(N/A) $FSH$ (Follicle Stimulating Hormone),being a glycoprotein,is insoluble in lipids and therefore cannot enter the target cells.
It binds to specific receptor molecules located on the surface of the cell membrane to form a hormone-receptor complex.
This complex triggers the release of the enzyme adenylate cyclase from the receptor site.
This enzyme catalyzes the conversion of $ATP$ into cyclic adenosine monophosphate $(cAMP)$ within the cell.
The $cAMP$ then activates the existing enzyme system of the cell,which accelerates metabolic reactions.
The hormone is referred to as the first messenger,while $cAMP$ is termed the second messenger.
Additionally,the hormone-receptor complex alters the permeability of the cell membrane to facilitate the transport of materials,thereby increasing cellular activity.