无效率的

Itamin D from the skin and diet is metabolized in the lier to 25-hydroxyitamin D (Figure 1), which is used to determine a patient's itamin D status1,2,3,4; 25-hydroxyitamin D is metabolized in the kidneys by the enzyme 25-hydroxyitamin D-1-hydroxylase (CYP27B1) to its actie form, 1,25-dihydroxyitamin D.1,2,3,4 The renal production of 1,25-dihydroxyitamin D is tightly regulated by plasma parathyroid hormone leels and serum calcium and phosphorus leels.1,2,3,4 Fibroblast growth factor 23, secreted from the bone, causes the sodium–phosphate cotransporter to be internalized by the cells of the kidney and small intestine and also suppresses 1,25-dihydroxyitamin D synthesis.5 The efficiency of the absorption of renal calcium and of intestinal calcium and phosphorus is increased in the presence of 1,25-dihydroxyitamin D (Figure 1).2,3,6 It also induces the expression of the enzyme 25-hydroxyitamin D-24-hydroxylase (CYP24), which catabolizes both 25-hydroxyitamin D and 1,25-dihydroxyitamin D into biologically inactie, water-soluble calcitroic acid.2,3,4

从皮肤和食物来的维生素D在肝中代谢为25-羟基维生素D（图1），被用来决定病人体内维生素D情况的1，2，3，4；25-羟基维生素D在肾中被25-羟基维生素D1羟化酶（CYP27B1）转变为有活性的1，25-二羟基维生素D 。1，2，3，4由肾产生1，25-二羟基维生素D是被血浆甲状旁腺激素和血清钙，磷水平紧密调节。1，2，3，4由骨分泌的成纤维细胞生长因子23使钠磷协同转运蛋白被肾和小肠细胞内化及抑制1，25-二羟维生素D合成。5 在1，25-二羟基维生素D作用下肾和小肠吸收钙及磷的效率增高(图1)。2，3，6 它也包括25-羟四- 24 -羟化酶的表达(CYP24)，且将1，25二羟基维生素D和25羟基维生素D异化成无生物活性，水溶性的维生素D3-23羧酸。2，3，4

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。