Peptides
IGF-1 LR3: what the research actually shows
How does it work?
IGF-1 LR3 is a modified insulin-like growth factor 1 analogue designed to bind less strongly to IGF-binding proteins. That can change its availability to tissues. It is biologically distinct from prescription recombinant human IGF-1 (mecasermin), so evidence and labeling for mecasermin cannot simply be transferred to LR3. [1]
What do studies show?
In a controlled rat experiment, LR3-IGF-I had stronger effects than native IGF-I on nitrogen retention and other growth-related measures under the study conditions. These were catheter- or pump-delivered animal exposures in a catabolic model, not a human training trial. There is no verified randomized human study showing that injected IGF-1 LR3 builds muscle, speeds recovery, or reduces body fat in healthy adults. [1]
Safety
The lack of human LR3 studies leaves adverse-event rates, long-term risks, and product quality uncertain. Because it acts on growth and glucose-regulating pathways, low blood sugar and effects on unwanted tissue growth are plausible concerns, but human LR3 risk cannot be quantified from this evidence. Tested athletes should also check the current WADA Prohibited List, which covers IGF-1 and its analogues. [2]
DOSE STATUS
How much?
EVIDENCE CONTEXT
Why?
The cited evidence does not establish a dose for this use or product.
No effective and safe adult dose of IGF-1 LR3 has been established in clinical trials. Jay Campbell cites an anecdotal protocol from Hunter Williams of 50 mcg subcutaneously in the morning or before training, with 20 mcg as an initial amount. This is a description of an educator’s practice, not a study-backed or medically recommended dose. The rat study does not validate that schedule, and a 1 mg vial does not establish purity or suitability for human use. [1,3]