IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society Organ weights in response to Long R3 insulin like growth factor 1 (LR3 Download Scientific Diagram IGF 1 LR3 (Insulin like Growth Factor 1 Long R3) is often called the "Holy Grail" of muscle building peptides because of its potent anabolic effects. In a Med Spa context, it is typically sought out IGF 1 LR3 in Aesthetic and Anti Aging Medicine: Benefits and Risks Hubmed LONG R IGF I