Effect of growth hormone treatment on calcium kinetics in patients with osteogenesis imperfecta type III and IV

Using a dual stable isotope technique, the effect of growth hormone (GH) on whole body calcium (Ca) metabolism was studied in children (ages 5-14 year s) with type III (n = 9) and IV (n = 8) osteogenesis imperfecta, Each subje ct was studied twice: at baseline and following a GH (0.1-0.2 U/kg per day) treatment period of 1-1.5 years. Subjects were given Ca-42 intravenously a nd Ca-44 orally. The sera and urine Ca-42 and Ca-44 isotopic enrichments we re followed over 7 days using thermal ionization mass spectrometry, The SAA M program was used to fit a three-compartment model to the tracer data. No significant differences were observed between: (1) children with type III a nd IV disease; or (2) baseline studies of boys and girls within each diseas e type. However, GH treatment significantly increased: (1) the exchangeable calcium pool (EP) in type III patients (2086 vs. 4422 mg/day, p 0.02); and (2) the parameter associated with bone calcium accretion in type IV patien ts (Vo(+): 973 vs. 1560 mg/day, p = 0.03) with boys responding with a signi ficantly greater increase than girls (p = 0.008). Although not statisticall y significant, a trend toward an increase in Vo(+) in type III patients and in EP in type IV was observed following treatment. Our observations imply that more Ca was available for bone mineralization following GH treatment i n these subjects. (C) 1999 by Elsevier Science Inc. All rights reserved.