Short-term changes in bone formation markers following growth hormone (GH) treatment in short prepubertal children with a broad range of GH secretion.

OBJECTIVES: Growth hormone (GH) promotes longitudinal growth and bone modelling/remodelling. This study investigated the relationship between levels of bone formation markers and growth during GH treatment in prepubertal children with widely ranging GH secretion levels. METHODS: The study group comprised 113 short prepubertal children (mean age ± SD, 9·37 ± 2·13 years; 99 boys) on GH treatment (33·0 ± 0·06 µg/kg/day) for 1 year. Blood samples were taken at baseline and 1 and 2 weeks, 1 and 3 months, and 1 year after treatment start. Intact amino-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BALP) and osteocalcin were measured using an automated IDS-iSYS immunoassay system. RESULTS: Intact amino-terminal propeptide of type I procollagen (PINP), BALP and osteocalcin, increased in the short-term during GH treatment. PINP after 1 week (P = 0·00077), and BALP and osteocalcin after 1 month (P < 0·0001 and P = 0·0043, respectively). PINP levels at 1 and 3 months correlated positively, and osteocalcin levels at 1 week and percentage change after 1 month correlated negatively, with first year growth response. No significant correlations were found between BALP and first year growth. Multiple regression analysis showed that bone marker levels together with auxological data and insulin-like growth factor binding protein-3 explained the variation in first year growth response to 36% at start, 32% after 2 weeks and 48% at 3 months. CONCLUSION: Short-term increases in levels of the bone formation markers PINP, BALP and osteocalcin showed different temporal patterns, but all correlated with first year growth response during GH treatment. These markers may be a useful addition to existing prediction models for growth response.