Treatment of adult male rats with estradiol-17β for 7 days results in adrenal hyperplasia, increased level of serum ACTH along with reduction in serum level of α2u-globulin and inhibition of adrenal 5-ene-3β-hydroxysteroid dehydrogenase (5-ene-3β-HSD) activity. Administration of corticosterone in estrogen-treated rats reverses the effects of estrogen while in normal rats corticosterone treatment reduces adrenal weight, serum ACTH and adrenal 5-ene-3β-HSD activity. In vitro experiments show that α2u-globulin fails to change adrenal 5-ene-3β-HSD activity in corticosterone pretreated rats while in normal and estrogen pretreated rats α2u-globulin increases 5-ene-3β-HSD activity. © 1983.