Fig. 7.4 
Simplified mechanism of anion of ACTH on the adrenocortical cell.
The ACTH receptor is linked to the adenylate cyclase membrane enzyme system which is responsible for cAMP production. This ‘second messenger’ triggers the intracellular events that are responsible for steroid production and secretion. Pregnenolone is subsequently converted to other corticosteroids (see Figs 7.6 and 7.12).