All Natural Hormone Hacks for Muscle Growth & Fat Loss: T, HGH, Cortisol, IGF 1, Insulin, T3 & More! If your priority is building muscle, IGF 1 is what really matters. IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society CJC 1295 + Ipamorelin vs IGF 1 LR3 for Muscle Growth IGF 1 LR3 forces receptor desensitization in 4 6 weeks, requiring months off before you can use it again. CJC 1295 and Ipamorelin amplify your natural What is IGF 1 LR3?, Insulin Like Growth Factor 1 Long R3 (IGF 1 LR3) is a modified version of IGF 1 with a longer half life, making it significantly more potent and effective for muscle growth,