激素,旧译荷尔蒙,是由内分泌腺或分散的内分泌细胞释放出来的“化学信使”。它们的分泌量极少,每毫升血中的含量一般在毫微克、微微克(1克的十亿分之一)的水平,可谓微乎其微,只有用最灵敏的放射免疫测定法才能够检测到。然而,它们的效力却极其强盛,作用至关重要,缺乏或释放过多都会产生疾病甚至引起死亡。人体的激素不下五十种之多,它们的作用又是严格分工的。各种激素均有其特定的所影响的器官或组织细胞,就好比射箭要对准靶子一样,被它们作用者,称 Hormones, old hormones, are chemical messengers released by endocrine glands or dispersed endocrine cells. They are minimally excreted, and the amount of blood per milliliter of blood is usually very small at nanograms and pico grams (1 gram per billion), which is negligible and detectable only with the most sensitive radioimmunoassays. However, their effectiveness is extremely strong, their role is crucial, and their lack of or over-release can lead to disease and even death. No less than 50 kinds of hormones in the human body, their role is strictly division of labor. Various hormones have their specific affected organs or tissue cells, like archery to target the same, by their role, said