A reduction in bone-formation indices (serum bone-specific alkaline phosphatase, OC, P1NP) and an increase in bone-resorption indices (CTX and urine N-terminal telopeptide of type 1 collagen) has been observed in patients with CF, especially during infections, but currently there are no recommendations on their use in patients with CF [52]. This evidence concerns the gene BGLAP and cystic fibrosis.