MOLECULAR INFORMATION
Molecular information
- Type
- Modified insulin-like growth factor 1 · long Arg3 substitution increases serum half-life
IGF-1 LR3 is a modified insulin-like growth factor 1 sold heavily in bodybuilding circles.
Claims vs evidence
- Muscle growth / hypertrophy — extrapolated from IGF-1 biology, no adequately-powered human RCT in performance use
- Recovery / wound healing — preclinical animal data
- Anti-ageing — speculative
Why we grade it D
The mechanism is real (IGF-1 is a well-characterised growth factor), but the marketed use case has no RCT support, the safety profile is unfavourable at the doses used recreationally, and no sponsor is pursuing performance authorisation.
Frequently asked questions
- What is IGF-1 LR3?
- An analogue of insulin-like growth factor 1 modified by an N-terminal extension and an arginine-3 substitution. The modification slows IGFBP binding and extends the in-vivo half-life from minutes to several hours.
- Is IGF-1 LR3 authorised?
- No — no clinical authorisation in any major market. Authorised IGF-1 products (Increlex / mecasermin) are unmodified recombinant IGF-1, used for severe primary IGF-1 deficiency under strict specialist control. The "LR3" modified version is grey-market.
- Is it safe?
- Documented risks include hypoglycaemia (insulin-receptor cross-reactivity at supraphysiologic doses), acromegalic features with chronic use, and theoretical cancer-promotion concerns via the IGF-1 / IGF-1R axis. WADA-prohibited in sport.