Increased urinary excretion of collagen crosslinks in girls with Ullrich-Turner syndrome.

Skeletal abnormalities and "osteoporosis" are frequent features of Ullrich-Turner syndrome (UTS), but their cause remains largely unknown. In this study, we compared the urinary excretion of hydroxyproline (OHP), pyridinoline (PYD) and deoxypyridinoline (DPD) in 28 girls (bone age 3.5-11.0 years, mean 7.4 years) with UTS and 30 healthy prepubertal children (chronological age 3.9-10.9 years, mean 7.6 years). Expressed relative to the square of the height, the excretion of both collagen crosslinks was significantly higher in UTS than in controls (23.4% for PYD, 33.6% for DPD, p < 0.05). In contrast, no significant difference was found for OHP. The molar PYD/DPD ratio was significantly lower in UTS children than in controls (mean (+/- SD) 3.4 (+/- 0.41) versus 3.8 (+/- 0.55); p = 0.004). While the higher excretion of collagen crosslinks reflects enhanced bone resorptive activity in UTS, the lower PYD/DPD ratio might be due to structural alterations in collagen.