Effect of age on homovanillic and 4-hydroxy-3-methoxymandelic acid levels in plasma

The plasma levels of homovanillic and 4-hydroxy-3-methoxymandelic acids have been determined in 524 normal subjects ranging from birth to 49 years of age using a mass fragmentographic method. The mean concentration of homovanillic acid in plasma declines exponentially from the age of 1 day (X = 2342.0 nmol/l, 426.6 ng/ml) to adulthood (X = 60 nmol/l, 10.9 ng/ml). 4-Hydroxy-3-methoxymandelic acid behaves in a similar although not so extreme manner (392 nmol/l, 77.6 ng/ml-50 nmol/l, 10 ng/ml).