FSH is a pituitary hormone, which falls under the category of peptide/protein hormones . Hormones that interact with membrane-bound receptors (like FSH) normally do not enter the target cell; therefore, Assertion (A) is True . Binding of such hormones to their receptors generates second messengers (e.g., cyclic AMP, IP3, Ca++) which regulate cellular metabolism; therefore, Reason (R) is True . However, the generation of the second messenger is the mechanism of action that follows binding, not the cause of the hormone's inability to enter the cell. The inability to enter is due to the lipid-insoluble nature of protein hormones. Thus, (R) is not the correct explanation of (A).