Answer to Question #68112 in Human Anatomy and Physiology for francesca

Question

The adrenocorticotrophic hormone travels to the adrenal cortex where it triggers the secretion of the glucocorticoids. How it triggers?

Answer 1

The adrenocorticotrophic hormone (ACTH) binds to the adrenocorticotrophic hormone receptors on the surface of adrenocortical cells, primarily located in the adrenal cortex. Then it triggers the secretion by rapid short-term and slower long-term actions. ACTH rapidly stimulates cholesterol delivery to the mitochondria where the P450scc enzyme is located. This enzyme acts as a catalyst in the first step of steroidogenesis that is cleavage of the side-chain of cholesterol. The slower action is that ACTH stimulates the transcription of the genes for steroidogenic enzymes, especially the P450scc enzyme mentioned above, the steroid 11β-hydroxylase, and their associated electron transfer proteins. Another action is that ACTH also stimulates lipoprotein uptake into cortical cells; thus increasing the bioavailability of cholesterol in the cells of the adrenal cortex which is needed for the synthesis of glucocorticoids.