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Low serum bone gamma-carboxyglutamic acid protein concentrations in patients with cystic fibrosis: correlation with
J De Schepper1, J Smitz, I Dab
1Department of Pediatrics, Akademisch Ziekenhuis VUB, Brussels, Belgium.
Insights
In children with cystic fibrosis (CF), low serum bone gamma-carboxyglutamine acid (GLA) protein (BGP) was common, but not a reliable predictor of osteopenia. Further research is needed to understand bone health in CF patients.
Area of Science:
- Pediatric Endocrinology
- Bone Metabolism
- Genetic Disorders
Background:
- Cystic Fibrosis (CF) is a genetic disorder affecting multiple organs, including bones.
- Bone mineral density (BMD) is often compromised in children and adolescents with CF.
- Serum bone gamma-carboxyglutamine acid (GLA) protein (BGP) is a marker of bone turnover.
Purpose of the Study:
- To investigate serum BGP levels in pediatric CF patients.
- To assess the relationship between serum BGP, BMD, and other clinical factors in CF.
- To evaluate the utility of serum BGP as a predictor of osteopenia in CF.
Main Methods:
- Radioimmunoassay was used to measure serum BGP concentrations in 31 children and adolescents with CF.
- BMD was assessed at the lumbar spine.
- Correlation with growth velocity, lung disease severity, and hormonal levels was analyzed.
Main Results:
- Median serum BGP Z-score was -1.72, with 42% of patients showing decreased levels.
- Decreased BGP was not linked to hormonal levels, growth velocity, or lung disease severity.
- Five out of six patients with decreased BMD also had decreased BGP, indicating low specificity (72%) for predicting osteopenia.
Conclusions:
- Reduced serum BGP concentration is prevalent in pediatric CF patients.
- Serum BGP is not a reliable standalone predictor of osteopenia in this population.
- Further investigation into bone health markers and interventions in CF is warranted.
Abstract:
In 31 children and adolescents with cystic fibrosis (CF), whose bone mineral density (BMD) was determined at the level of the lumbar spine, serum bone gamma-carboxyglutamine acid (GLA) protein (BGP) was measured. A standard radioimmunoassay method gave for the studied CF population a median serum BGP concentration of 9 micrograms/l (range: 0.8-18.6) which corresponds to a median Z-score for age of -1.72 (range: -3.3 to +0.04). Thirteen patients presented a BGP concentration lower than 2 standard deviations (SD) under the mean for age. These patients did not differ from the others by their circulating thyroxine, triiodothyronine, 25-hydroxyvitamin D or parathyroid hormone levels. The lowering of the BGP concentration was neither related to the growth velocity nor to the severity of the lung disease, as assessed by lung scintigraphy. Six patients with a decreased BMD (< 2 SD under mean for age) were found. Five of them had also a decreased BGP concentration. In conclusion, decreased serum BGP concentration was found in 42% of the studied CF patients and could not be related to hormonal abnormalities. Serum BGP had a low specificity (72%) in predicting osteopenia in young CF patients.