Creatinine, quantitatively excreted in
the urine, is nonenzymatically formed from intracellular creatine
and phosphocreatine in muscles. The creatinine excretion mainlydepends on total body skeletal muscle mass. Thus the urinary
creatinine concentration has been commonly used to normalize
the concentrations of uric acid and other diagnostic markers in
urine in clinical and biomedical laboratories