Abstract: 11β-hydroxysteroid dehydrogenase(11β-HSD) is the GC metabolic enzymes secreted by the human placenta.It works on glucoeorticoids(GC) which has a great regulating effect between placenta and fetal membranes.Meanwhile,11β-HSD is keeping the fetus away from large amout of GC that may result in fetal physical deterioration or diabetes.As known,11β-HSD has two subtypes,11β-HSD1 and 11β-HSD2.11β-HSD1 is a kind of oxidordeuctase with low affinity and it mainly performs its reductase activity.11β-HSD1 mainly activates the inert cortisone,E to become viable cortisol,F.So regeneration and efficiency of GC is activated; 11β-HSD2 is a kind of dependency dehydrogenase with high affinity and it mainly performs a single oxidase.The main function is transforming catalytic cortisol from its active state into the inactive state,which blocks the matrix concentration above the level of the fetal 5 ~ 10 times of GC into the placenta,then forms the GC barrier protection of the normal growth and development of fetus.

Key words: 11β-hydroxysteroid dehydrogenase, Human placenta, Glucoeorticoids, Protective effect