A Study on Urinary Hydroxyproline: Creatinine Ratio of Normal Japanese at Various Age

Abstract

It is necessary to confirm the normal values of urinary hydroxyproline by age and sex, for the sake of estimating a dose-response relationship between urinary hydroxyproline and various independent variables just like growth, exposure to NO2, collagen diseases and so on. Expression of the hydroxyproline excretion as the hydroxyproline: creatinine ratio has made urinary hydroxyproline excreted in random specimens possible to be a representative of hydroxyproline excreted per 24 hours specimen, thus eliminating the burdensome collection of 24 hours specimens. And the stability of specimen was also studied and it has been confirmed that urinary hydroxyproline is not influenced if it is treated with addition of 0.01% toluene and stored under -20°C. The urinary hydroxyproline excretion from normal Japanese ranging from three years to seventy years of age has been expressed as milligrams hydroxyproline to milligrams creatinine excreted at random specimens. Number of subjects in this was 3, 188 (male-1, 511 and female-1, 677). At all ages the ratio is almost equivalent in both sexes but the ratio in female was relatively higher than the ratio in male during from eight to twelve years of age. The ratio rapidly decreases from three to seven years of age and increases from seven to nine or ten years of age and after that, it decreases to about twenty gradually. According to the results of Allisons' study, the ratio decreases from six months about five years of age and after remaining constant puberty, it decreases again to about age twenty. Such a difference between Allisons' study and our results possibly suggests the characteristic of growth in school-children in Japan. Subsequently, Allison points out that the ratio remains constant through age seventy yeas and in spite of that, our study suggests that even after 20 years of age, the ratio still shows a slight decrease by aging, as a result of mass examination. In conclusion, although it is a fact that the ratio rapidly decreases from 3 years to seven years of age from a micro-view point, there are acontinuous decrease in the ratio from 3 years to 70 years of age by aging, if it is overlooked through a whole human life.