M. Worsfold et al., Age-related changes in body composition, hydroxyproline, and creatinine excretion in normal women, CALCIF TIS, 64(1), 1999, pp. 40-44
We have made a cross-sectional study of relationships among age, whole body
bone mineral content (WBBMC), and non-bone lean body mass (NBLBM) measured
by dual energy X-ray absorptiometry (DXA), and daily excretion of hydroxyp
roline (OHP) and creatinine (Cr) in a group of normal women. WBBMC fell wit
h age from the 6th decade, whereas NBLBM was almost constant. Creatinine ex
cretion fell with age from the 5th decade until the 9th, to a much greater
degree than NBLBM, reaching a nadir in the 8th decade. Daily excretion of h
ydroxyproline showed a peak in the 6th decade and fell moderately thereafte
r. The greater fall of creatinine compared with hydroxyproline resulted in
rising OHP/Cr ratios with advancing age, in contrast to the pattern of hydr
oxyproline excretion. The use of creatinine as a correction for urine dilut
ion or fur lean body mass (LBM) in assays for markers of bone turnover must
therefore be viewed with caution.