What is the role of a second messenger in the mechanism of protein hormone action?

(N/A) Protein hormones cannot enter the target cell because they are not lipid-soluble. Instead,they act by binding to specific receptors located on the outer surface of the plasma membrane,forming a hormone-receptor complex.
This complex stimulates the enzyme adenylate cyclase located on the inner surface of the plasma membrane. The activated adenylate cyclase enzyme converts $ATP$ into cyclic $AMP$ $(cAMP)$.
$cAMP$ acts as a second messenger,which carries the hormonal signal into the target cell. It then induces a specific enzyme system through a cascade effect,leading to the desired physiological or biochemical response within the cell.