Follistatin 344

Mechanism of action: Binds and inhibits myostatin; Binds and inhibits activin; Removes natural brakes on skeletal muscle growth (preclinical/animal data)

Proposed indications: Myostatin inhibition (preclinical); Muscle growth (animal data); Muscle preservation (research)

Commonly reported by peptide clinics†: 100-300 mcg/day, 1-2 week cycles

Research-chemical community sources commonly report 100-300 mcg/day for short cycles, typically 1-2 weeks, reflecting its cost and a commonly reported (anecdotal) side effect of joint discomfort. No human clinical trials exist for this use -- this reflects community convention, not evidence.

†Reported by peptide clinics and compounding pharmacies -- not derived from human clinical trials. Not an individualized recommendation. Actual use should be supervised by a qualified provider.

Typical clinical dosing schedule: No established clinical dosing. Not an approved therapeutic agent; used in laboratory/research settings only.

Administration: Subcutaneous injection (research settings) — No established clinical dosing

Compare with: ACE-031 (Fusion Protein — Not a True Peptide)IGF-1 LR3 (Long R3 IGF-1)PEG-MGF (Pegylated Mechano Growth Factor)

An "emerging / limited evidence" rating means rigorous research hasn't caught up yet -- not that this peptide doesn't work. Many peptides in this category are newer or simply understudied rather than proven ineffective.

Evidence rating: ⭐⭐⭐☆☆ — Preclinical and animal research demonstrates myostatin inhibition and muscle growth effects; robust human clinical trial data are lacking, and myostatin-pathway inhibition has raised safety questions in other investigational compounds (see ACE-031).

Common side effects: Human safety profile remains incompletely characterized.

Serious risks: Unknown long-term safety; Myostatin/activin pathway inhibition (the same pathway targeted by ACE-031, a different, unrelated compound) has been associated with vascular adverse effects in that specific investigational program — this is noted as pathway-level context, not evidence that follistatin itself causes those effects; long-term effects of sustained myostatin/activin inhibition in humans generally are not well characterized.

Legal status: Not FDA-approved for human use. This is a research compound, not a medication — any use should only occur under the direction of a licensed healthcare provider, and its legal availability varies and changes frequently. Verify current status independently before considering use.

Regulatory status: Research peptide • Not FDA approved

Contraindications: Not established. Avoid in:; Pregnancy; Active malignancy; Uncontrolled illness outside research settings

Pregnancy & breastfeeding: Avoid.

Rodino-Klapac LR, Haidet AM, Kota J, et al. (2009). Inhibition of myostatin with emphasis on follistatin as a therapy for muscle disease. Muscle & Nerve. Chang F, Fang R, Wang M, et al. (2017). The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs. Transgenic Research.