1. Adrenocorticotropin (ACTH)-induced steroidogenesis, obtained by continuous administration of ACTH for 3 days, produces in man (a) sustained elevations of plasma deoxycorticosterone and cortisol concentrations, (b) transient elevations of plasma aldosterone and 18-hydroxycorticosterone concentrations that return to near-control values, and (c) brisk initial increases in plasma 18-hydroxydeoxycorticosterone and corticosterone concentrations that fall to 20–68% of peak values 30 h thereafter.
2. Dexamethasone (8 mg/day, orally) treatment for 2 days in man permits a greater postural increase in plasma aldosterone and 18-hydroxycorticosterone concentrations. A dampening effect of ACTH is suggested.
3. An ACTH-initiated inhibition of 11β- and 18-hydroxylation is proposed to be operative in regulation of mineralocorticoid hormones.