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 液吸收，并转化为活性形式（一种开环甾体激）和储存形式（25-羟基生 D）——其功能更像是一种激而不是生。

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.

这些要么是基于氨基酸的水溶性，要么是甾体和脂溶性，可能针对多种类型的细胞，或者只是针对特定的细胞。