Measurements of whole body retention of diphosphonate and other indices of bone metabolism in 125 normals: dependency on age, sex and glomerular filtration.

Measurements of 24-h whole body retention of 99m-Tc-MDP (WBR) has been performed in 125 normal volunteers, together with determinations of serum alkaline phosphatase, urinary hydroxyproline excretion and creatinine clearance. WBR decreased slightly from the 3rd to the 4th decade, after which it increased gradually in the older age-groups. Serum alkaline phosphatase followed an identical pattern, while the urinary hydroxyproline excretion demonstrated a marked but temporary rise in the post-menopausal age-groups. Finally, the creatinine clearance decreased gradually in the older age groups. Analysis of variance demonstrated that WBR varied independently with serum alkaline phosphatase and creatinine clearance, while no relationship between WBR and the hydroxyproline excretion was found. It seems likely that the increasing retention of diphosphonate in elderly persons reflects rising osteoblastic activity as well as decreasing glomerular filtration.