Background
Cystic Fibrosis Bone Disease (CFBD) is one of the endocrine complications of cystic fibrosis (CF). Contributing pathophysiological mechanisms are decreased osteoblast activity and maturation, malabsorption of vitamins, malnutrition, lack of exercise, late puberty and the use of exogenous glucocorticoids during disease exacerbation.
Aim
We aimed to determine prevalence and risk factors for low bone mineral density (BMD) in children with CF.
Methods
Anthropomorphic and endocrine data were collected in all children with CF aged 8-18 years, visiting the outpatient clinic in the CF expertise center UMCU from 2018 – 1st November 2021. DEXA-scans were performed using the Hologix DXA scan.
Analyses were performed using the T-test for equality of means, Pearson’s correlation and the ANOVA-test.
Results
Eighty-nine children (46 boys, 43 girls) were enrolled, with a mean age of 13.3 ± 3.1 yrs in boys and 12.7 ± 2.8 yrs in girls. Most children (64.0%) had the homozygous dF508 mutation. Cystic fibrosis related diabetes was present in 18.0% and cystic fibrosis related liver disease in 24.7% of the children.
Mean BMD SDS in lumbar spine (LS) and total body less head (TBLH) (n = 88) were -0.31 ± 1.23 and -0.32 ± 1.04 respectively. Mean body mass index (BMI) SDS was 0.0002 (n=85).
BMI SDS was positively correlated with BMD SDS in LS and TBLH (r=0.457, p<0.001 and r = 0.370, p = 0.001). Boys with low BMD SDS (< -2) had significantly lower BMI SDS when compared to boys with BMD SDS > -2. This difference was not found in girls.
In total, seven children (8%, 4 boys, 3 girls) had low BMD SDS. Of the 89 children, 42 had 25(OH)D deficiency. Children with low BMD SDS (<-2) did not have significantly different lower mean 25(OH)D levels when compared to children with normal BMD SDS.
Conclusion
BMD in children with CF seems to be normal in most cases, despite 25(OH)D deficiency in almost 50%. To ensure optimal BMD in children with CF, especially in boys, BMI control and- to some extent,- 25(OH)D remain important cornerstones.