Urinary pyridinium collagen cross-links predict growth performance in children with idiopathic short stature and with growth hormone (GH) deficiency treated with GH. Skeletal metabolism during GH treatment.

Abstract

GH is able to promote longitudinal growth in children with GH-deficiency (GHD) and in some children with idiopathic short stature (ISS). The objectives of this study were to evaluate the predictive value of bone and collagen markers on the growth response to GH therapy in children with ISS and with GHD, and to characterize the effects of GH treatment on bone and collagen turnover in children with ISS and with GHD. Twenty prepubertal short, slowly growing, children treated with GH, 15 IU/m2 per week, were studied; of them 13 (10 males) had ISS and 7 (5 males) had GHD. An overnight 12-h urinary collection and a fasting morning blood sample were obtained at baseline, 1, 3, 6, and 12 months of treatment. Urinary levels of collagen cross-links, pyridinoline (Pyd) and deoxypyridinoline (Dpd), and circulating levels of osteocalcin, intact PTH, calcitonin, procollagen type III aminoterminal propeptide (PIIINP), insulin-like growth factor-I, and alkaline phosphatase were determined. Urinary collection was also obtained from 127 healthy children (51 males) aged 6-13 yr. In children with ISS, the changes in Dpd over 1 month of GH therapy were related to the changes in height velocity (HV) over 1 yr of therapy (r = 0.67; P < 0.05); the changes in Pyd after 1 month of GH treatment were related to the changes in HV at 6 months of GH treatment (r = 0.57; P < 0.05). All the other markers evaluated were not related to the HV changes in children with ISS. In children with GHD, the changes in Pyd and in Dpd after 1 month of GH treatment were positively related to the changes in HV after 12 months of therapy (r = 0.82; P < 0.05, and r = 0.82; P < 0.05, respectively). The changes in Pyd after 1 month were also related to the HV changes after 6 months of GH (r = 0.77; P < 0.05). Positive relationships between the HV after 6 months of GH and the increases of PIIINP (r = 0.80; P < 0.05) and osteocalcin (r = 0.77; P < 0.05) after 3 months of GH therapy were observed. All patients showed urinary Dpd and Pyd excretions in the normal range. In patients with ISS, Pyd (P < 0.05), Dpd (P < 0.05), osteocalcin (P < 0.01), PIIINP (P < 0.01), and alkaline phosphatase (P < 0.01) increased longitudinally during the GH treatment and the increments reached a maximum after 3-6 months of therapy. Patients with GHD showed an increase of the same markers but the increases occurred earlier, after 1 month of GH therapy. The collagen cross-links, Pyd and Dpd, could be helpful early markers in predicting the responsiveness to GH therapy in children with ISS and with GHD. GH treatment stimulates bone and collagen metabolism.