Bone mineral density and bone acquisition in children and young adults with cystic fibrosis:: A follow-up study

Objective: To investigate bone mineral density and bone homeostasis in cystic fibrosis (CF) and to assess changes in a 2-year period. Methods: Thirty-eight patients with clinically stable CF (11 children, 16 adolescents, 11 young adults) were enrolled. No patient was treated with corticosteroids before or during the study. Weight and height Z scores and bone mineral density (BMD) Z-score at the femoral neck and the lumbar spine were recorded at the beginning of the study and after 2 years. Osteocalcin and cross-link excretion, both measurements of bone turnover were also measured. Correlations between BMD, bone turnover parameters, disease severity, pubertal stage, and nutritional state were calculated. The maternal BMD was also determined and related to that of the child. Results: Height and weight Z scores were normal in children and below normal in adolescents. Puberty was delayed in most patients. Bone age was lower than chronological age in adolescents. Lumbar spine and femoral neck BMD Z scores were below normal in each age group. Disease severity determined by Schwachman score correlated with lumbar BMD (r = 0.45, P < 0.02). BMD Z scores did not change during 2 year follow-up. Maternal and patient lumbar and femoral BMD correlated significantly (r = 0.51, P < 0.01, and r = 0.54 P < 0.01, respectively). Conclusions: Bone deficit is present in patients with CF who have never received steroid treatment. Delay of puberty, chronic inflammation, or genetic susceptibility might be responsible for this phenomenon which was found in patients who had never received steroids and who were in relatively good clinical state.