Monitoring of free and total urinary pyridinoline and deoxypyridinoline in healthy volunteers: sample relationships between 24-h and fasting early morning urine concentrations.

Twelve healthy adults, six men and six women, with no history of bone or joint disease, were studied. They provided 24-h urine samples once weekly, five times, and a 24-h collection including the first sample of the early morning urine (FU). The urinary concentrations of free and total pyridinoline (HP) and deoxypyridinoline (LP), measured during the experimental period, showed no remarkable changes and gave good statistical correlations, particularly LP. Thus, in order to simplify and shorten the analytical procedure and the collection of biological samples, the only measurement of free fraction of HP and LP excreted in FU sample urine could be justified for both diagnostic and epidemiological purposes.