Bone mineral status in prepubertal children with cystic fibrosis

Abstract

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. 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. 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. 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.