The aim of the study was the evaluation of plasma osteocalcin (O.), alkaline phosphatases (A.P.) and urinary hydroxyproline excretion (uOHPr) in subjects 3-20 years aged. O., A.F. and uOHPr were increased in patients less than 15 years aged; thereafter the values were similar to normal adult values. O. correlates with age and body surface area in children aged less than 15 years; the highest values were observed at the expected age of puberal spurt. This behaviour was not evident for the other bone turnover markers studied. In conclusion, it could be suggested that O. is a useful index of bone peak mass reached at puberty
