Bone mineral status in prepubertal children with cystic fibrosis

Objectives: To determine whether osteopenia is evident in prepubertal children with cystic fibrosis (CF) and, if so, whether it is caused by a deficiency in bone formation or increased bone resorption. Study design: With the use of a prospective case control study design, we investigated 11 prepubertal children with CF between the ages of 8 and 12 years old and a non-CF control group matched by weight and sex. Bone density at the radius, ulnar, trochanter, femoral neck, and lumbar spine, biochemical markers of bone metabolism, calcium, vitamin D metabolites,and intact parathyroid hormone were measured in all subjects. Comparisons between the 2 groups were performed with Wilcoxon matched pairs and Fisher exact tests. Results: Intake of total calories, calcium, phosphorus, and vitamin D was significantly greater in the CF group than in the control group. Serum 25(OH)vitamin D levels were significantly lower in the CF group: median 22 ng/mL for the CF group and 39 ng/mL for the control group (P = .02). 1,25(OH)(2) vitamin D levels were borderline or low in 7 subjects in the CF group and 2 members of the control group (P = .08, Fisher exact test). Intact parathyroid hormone levels were higher than the upper limit of normal in 4 subjects of the CF group and 1 member of the control group. Despite these biochemical abnormalities, we found no evidence of bone mineral deficiency in the CF group. Conclusions: Prepubertal children with CF do not have bone mineral deficit compared with a weight- and sex-matched control group; however, their lower vitamin D levels may portend problems with bone mineralization during adolescence and adulthood.