Vitamin D is absorbed into our bloodstream and converted to the active form (a secosteroidal hormone) and a storage form (25-hydroxyvitamin D) – it functions more like a hormone than a vitamin.

生 D 被血液吸收，并转化为活性形式（种开环甾体）储存形式（25-羟基生 D）——其功能更种而不生。

These hormones are either amino-acid based and water soluble, or steroidal and lipid-soluble, and may target many types of cells or just turn on specific ones.

这些荷尔蒙要么基于氨基酸的水溶性荷尔蒙，要么甾体脂溶性荷尔蒙，可能针对多种类型的细胞，或者只针对特定的细胞。