Hydroxyproline/creatinine ratios as estimates of bone resorption in early postmenopausal women. Fasting and 24-h urine samples compared

Abstract

Ratio of urinary hydroxyproline/creatinine excretion is often used as an index of bone resorption. To establish the difference between the fasting urinary content (FU-HPR/CR) and the 24-h urinary excretion (24 h-U-HPR/CR) we determined hydroxyproline and creatinine in specimens from a group of early postmenopausal women. One hundred and eighty-six early postmenopausal women were randomized into 10 groups receiving various doses of sequential female sex hormones and/or 1,25(OH)₂D₃, 0.25 μg per day, or placebo. In all groups there were parallel changes of FU-HPR/CR and 24 h-U-HPR/CR, and in all groups treated with oestrogens the values decreased significantly. The changes in FU-HPR/CR were more pronounced than in the 24-h-U-HPR/CR, which indicates that FU-HPR/CR is a more sensitive marker of changes in bone resorption. The strong correlation between the mean values of 24-h-U-HPR/CR and those of FU-HPR/CR suggests that both methods are convenient for evaluating changes during long-term studies in groups of patients. The correlation on an individual basis is weak. The substantial intraindividual variation in 24-h-U-HPR/CR, (34.6%) indicates that FU-HPR/CR (CV=17.0%) is the more valid variable for individual patients.

Key Words:

• fasting urinary hydroxyproline
• 24-h urinary hydroxyproline
• menopause