Normal value: Small amounts of aminoacids, both free and combined, are excreted in the urine.
The free aminoacid amounts to about 1.4mg/kg for women.
Age and Sex: Normal adult women excrete more aminoacids. There is some evidence for the existence of individual patterns of aminoacids excretion. One person tends to excrete more of one aminoacid and less of another than does another person.
The sex difference does not hold for children, who excrete somewhat less than adults; infants and prematurely born babies excrete about four times as much per kg as do older children.
Growing children excrete higher levels of hydroxyproline than do adults, reflecting an increased metabolism of collagen.