Follistatin 344 vs Hexarelin

Binds and neutralizes myostatin (GDF-8) and activin; removes the natural brake on muscle growth allowing supraphysiological hypertrophy

Follistatin-344 is the predominant endogenous isoform of follistatin, a glycoprotein that binds and neutralizes the TGF-β superfamily members activin A and myostatin, preventing their engagement with skeletal muscle ActRII receptors and thereby relieving their inhibitory effects on muscle protein synthesis and satellite cell activation. By sequestering both myostatin and activin A simultaneously, follistatin-344 neutralizes two complementary negative regulators of muscle growth through a dual-pathway mechanism, a property that distinguishes it from agents that target only the myostatin pathway. Transgenic expression of human follistatin-344 has produced significant skeletal muscle mass increases in animal models, and a phase 1/2a gene therapy trial delivering the follistatin-344 gene via AAV to patients with Becker muscular dystrophy established initial proof of concept and safety data in a human clinical context. Follistatin-344 has not received FDA approval for any indication; exogenous administration as a recombinant protein or peptide is investigational and no human safety data exists for this route of administration outside gene therapy trial contexts. Follistatin-344 as a research compound: recombinant follistatin-344 protein is available through research biochemical suppliers as a laboratory reagent, used in cell culture and animal models to probe myostatin and activin A biology. Interest in exogenous follistatin-344 administration in performance contexts has grown from the animal model hypertrophy data; however, the protein's large molecular weight (~35 kDa glycoprotein) creates significant bioavailability challenges for subcutaneous or intramuscular routes, and no human pharmacokinetic data supports assumed tissue distribution from injection. This distinguishes it from smaller peptide-based myostatin modulators. Follistatin-344 vs myostatin propeptide: both target myostatin inhibition but through different binding mechanisms. Follistatin-344 binds activin A in addition to myostatin, providing a broader TGF-β inhibition profile. Myostatin propeptide is the endogenous inhibitory domain of the myostatin precursor protein — it is myostatin-specific but structurally derived from the same protein rather than from a binding antagonist class. Both compounds remain at the research stage for performance applications with no approved human use. Providers offering research peptides in the performance and muscle recovery category are listed in the PeptideBase directory.

Potent synthetic GHRP; strongest GH secretagogue in its class; also activates CD36 scavenger receptor for cardioprotective effects

Hexarelin is a synthetic hexapeptide GH secretagogue that acts as an agonist at the ghrelin receptor (GHS-R1a) and is among the most potent GHRP-class peptides characterized in human studies, producing robust GH release at low doses via a mechanism that synergizes with endogenous GHRH and partially suppresses somatostatin. In addition to its pituitary GHS-R1a effects, hexarelin has been shown to engage CD36 receptor-mediated pathways in cardiac tissue, suggesting biological activity beyond GH secretion, though the cardiac pharmacology has not been developed into an approved clinical application. Human endocrine studies have directly compared hexarelin-induced GH release with ghrelin and GHRH in healthy volunteers, confirming its potent pituitary activity; repeated administration produces progressive attenuation of the GH response consistent with receptor desensitization. Hexarelin is not FDA-approved for any indication; it is used as a research tool for characterizing the GH secretagogue receptor system and has not been evaluated for safety or efficacy in performance enhancement contexts. Research interest in hexarelin centers on two distinct biological roles: its potent GH-secreting activity — relevant to muscle recovery and body composition research contexts — and its cardiac tissue effects via CD36 receptor pathways, which distinguish it mechanistically from simpler GHRPs such as GHRP-2 and GHRP-6. Hexarelin dosage in research contexts: published human studies have used intravenous doses of 1–2 mcg/kg to characterize GH secretion kinetics. In clinical research protocols, subcutaneous doses of 100–200 mcg per injection are most commonly cited, typically administered once or twice daily. Hexarelin's potency relative to other GHRPs means lower doses are required for equivalent GH stimulation; however, receptor desensitization with repeated dosing is more pronounced than with selective peptides such as ipamorelin, which has driven research interest in cycling protocols and combination approaches. Administration is by subcutaneous injection. Hexarelin vs ipamorelin: the two peptides differ substantially in selectivity and desensitization profile. Hexarelin is a non-selective GHRP that stimulates GH alongside modest elevations in cortisol, prolactin, and ACTH — effects documented in human challenge studies. Ipamorelin, by contrast, is one of the most selective GHRPs characterized, producing GH secretion with minimal cortisol or prolactin co-stimulation. For research focused specifically on GH secretion with a cleaner hormonal background, ipamorelin is generally preferred; hexarelin is studied in contexts where its dual CD36/GHS-R1a pharmacology is the research focus. Providers offering hexarelin are listed in the PeptideBase directory.