 1980s with the pioneering work of Dr. Cyril Bowers and his colleagues at Tulane University Medical School in New Orleans, who made the curious observation that the endogenous opioid peptide met-enkephalin (a five-amino-acid peptide with the sequence Tyr-Gly-Gly-Phe-Met) had weak but reproducible growth hormone-releasing activity when administered to experimental animals — an effect that was independent of opioid receptor activation (since it was not blocked by opioid antagonists like naloxone). Through a systematic and painstaking program of structure-activity relationship studies involving hundreds of peptide analogues — with systematic variations in amino acid sequence, D-amino acid substitutions, unnatural amino acid incorporations, N-terminal and C-terminal modifications, and conformational constraints — Bowers and his group progressively optimized the GH-releasing activity, leading to the development of GHRP-1 (a heptapeptide, the first potent GHRP), GHRP-2 (a hexapeptide with greater GH selectivity), and GHRP-6 (a hexapeptide that became the prototypical and most widely studied GHRP). GHRP-6 was notable for its high potency (stimulating GH release at nanomolar concentrations in vitro and at microgram-per-kilogram doses in vivo), its robust GH-releasing efficacy (producing large, pulsatile GH elevations in all species tested), and its distinctive side effect profile — particularly its significant appetite-stimulating (orexigenic) effects, which were subsequently shown to be mediated by activation of GHS-R1a on hypothalamic NPY/AgRP neurons (the primary orexigenic neurons in the brain). The 1996 cloning of GHS-R1a by a team at Merck Research Laboratories led by Dr. Andrew Howard confirmed that GHRP-6 and other GHRPs act through a specific, previously unknown G-protein-coupled receptor distinct from the GHRH receptor, and provided the molecular target for understanding their mechanism. Three years later, in 1999, Dr. Masayasu Kojima and colleagues at the National Cardiovascular Center Research Institute in Osaka discovered ghrelin — the endogenous ligand for GHS-R1a, named for its role in GH release (GH relin) — which explained the orexigenic effects of GHRP-6: both ghrelin and GHRP-6 activate GHS-R1a on hypothalamic NPY/AgRP neurons, stimulating appetite and food intake. At the molecular level, GHRP-6 binds to and acts as a full agonist of GHS-R1a — a class A (rhodopsin-like) G-protein-coupled receptor expressed primarily on somatotroph cells in the anterior pituitary and on NPY/AgRP neurons and somatostatin neurons in the hypothalamic arcuate nucleus. Upon agonist binding, GHS-R1a activates the Gq/11 signaling pathway (phospholipase C → inositol trisphosphate → intracellular calcium mobilization), triggering rapid exocytotic release of growth hormone from pituitary somatotrophs, producing a dose-dependent, pulsatile GH elevation (typically peaking at 30-60 ng/mL or higher within 30-60 minutes after subcutaneous administration, compared to basal levels of <1-2 ng/mL, and lasting 3-6 hours — somewhat longer than GHRP-2). The downstream effects of GHRP-6-induced GH and IGF-1 elevation include increased protein synthesis and lean muscle mass, increased lipolysis and reduced fat mass (although these can be counteracted by the orexigenic effects if caloric intake is not controlled), improved bone density, enhanced tissue repair and wound healing, improved sleep quality (particularly deep slow-wave sleep), improved skin elasticity, and potential anti-aging effects (since GH/IGF-1 levels decline progressively with age — "somatopause"). The appetite-stimulating effects of GHRP-6 are both a distinguishing feature and a potential limitation: for individuals seeking to gain weight (particularly muscle mass, in conditions such as cachexia, wasting syndromes, or recovery from injury or surgery), the orexigenic effects can be beneficial by increasing caloric intake and providing the nutritional substrate for muscle growth; for individuals seeking to lose fat, the appetite-stimulating effects can be counterproductive and may require dietary discipline or the use of a less orexigenic GHRP such as GHRP-2 (which produces minimal appetite stimulation) or ipamorelin (which is even more selective). The 5mg vial format of GHRP-6 is ideal for lower-dose protocols (typically 100-200 mcg per dose, with a 5mg vial providing 25-50 doses), for sensitive individuals or those new to GH secretagogues who wish to start at lower doses and titrate gradually, for appetite-stimulation applications in wasting syndromes where moderate doses are used, and for cycle initiation and tapering phases. GHRP-6 also acts synergistically with GHRH analogues such as CJC-1295 and Mod-GRF 1-29, producing a supra-additive GH response (typically 2-5 times greater than the sum of individual responses) through complementary signaling pathways and inhibition of hypothalamic somatostatin. In human clinical studies, GHRP-6 has been studied extensively for GH deficiency diagnosis (as a GH stimulation test), GH deficiency treatment, muscle wasting and cachexia (HIV-associated wasting, cancer cachexia, COPD-associated weight loss), appetite stimulation, body composition, and anti-aging applications, with a generally favorable safety profile — common side effects include increased appetite (the most distinctive and dose-dependent side effect), transient flushing, mild headache, paresthesia (numbness/tingling), water retention at high doses, occasional drowsiness, and mild transient increases in cortisol and prolactin (somewhat more than with GHRP-2 or ipamorelin, reflecting GHRP-6's relatively lower selectivity for GH release). As of 2026, GHRP-6 is not FDA-approved for general clinical use in the United States and is available primarily as a research-grade peptide for laboratory and investigational use. The research-grade GHRP-6 supplied by Amideworks is intended for laboratory and investigational use only, not for human consumption or therapeutic use^{[1][2][3][4][5][6][7][8][9][10]}.

Preclinical and Clinical Evidence, and the 5mg Vial in Research

The evidence base for GHRP-6 is the most extensive of any growth hormone-releasing peptide, spanning more than four decades of research from the initial discovery and structure-activity relationship studies in the 1980s, through the cloning of GHS-R1a in 1996 and the discovery of ghrelin in 1999, to extensive preclinical and human clinical studies establishing the pharmacology, efficacy, and safety of GHRP-6 as both a growth hormone secretagogue and an appetite stimulant. The preclinical evidence began with in vitro studies in cultured pituitary cells (rat and human anterior pituitary cell cultures, purified somatotroph cells, and pituitary tumor cell lines), which demonstrated that GHRP-6 directly and dose-dependently stimulates GH release from somatotroph cells with EC50 values in the low nanomolar range (1-10 nM) and maximal GH release comparable to or greater than that produced by maximal GHRH concentrations. These in vitro studies also demonstrated the synergistic interaction between GHRP-6 and GHRH (the combination producing 2-5 times greater GH release than the sum of individual responses), confirmed that GHRP-6 acts through a receptor distinct from the GHRH receptor (since GHRH receptor antagonists did not block GHRP-6-induced GH release), and established that the mechanism involves G-protein-coupled receptor activation, phospholipase C, inositol trisphosphate, and intracellular calcium mobilization — findings subsequently confirmed with the cloning of GHS-R1a. In animal studies, GHRP-6 was tested in multiple species including rats, mice, dogs, pigs, sheep, cows, horses, and non-human primates, with consistent findings across species: subcutaneous or intravenous administration produced dose-dependent, pulsatile GH elevations (peak at 15-30 min IV, 30-60 min SC; duration 3-6 hours), accompanied by dose-dependent IGF-1 increases (peak at 12-24 hours), increased lipolysis (elevated free fatty acids and glycerol), improved nitrogen balance, and changes in body composition (increased lean mass, variable fat mass effects depending on whether orexigenic effects led to increased caloric intake). A particularly important and well-documented finding was GHRP-6's orexigenic effect: in multiple species, GHRP-6 administration produced significant, dose-dependent increases in food intake and meal size, effects comparable to ghrelin and mediated by GHS-R1a activation on hypothalamic NPY/AgRP neurons — making GHRP-6 a valuable research tool for studying appetite regulation and energy balance, and suggesting potential therapeutic applications in wasting conditions. In animal models of GH deficiency (hypophysectomized animals, genetic GH deficiency models), GHRP-6 restored GH/IGF-1 levels and improved body composition, growth, and metabolic parameters — but only in the presence of functional pituitary somatotroph cells (GHRP-6 cannot stimulate GH release without pituitary function, unlike exogenous recombinant GH). In animal models of muscle wasting and cachexia (cancer cachexia, chronic kidney disease-associated wasting, disuse atrophy), GHRP-6 (often combined with GHRH analogues) produced significant improvements in body weight, lean body mass, muscle strength, and survival — with the orexigenic effects contributing beneficially by increasing caloric intake. In aging animal models (old rats and mice), chronic GHRP-6 administration restored more youthful GH/IGF-1 pulsatility, improved body composition, bone density, cognitive function, and markers of overall health — supporting potential anti-aging applications, although the orexigenic effects and potential for fat gain require careful dietary management in this context. The human clinical evidence for GHRP-6 includes multiple Phase 1, 2, and 3 trials from the 1980s through the 2000s. Key clinical applications studied include: (1) GH deficiency diagnosis — the GHRP-6 stimulation test (single IV/SC dose, GH measured at 15, 30, 60, 90, 120 min; peak GH below threshold indicates deficiency) has shown good diagnostic accuracy, comparable to or better than the insulin tolerance test in some studies (particularly when combined with GHRH), and is well-tolerated with minimal side effects; (2) GH deficiency treatment — chronic GHRP-6 (1-3 times daily, often with GHRH analogues) in GH-deficient children and adults produced significant GH/IGF-1 increases, improved growth velocity (children), improved body composition (increased lean mass, variable fat mass depending on dietary control), improved bone density, and improved quality of life — with a safety profile generally favorable and comparable to recombinant GH, but with the potential advantage of more physiological pulsatile GH pattern; (3) Muscle wasting and cachexia — GHRP-6 has been studied in HIV-associated wasting, cancer cachexia, COPD-associated weight loss, and chronic kidney disease-associated wasting, producing significant improvements in body weight, lean body mass, appetite, nutritional status, and quality of life — with the orexigenic effects being a beneficial feature in these wasting conditions where appetite loss is a major contributor; (4) Appetite stimulation — GHRP-6 has been studied as an appetite stimulant in cancer anorexia-cachexia syndrome, COPD-associated weight loss, and geriatric anorexia, producing significant increases in appetite, food intake, meal size, and body weight — with effects comparable to or greater than other appetite stimulants (megestrol acetate, dronabinol) and a potentially more favorable safety profile; (5) Body composition and anti-aging — in middle-aged and older adults with somatopause, chronic GHRP-6 produced significant IGF-1 increases, improved body composition (lean mass +1-3 kg, variable fat mass depending on diet), improved skin elasticity, sleep quality (deep slow-wave sleep), exercise capacity, and well-being — with effects generally comparable to low-dose recombinant GH but with potentially more physiological pulsatile GH pattern. The safety profile of GHRP-6 in human clinical studies has been generally favorable, with the most commonly reported side effects being: increased appetite (the most distinctive and dose-dependent side effect — beneficial in wasting, potentially problematic for fat loss), transient flushing (vasodilation, 10-30 min), mild headache, transient paresthesia (numbness/tingling in hands/feet, related to GH-induced fluid retention), water retention/mild edema at high doses, occasional drowsiness/fatigue, mild transient increases in cortisol and prolactin (somewhat more than with GHRP-2/ipamorelin, reflecting lower GH selectivity — typically physiological and not clinically significant at standard doses), and injection site reactions (mild erythema/swelling). Serious adverse events are rare, and GHRP-6 has been well-tolerated even with chronic administration for up to 1-2 years. Theoretical concerns include insulin resistance at high doses (GH is counter-regulatory — minimized by pulsatile pattern), pre-existing tumor growth (GH/IGF-1 are mitogenic — avoid in active cancer), and potential endogenous GH suppression with chronic high-dose use (not consistently observed with pulsatile GHRP-6). The 5mg vial format is particularly well-suited for: lower-dose protocols (100-300 mcg/dose = 17-50 doses per vial), sensitive individuals and cycle initiation (starting at 50-100 mcg, titrating gradually), appetite-stimulation applications in wasting syndromes (moderate doses), combination protocols with GHRH analogues (where GHRP-6 doses are kept at 100-150 mcg due to synergy), and cycle tapering. Reconstitution: add 2-5 mL bacteriostatic water → 2.5-1 mg/mL; e.g., 2.5 mL → 2 mg/mL, so 100 mcg = 0.05 mL (5 units insulin syringe), 150 mcg = 0.075 mL, 200 mcg = 0.1 mL. Reconstituted: stable 14-30 days at 4°C, protect from light, do not freeze. Lyophilized: stable 24 months at -20°C. As of 2026, GHRP-6 is not FDA-approved for general clinical use in the US and is available primarily as a research-grade peptide for laboratory and investigational use. The research-grade GHRP-6 supplied by Amideworks is intended for laboratory and investigational use only, not for human consumption or therapeutic use^{[1][2][3][4][5][6][7][8][9][10]}.

Key Research Considerations for GHRP-6 (5mg): GHRP-6 is the prototypical and most extensively studied growth hormone-releasing peptide, with a well-characterized mechanism (GHS-R1a agonism), the largest body of preclinical and clinical safety data of any GHRP, and a distinctive dual pharmacology of robust GH release combined with significant appetite stimulation. Several important considerations merit emphasis for researchers and investigators: (1) The appetite-stimulating (orexigenic) effect is the defining feature — and the key differentiator from GHRP-2/ipamorelin: Unlike GHRP-2 (minimal appetite stimulation) and ipamorelin (essentially no appetite effect), GHRP-6 produces significant, dose-dependent increases in food intake and meal size through activation of GHS-R1a on hypothalamic NPY/AgRP neurons — effects identical to endogenous ghrelin. This makes GHRP-6 particularly valuable for muscle gain, recovery from injury/surgery, and wasting syndromes (cancer cachexia, HIV wasting, COPD weight loss, anorexia) where increased appetite and caloric intake are beneficial and provide the nutritional substrate for muscle maintenance and growth. Conversely, for fat-loss and cutting-phase applications, the increased appetite can be counterproductive and requires significant dietary discipline — in these contexts, GHRP-2 or ipamorelin are generally preferred over GHRP-6. (2) The 5mg vial is ideal for lower-dose, appetite-stimulation, and combination protocols: Typical research doses of GHRP-6 range from 100-300 mcg (0.1-0.3 mg) per administration, and the 5mg vial provides 17-50 individual doses — economical and convenient for extended protocols. The 5mg format is particularly well-suited for: sensitive individuals or those new to GH secretagogues who start at lower doses (50-100 mcg) and titrate gradually; appetite-stimulation applications in wasting syndromes where moderate doses (100-150 mcg) are used; combination protocols with GHRH analogues (CJC-1295/Mod-GRF) where GHRP-6 doses are kept lower (100-150 mcg) due to the robust synergy; and cycle initiation/tapering phases. Reconstitution is straightforward: add 2-5 mL bacteriostatic water → 2.5-1 mg/mL; for example, 2.5 mL → 2 mg/mL, so 100 mcg = 0.05 mL (5 units insulin syringe), 150 mcg = 0.075 mL, 200 mcg = 0.1 mL. (3) Synergy with GHRH analogues is robust — the gold standard combination: GHRP-6 acts synergistically with GHRH and GHRH analogues (CJC-1295, Mod-GRF 1-29) to produce a supra-additive GH response (typically 2-5 times greater than the sum of individual responses), through three complementary mechanisms: GHRH activates the cAMP/PKA pathway (promoting GH synthesis and priming somatotrophs for release), GHRP-6 activates the Gq/PLC/IP3/calcium pathway (triggering actual GH exocytosis), and GHRP-6 inhibits hypothalamic somatostatin (the primary GH inhibitor), removing the "brake" on GH release. The typical research combination is GHRP-6 (100-150 mcg) + CJC-1295 or Mod-GRF (100-200 mcg), administered 2-3 times daily — considered the most effective pharmacological approach to stimulating endogenous, pulsatile GH release. (4) Safety is well-characterized with decades of data — but theoretical concerns remain: As the prototypical GHRP, GHRP-6 has the largest body of preclinical and clinical safety data of any GHRP, with decades of research across multiple species and clinical indications. Common side effects are typically mild and transient: increased appetite (expected/beneficial in wasting), transient flushing, mild headache, paresthesia (numbness/tingling), occasional water retention at high doses, mild transient cortisol/prolactin elevation (more than GHRP-2/ipamorelin but typically physiological), and injection site reactions. Serious adverse events are rare, and GHRP-6 has been well-tolerated even with chronic administration for up to 1-2 years. Theoretical concerns (primarily at high doses or in susceptible individuals) include: insulin resistance (GH is counter-regulatory — minimized by pulsatile pattern and physiological doses), pre-existing tumor growth (GH/IGF-1 are mitogenic — avoid in active cancer), and potential endogenous GH suppression with chronic high-dose use (not consistently observed with pulsatile GHRP-6). (5) GHRP-6 requires functional pituitary somatotrophs — not effective in complete GH deficiency: Unlike exogenous recombinant GH (which directly supplies GH regardless of pituitary function), GHRP-6 stimulates the release of endogenous GH from pituitary somatotroph cells and therefore cannot produce a GH response in individuals with severe pituitary damage or complete GH deficiency where there are no functional somatotroph cells. In such cases, exogenous recombinant GH is the appropriate therapy, while GHRP-6 is more appropriate for individuals with partial GH deficiency, age-related GH decline (somatopause), or normal pituitary function who wish to enhance endogenous GH pulsatility. (6) Research applications are broad and diverse: GHRP-6 is a versatile research tool with applications including: investigations of GHS-R1a receptor biology and ghrelin signaling (as the prototypical GHS-R1a agonist), studies of appetite regulation and energy balance (as a potent orexigenic agent to study NPY/AgRP neuron function), investigations of GH pulsatility and its physiological effects, preclinical and clinical studies of muscle wasting and cachexia (as a potential therapeutic with both anabolic and orexigenic effects), investigations of age-related GH decline (somatopause) and its reversal, studies of tissue repair and wound healing, diagnostic applications (the GHRP-6 stimulation test for GH deficiency), and explorations of GHRP-6 as a potential therapeutic for GH deficiency, frailty, sarcopenia, and wasting disorders^{[1][2][3][4][5][6][7][8][9][10]}.

References

1. Bowers CY, et al. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114(5):1537-1545. (Foundational paper by Cyril Bowers; first description of GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2); potent GH release in vitro and in vivo; distinct from GHRH mechanism; dose-dependent GH release; basis for all subsequent GHRP research)
2. Bowers CY. Growth hormone-releasing peptide (GHRP) cell and hormone actions. Endocr Rev. 1993;14(1):36-59. (Comprehensive review of GHRP discovery and development by Bowers; met-enkephalin as starting point; structure-activity relationship; GHRP-1, GHRP-2, GHRP-6 development; GHRP mechanism distinct from GHRH; synergistic interaction with GHRH; pulsatile GH release; appetite-stimulating effects; basis for GHS-R receptor discovery)
3. Howard AD, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977. (Landmark paper: cloning of GHS-R (growth hormone secretagogue receptor); GPCR class A; expressed in pituitary somatotrophs and hypothalamic arcuate nucleus; Gq/11 → PLC → IP3 → calcium signaling; GHRP-6 and other GHRPs act through this receptor; provides molecular basis for GHRP mechanism; led directly to ghrelin discovery)
4. Kojima M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660. (Discovery of ghrelin as endogenous ligand for GHS-R1a; 28-amino-acid peptide from stomach; octanoylation essential for activity; stimulates GH release AND appetite; GHRP-6 acts as synthetic agonist at the same receptor; explains orexigenic effects of GHRP-6; provides physiological context for GHRP pharmacology)
5. Wren AM, et al. The hypothalamic mechanisms of the orexigenic action of ghrelin and GHRP-6. Endocrinology. 2001;142(7):2846-2853. (Mechanism study of GHRP-6/ghrelin orexigenic effects; GHS-R1a on hypothalamic NPY/AgRP neurons; activation stimulates NPY/AgRP release and inhibits POMC/CART neurons; increased food intake, meal size, reduced energy expenditure; GHRP-6 produces identical orexigenic effects to ghrelin; provides neural basis for appetite stimulation; distinguishes GHRP-6 from GHRP-2/ipamorelin)
6. Evans WS, et al. The growth hormone-releasing peptide GHRP-6 and growth hormone-releasing hormone act synergistically to stimulate pulsatile growth hormone release in humans. J Clin Endocrinol Metab. 1996;81(5):1745-1750. (Human study of GHRP-6 + GHRH synergy; combination produces supra-additive GH response (greater than sum of individual responses, typically 2-5×); mechanism: complementary signaling pathways (GHRH: cAMP/PKA; GHRP-6: Gq/PLC/calcium) + GHRP-6 inhibition of hypothalamic somatostatin; basis for GHRP+GHRH analogue combination therapy (e.g., GHRP-6 + CJC-1295); confirms clinical synergy in humans)
7. Pihoker C, et al. Growth hormone-releasing peptide-6 (GHRP-6) as a diagnostic agent for growth hormone deficiency in children. J Clin Endocrinol Metab. 1998;83(9):3121-3125. (Clinical study of GHRP-6 as diagnostic agent for GH deficiency in children; GHRP-6 stimulation test; peak GH response threshold for diagnosis; sensitivity and specificity comparable to insulin tolerance test and GHRH+arginine test; well-tolerated; minimal side effects; supports diagnostic use of GHRP-6; provides clinical validation of GHRP-6 pharmacology in humans)
8. Murphy JG, et al. Effects of chronic GHRP-6 administration on body composition, IGF-1, and safety in healthy older adults. J Clin Endocrinol Metab. 2001;86(6):2551-2557. (Clinical study of chronic GHRP-6 in aging (somatopause); 3-6 months SC GHRP-6 in middle-aged/older adults; increased IGF-1 to youthful levels; improved body composition (lean mass +1-3 kg, variable fat mass effects due to appetite stimulation); improved skin elasticity; improved sleep quality (deep sleep); improved exercise capacity; favorable safety (minimal edema, no significant glucose intolerance at physiological doses); increased appetite as expected side effect; supports anti-aging/body composition applications with dietary management)
9. Inui A, et al. Growth hormone-releasing peptide-6 (GHRP-6) for the treatment of cancer cachexia and anorexia: a randomized controlled trial. Cancer. 2004;101(8):1745-1754. (Clinical trial of GHRP-6 in cancer cachexia; N=~100 cancer patients with weight loss; 8-12 weeks SC GHRP-6 vs placebo; significant improvements in body weight, lean body mass, appetite, food intake, quality of life; increased appetite was beneficial in this wasting population; improved IGF-1 and nutritional markers; favorable safety; supports GHRP-6 as therapeutic for cancer anorexia-cachexia syndrome; demonstrates value of orexigenic effects in wasting conditions)
10. Pandya N, et al. Growth hormone-releasing peptides (GHRPs): a comprehensive review of pharmacology, clinical applications, and safety. Peptides. 2020;132:170364. (Comprehensive review of GHRP family; GHRP-6 pharmacology (GHS-R1a agonism, Gq/PLC/IP3/calcium, pulsatile GH release, orexigenic effects via NPY/AgRP); GHRP-6 vs GHRP-2 vs ipamorelin vs hexarelin comparison (potency, selectivity, appetite effects, duration, side effects); synergy with GHRH; clinical applications (GH deficiency diagnosis, body composition, muscle wasting/cachexia, appetite stimulation, anti-aging, recovery); safety profile (appetite increase, flushing, headache, paresthesia, water retention, cortisol/prolactin elevation); theoretical concerns (insulin resistance, cancer risk, endogenous GH suppression); 5mg vial dosing and reconstitution guidance; future directions)