Urinary excretion of endogenous hydroxyproline by normal male infants.

Abstract

Extract: Rates of urinary excretion of total hydroxyproline by 38 normal fullsize male infants were determined on 176 occasions. Each urine collection period was 72 hours. When the period of urine collection was begun between the fourth and eighth day of life, mean rate of excretion was 30.6 mg/day (standard deviation 6.9 mg/day). Maximal rates of urinary excretion were observed between 21 and 60 days of age (mean: 48.1 mg/day; standard deviation 9.7 mg/day). Between 121 and 582 days of age, mean rate of excretion had decreased slightly to 43 mg/day. Eleven infants were each studied on at least five occasions between 20 and 120 days of age. Mean rate of urinary excretion of hydroxyproline by each infant was shown to be significantly correlated with rate of gain in length but not with rate of change in weight or surface area. Speculation: During normal infancy it seems probable that a major proportion of the hydroxyproline excreted in the urine is derived from collagen of bone. Rate of excretion probably parallels rate of bone growth. Thus, any disorder that depresses the normal rate of linear growth is likely to result in sharp diminution of urinary excretion of hydroxyproline. Such a biochemical index of growth may be clinically useful.