Renal excretion of cystathionine and creatinine in humans at different ages.

The renal excretion of cystathionine is not age-dependent when related to body surface. Regarding the urinary creatinine concentration as reference, the excretion of cystathionine in adults is lower than in infants and children. However, this is probably due to a higher urinary concentration of creatinine in adults compared to that in children. Premature infants excrete more cystathionine in their urine than mature infants. The same is true for premature infants on a methionine-enriched formula compared to premature infants on a low methionine formula.