Blood levels and urinary excretion of tyrosine were determined in 31 low-birth-weight infants. Fourteen of these infants were preterm and 17 were born at term. Gestational age was assessed by menstrual history, and doubtful cases were corrected by neurological examination. Both plasma and urinary tyrosine levels were markedly increased in infants whose gestational age was below 38 weeks. These differences were present regardless of the infant's birth weight. Thus, the changing pattern of tyrosine metabolism, previously described, is a phenomenon associated with maturity and not with birth weight. These data supply a practical biochemical method for assessing gestational age in low-birth-weight infants.
Rizzardini M, Abeliuk P. Tyrosinemia and Tyrosinuria in Low-Birth-Weight InfantsA New Criterion to Assess Maturity at Birth. Am J Dis Child. 1971;121(2):182–185. doi:10.1001/archpedi.1971.02100130136019
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