Calcium Kinetics in Children with Osteogenesis Imperfecta Type III and IV: Pre- and Post-Growth Hormone Therapy

• Published in: Calcified tissue international Vol. 67; no. 2; pp. 97 - 100
• Main Authors: Vieira, N E, Goans, R E, Weiss, G H, Hopkins, E, Marini, J C, Yergey, AL
• Format: Journal Article
• Language: English
• Published: 01.08.2000
• ISSN: 0171-967X
• DOI: 10.1007/s002230001110

Children with osteogenesis imperfecta (OI) type III and type IV were studied using a super(42)Ca stable isotope technique. Serum dilution kinetics of super(42)Ca were studied pre- and post-growth hormone (GH) treatment in 9 OI III (age range 5-9 years) and 8 OI IV patients (age range 5-12 years). Each subject was studied twice: at baseline and following GH therapy (range 1-1.5 years). Isotopic enrichments of super(42)Ca were followed over 7 days using thermal ionization mass spectrometry. A binding site model, which describes reversible and irreversible binding of calcium (Ca) ions to postulated short- and long-term binding sites in bone, was used to analyze the kinetic data. In type III patients, GH treatment (1) increased the fraction of short-term binding sites, theta (0.777 + 0.112 versus 0.877 + 0.05, respectively; P 0.034); (2) increased the apparent half-life of a Ca ion attached to the long-term binding site by 76% (P 0.009); (3) although not statistically significant (P 0.098), a trend toward an increased growth rate was observed with increasing change in theta ( Delta theta ); (4) patients experienced a 75% increase in growth rate during the first 6 months of treatment. In type IV patients, GH treatment increased the apparent half-life of a Ca ion attached to the long-term binding site by 83% (P 0.048), however, no trend toward an increased growth rate was observed with increasing Delta theta in these patients. These significant changes in Ca binding to bone may influence growth in type III patients.