Influence of growth hormone on a new marker of cartilage metabolism (Chondrex)

The aim of this study was to evaluate the usefulness of a major secretory protein of human chondrocytes (chondrex) as a potential serum marker of bone responsiveness to growth hormone (GH). The study included 18 children (10 F, 8 M), aged 10.9 ± 2.3 years, bone age 8.8 ± 2.7 years, height -2.3 ± 0.22 SDS, affected by isolated idiopathic GH deficiency (GHD). Serum samples for evaluation of chondrex, total, and bone alkaline phosphatase were taken before and 3 and 6 months following treatment with rhGH. The basal serum level of chondrex did not differ between patients (37 ± 22 ng/ml) and controls (33 ± 9.8 ng/ml). Following 6 months of treatment with rhGH, a significant increase of height velocity SDS (from -2.8 ± 0.5 to 1.3 ± 0.7), total (from 195 ± 47 to 264 ± 79 U/liter) and bone alkaline phosphatase (from 81 ± 21 to 108 ± 30 U/liter) was observed, while chondrex serum level remained unchanged (from 37 ± 22 to 36 ± 29 ng/ml). It was concluded that chondrex cannot be considered a reliable marker of bone responsiveness to GH in the growing child.