Bone mineral content in cystic fibrosis patients: correlation with fat-free mass

To assess the bone mineral content in well nourished patients with cystic fibrosis and to seek a correlation with fat-free mass.

Fourteen cystic fibrosis patients aged 6 to 20 years were studied and compared to 14 healthy controls matched for gender, age, and nutritional status. Bone mineral content was determined by dual energy x ray absorptiometry (DEXA).

Nutritional inquiry showed higher ingestion of macronutrients and micronutrients by cystic fibrosis patients than by controls. Mean whole skeleton bone mineral content was 1.184 (SD 0.536) kg in cystic fibrosis patients and 1.229 (0.576) kg in controls (p = 0.84). Mean lumbar spine bone mineral content was 0.031 (0.013) kg and 0.031 (0.016) kg, respectively (p = 0.99). Anthropometry, bioelectrical impedance analysis, and DEXA showed that fat-free mass was similar in the two groups. Bone mineral content was strongly correlated to fat-free mass. Mean blood calcium, phosphorus, serum 25-hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), and osteocalcin were similar in both groups.

Bone mineral content and body composition are normal in a well nourished young cystic fibrosis population. Osteopenia previously reported in cystic fibrosis patients probably has nutritional origins and is therefore not related to a primary defect in bone mineral metabolism.