[Urinary excretion of 3-methylhistidine. Value and application to the study of protein catabolism].

The urinary excretion of 3-methylhistidine (3 MH) is considered an easy and reliable method to quantify muscle protein catabolism in man. The 3 MH/creatinine (Cr) ratio is thought to be a good index of fractional degradation of muscle fibre protein. In the present article, the stress is placed on the limitations of 3 MH assays an- on their clinical applications. In thyroid diseases and in malnutrition (anorexia nervosa), the 3 MH/Cr ratio differentiates clearly marasmic malnutrition without increase in protein catabolism from hypercatabolic states, such as hyperthyroidism, with excessive protein degradation. 3 MH measurements therefore appear to be useful to determine the contribution of protein catabolism to lean mass reduction.