$MYOS MYOS’ proprietary all natural ingredient clinically proven to increase muscle size, lean body mass and strength. Fortetropin is a bioactive proteo-lipid complex composed of about > 250 proteins, > 50 lipids, a variety of peptides and other bioactive molecules isolated at a specific stage of development from fertilized egg yolk using a proprietary process that retains the biological integrity and bioactivity of the mixture.