ビタミンＤ不足・欠乏症の臨床的意義と治療

Disorders of Phosphate Metabolism. Vitamin D insufficiency/deficiency：its clinical significance and treatment.

　ビタミンD不足・欠乏症は，体内のビタミンD貯蔵量が減少した状態であり，ビタミンD作用障害の原因として最も頻度が高い。重症のビタミンＤ非充足状態であるビタミンＤ欠乏症は，くる病・骨軟化症の原因となる。一方，軽症のビタミンＤ不足でも，続発性副甲状腺機能亢進症，骨折リスクの増大，さらに骨粗鬆症治療薬への反応低下などを介して，骨の健康を損なう原因になる。本症の診断は，血清25（OH）D濃度を測定しない限り不可能であるが，本邦では2015年現在保険適用がない。現在，本邦でも，本症の診断ガイドラインを策定中であり，血清25（OH）D 20 ng/mL未満をビタミンD欠乏，20 ng/mL以上30 ng/mL未満をビタミンD不足とする方向で試案が公表されている。

　Vitamin D insufficiency/deficiency, a medical condition in which vitamin D store is decreased, is the most frequent cause of decreased action of vitamin D. Severer form vitamin D deficiency can cause hypocalcemia and rickets/osteomalacia. Milder form vitamin D insufficiency also harms bone health via secondary hyperparathyroidism, the increase in fracture risk, and poor responses to anti-osteoporotic medications. Diagnosis can only be made by measuring serum 25（OH）D, which is not currently covered by the Japanese health insurance policy. In Japan, the guideline for the diagnosis vitamin D insufficiency/deficiency is in the process of drafting. According to the current provisional guideline draft that was made in public, vitamin D deficiency would be defined by serum 25（OH）D level less than 20 ng/mL whereas vitamin D insufficiency would refer to the state in which serum 25（OH）D level is between 20 and 30 ng/mL.