A fusion protein comprising at least one IGF1 variant component and a fusion component (F), and, optionally, a signal sequence, exhibiting improved stability relative to the native IGF1 or IGF2 polypeptide. The fusion component (F) may be a multimerizing component, a targeting ligand, or another active or therapeutic compound. IGF1 variants were shown to have improved ability to induce skeletal muscle hypertrophy relative to native IGF1.