Myostatin — 1 mg

Myostatin is growth differentiation factor 8, a member of the transforming growth factor beta protein family. Umbrella Labs describes its listed myostatin material as a recombinant reference protein for studying pathways that limit muscle growth. This identity is important because “myostatin” and “myostatin inhibitor” describe opposite sides of the same experimental system. A vial of the ligand should not be described as blocking the ligand merely because many discussions of the pathway focus on attempts to increase muscle mass.

McPherron, Lawler, and Lee reported in 1997 that disrupting the GDF-8 gene in mice produced markedly increased skeletal-muscle mass, establishing a central role in growth restraint. Schuelke and colleagues subsequently described a child with a myostatin mutation and pronounced muscle hypertrophy, providing human genetic evidence relevant to that biological function. These findings concern deficient or altered myostatin signaling, not the effects of administering the intact protein. The generic product designation also leaves details such as mature ligand versus precursor, species, and molecular assembly to the supplier specification; those characteristics matter when matching a research material to an experimental paper.