3-Methylhistidine (3-MH) is a post-translationally modified amino acid which is excreted in human urine.[1] Urinary concentration of 3-methylhistidine is a biomarker for skeletal muscle protein breakdown in humans who have been subject to muscle injury.[2] [3] Urinary 3-methylhistidine concentrations are also elevated from consumption of soy-based products and meat, particularly chicken.[4]
3-Methylhistidine is a metabolic product that is produced in the body via the enzymatic methylation of histidine during peptide bond synthesis and the methylation of actin and myosin.
The normal concentration of 3-methylhistidine in the urine of healthy adult humans has been detected and quantified in a range of micromoles per millimole (μmol/mmol) of creatinine, with most studies reporting the average urinary concentration between 15–20 μmol/mmol of creatinine. The average concentration of 3-methylhistidine in human blood plasma has been detected and quantified at 2.85 micromolar (μM) with a range of μM. The average concentration of 3-methylhistidine in human cerebrospinal fluid (CSF) has been detected and quantified at 3.82 μM with a range of μM.