3-Methylhistidine Unit Converter

3-Methylhistidine (3-MH) is a modified amino acid that serves as a direct marker of skeletal muscle protein breakdown. It is formed when histidine residues in the contractile muscle proteins actin and myosin are methylated after those proteins have been built.

When actin and myosin are broken down through normal turnover or accelerated catabolism, 3-MH is released into the bloodstream. Because the body cannot recycle it into new proteins, it is excreted unchanged in the urine. This makes its concentration a reliable, stoichiometric measure of myofibrillar protein degradation.

Dietary sources, particularly poultry and fish, also contribute to circulating 3-MH levels. After an overnight fast, roughly 80% of plasma 3-MH reflects endogenous muscle breakdown rather than recent food intake.

3-Methylhistidine is released primarily from skeletal muscle when the contractile proteins actin and myosin undergo normal or accelerated degradation. Dietary meat, especially poultry and fish, is the main exogenous source.