IGF 1 LR3 + MASS Cycle = CRAZY Growth? #askDave Your doctor checks testosterone. Maybe thyroid. They skip the one marker that actually tells you how your body is building, recovering, and aging. It's called IGF 1. Most men have never seen their Insulin like growth factor 1 promotes cell cycle progression via upregulation of cyclin D1 expression through the phosphatidylinositol 3 kinase nuclear factor B signaling pathway in FRTL thyroid cells Acta Pharmacologica Sinica Recombinant Human IGF I IGF 1 Protein, CF 291 G1: R&D Systems Late life targeting of the IGF 1 receptor improves healthspan and lifespan in female mice Nature Communications