Myostatin-related muscle hypertrophy

Myostatin-related muscle hypertrophy is a rare genetic condition characterized by reduced body fat and increased skeletal muscle size.^[1] Affected individuals have up to twice the usual amount of muscle mass in their bodies, but increases in muscle strength are not usually congruent.^[2] Myostatin-related muscle hypertrophy is not known to cause medical problems, and affected individuals are intellectually normal. The prevalence of this condition is unknown.

Mutations in the MSTN gene cause myostatin-related muscle hypertrophy. The MSTN gene provides instructions for making a protein called myostatin, which is active in muscles used for movement (skeletal muscles) both before and after birth. A 2010 research paper in the Journal of Musculoskeletal & Neuronal Interactions, which was discussed outside of academic circles,^[3] linked myostatin to muscle mass and bone structure.^[4] This protein normally restrains muscle growth, ensuring that muscles do not grow too large. Mutations that reduce the production of functional myostatin lead to an overgrowth of muscle tissue. Myostatin-related muscle hypertrophy has a pattern of inheritance known as incomplete autosomal dominance. People with a mutation in both copies of the gene in each cell (homozygotes) have significantly increased muscle mass. People with a mutation in one copy of the MSTN gene in each cell (heterozygotes) also have increased muscle bulk but to a lesser degree.

The effect of this growth factor was first described in cattle as bovine muscular hypertrophy by the British farmer H. Culley in 1807. Cattle that have a myostatin gene deletion look unusually and excessively muscular.