Urinary free deoxypyridinoline levels during childhood

Free urinary deoxypyridinoline (DPD) levels, corrected for the urinary concentration of creatinine (nmol/mmol), were determined in 144 healthy children (76 males and 68 females, mean age +/- SE: 9.1 +/- 0.2 yr, age range: 5.1-14.0 yr) in order to detect the possible age-related changes of this reliable index of bone resorption activity and the relationship between free DPD, gender and pubertal development. Multiple regression analysis revealed that most of the variation in DPD levels was explained by chronological age (coefficient: 2.89, p < 0.02), whereas sex and pubertal stage did not add significance to the variance. Urinary DPD levels were similar in males (24.7 +/- 1.8 nmol/mmol urinary creatinine) and females (24.2 +/- 2.0 nmol/mmol urinary creatinine) and significantly higher (p < 0.02) in pubertal (Tanner stage II-V: 28.6 +/- 2.8 nmol/mmol urinary creatinine) than in prepubertal children (22.4 +/- 1.4 nmol/mmol urinary creatinine), both in males and in females. The pattern of DPD levels was clearly different between females and males, the maximum increase being evident at Tanner stage II-III (mid-puberty) in females and at Tanner stage IV-V (mid-late puberty in males. The increase of DPD paralleled the elevation of urinary GH (pmol/mmol urinary creatinine), a non-invasive and acceptable index of physiological GH secretion, observed during the pubertal growth spurt. The progressive increase of urinary GH in older children was not followed by a further stimulation of bone resorption. Although the relationships between urinary, GH and DPD need to be better investigated, it seems plausible to hypothesize that the determination of urinary free DPD, as a marker of GH action on bone, might have some potential in the follow-up of growth promoting treatments, such as GH.