腫瘍に伴うミネラル代謝異常

Bone and Calcium Abnormalities in Malignancy. Derangements of mineral metabolism associated with tumors.

　骨は，生体の支持や内臓の保護などの硬組織としての機能を有するとともに，血中ミネラル濃度調節にも必須の役割を果たしている。したがって，悪性腫瘍に伴う高カルシウム（Ca）血症や腫瘍性骨軟化症のように，骨代謝異常は血中Caやリン濃度異常を伴うことがある。悪性腫瘍に伴う高Ca血症の代表的惹起因子として副甲状腺ホルモン関連蛋白（parathyroid hormone-related protein：PTHrP）が，また腫瘍性骨軟化症の惹起因子として線維芽細胞増殖因子23（fibroblast growth factor 23：FGF23）が同定された。これらの疾患は，臨床的に重要であることに加え，ミネラルや骨・軟骨代謝調節機序の理解を深める契機ともなった。

　Bone as a hard tissue has several functions such as supporting our body and protecting internal organs. In addition, bone has a pivotal role in the regulation of circulatory mineral concentrations. Therefore, abnormal bone metabolism is sometimes accompanied by deranged serum calcium or phosphate levels as shown in patients with malignancy-associated hypercalcemia（MAH）or tumor-induced osteomalacia（TIO）．Parathyroid hormone-related protein, PTHrP, was cloned as a major humoral factor causing MAH. Similarly, fibroblast growth factor 23, FGF23, was identified as a causative factor for TIO. Therefore, MAH and TIO are not only important in clinical practice but also gave us deep insights into the mechanisms of mineral homeostasis, and bone and cartilage metabolism.