IGF-1 LR3 + Follistatin-344 Blend
How this combination works
The community rationale pairs an IGF-1 analogue that stimulates muscle growth through the IGF-1 receptor with follistatin, which removes myostatin's brake on muscle growth. Both pathways converge on Akt signalling. Neither compound has any human efficacy data for muscle or strength — every muscle finding for both is from animal models — and no study has tested them together. Follistatin-344 has been associated with central serous chorioretinopathy in all 11 reported human cases after high-dose injection. This rationale is mechanistic inference only.
Combined mechanism
IGF-1 LR3 is a synthetic IGF-1 analogue with an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. It has markedly reduced affinity for IGF-binding proteins while keeping high IGF-1 receptor affinity, which gives more free ligand and prolonged receptor signalling. Receptor binding activates ERK and PI3K. Follistatin-344 is an activin-binding glycoprotein. Because myostatin is related to activin, follistatin also inhibits myostatin signalling. Overexpression in skeletal muscle suppresses Smad2 phosphorylation and activates Akt, producing myofibre hypertrophy. Its heparin-binding domain causes rapid tissue sequestration and a short systemic half-life. Both converge on Akt-mediated growth signalling. No human pharmacokinetic, pharmacodynamic or safety data exist for either compound's muscle effects or for the combination.
What each component does
Evidence base for this combination
Safety considerations for this combination
- No combination-specific safety data exist for IGF-1 LR3 + Follistatin-344. The signals below come from each compound studied on its own. Component approved files
- Both compounds promote growth signalling (IGF-1R/PI3K and Akt). IGF-1 LR3 accelerated tumour growth in two animal cancer models. Adding a second growth-promoting agent is an unstudied compounding of that concern. IGF-1 LR3: PMID: 31285507, 8053901. Follistatin-344: PMID: 27787698
- Attenuation of glucose-stimulated insulin secretion (intrinsic islet defect) following 1-week infusion in fetal sheep; lower plasma insulin and glucose concentrations observed. Inherited from IGF-1 LR3 (PMID: 33938236)
- Reduced fetal circulating amino acid concentrations following 1-week LR3 IGF-1 infusion in growth-restricted fetal sheep, potentially reflecting altered substrate availability. Inherited from IGF-1 LR3 (PMID: 39679943)
- Accelerated tumour growth in C26 tumour-bearing mice treated with LR3 IGF-I, despite limiting loss of muscle mass. Inherited from IGF-1 LR3 (PMID: 31285507)
- Decreased food intake, reduced circulating insulin and glucose, and increased tumour growth in mammary adenocarcinoma-bearing rats infused with LR3-IGF-I. Inherited from IGF-1 LR3 (PMID: 8053901)
- Central serous chorioretinopathy (CSCR): 11 male bodybuilding athletes developed CSCR after high-dose subcutaneous FS344 injections; 10 had unilateral and 1 had bilateral findings. In 8 patients with a single injection, subretinal fluid resolved within a mean of 2.3 ± 0.7 months. Recurrent CSCR developed in 3 patients with multiple injection histories. Inherited from Follistatin-344 (PMID: 32671599)
- Black market products labeled as FS344 frequently contain adulterants (e.g., MGF, GHRP-2) rather than follistatin, posing unpredictable safety risks to users. Inherited from Follistatin-344 (PMID: 31758732)
- Potential for serious harm to patients cited in sports medicine review; rigorous human safety data are described as scarce for FS344 and similar unapproved peptides. Inherited from Follistatin-344 (PMID: 41966639)
Contraindications
- Follistatin-344 is prohibited by WADA (Chapter S4). Competitive athletes should check their sport's current anti-doping rules for IGF-1 LR3 as well. Inherited from Follistatin-344 (PMID: 31758732)
- Potential concern in individuals with active malignancy: LR3 IGF-I accelerated tumour growth in a mouse cancer cachexia model despite limiting muscle wasting. Inherited from IGF-1 LR3 (PMID: 31285507)
- Potential concern regarding use in conditions of placental insufficiency or fetal growth restriction: IGF-1 LR3 did not improve growth outcomes and reduced circulating amino acids in FGR fetal sheep. Inherited from IGF-1 LR3 (PMID: 39679943)
- No formal contraindications are stated in the reviewed literature. History of or susceptibility to central serous chorioretinopathy should be considered a potential risk factor given the reported association (PMID: 32671599). Inherited from Follistatin-344 (PMID: 32671599)
- IGF-1 LR3 + Follistatin-344 has not been evaluated as a combination in any clinical trial. The lack of combination-specific contraindications reflects that absence of study, not established safety. No combination study cited in either component file