Abstract
N-terminal propeptide of type I procollagen (PINP) is a marker of newly formed type I collagen. However, its role in hypophosphatemic rickets/osteomalacia has not yet been established. Metabolic bone markers were examined in patients with oncogenic osteomalacia (OOM) and X-linked hypophosphatemic rickets (XLH), and in healthy controls. OOM and XLH patients were found to have hypophosphatemia secondary to elevated levels of serum fibroblast growth factor 23 (FGF-23). OOM patients had reduced levels of 1,25-dihydroxy vitamin D (1,25D) compared with XLH patients and healthy controls, despite attenuation of the reduction in these levels in the XLH patients secondary to active vitamin D supplementation. In contrast to patients with XLH, OOM patients showed a significant increase in serum PINP, which is suggestive of accelerated bone matrix formation. Bone alkaline phosphatase (BAP) and the BAP/PINP ratio were also increased in OOM but not in XLH patients, suggesting the presence of a disturbance in bone mineralization in OOM. Long-term supplementation of active form vitamin D and inorganic phosphate (IP) may have attenuated the defect in bone mineralization in the XLH patients, resulting in the normalization of PINP, BAP, and the BAP/PINP ratio. The present results suggest that, as with BAP, PINP is an appropriate metabolic bone marker in the assessment of hypophosphatemic rickets/osteomalacia.
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Acknowledgments
The authors are grateful to Fujirebio Inc. for their technical assistance in the measurement of serum PINP. This study was supported by two Grants-in-Aid for the Scientific Research (C) (20591101 and 20590980), and a grant from The Kidney Foundation, Japan (JKFB11-9).
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All participants provided written informed consent before inclusion. This study was approved by the ethics committee of the Osaka City University Graduate School of Medicine and was conducted in accordance with the principles of the Declaration of Helsinki.
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The authors declare that they have no conflict of interest.
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Nagata, Y., Imanishi, Y., Ishii, A. et al. Evaluation of bone markers in hypophosphatemic rickets/osteomalacia. Endocrine 40, 315–317 (2011). https://doi.org/10.1007/s12020-011-9512-z
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DOI: https://doi.org/10.1007/s12020-011-9512-z