Answer:
Intracellular mediator or the secondary messenger molecules
Explanation:
The hormones act on the target cell or a group of target cells by binding to the hormone receptors present in the membrane of the target cells.
The hormones which are composed of the lipids bins to the intracellular receptors but the amino acid-based hormones are not able to diffuse into the cell and thus binds to the membrane-bound receptors.
This involves the signal transduction by the production of the secondary messenger molecules. The messenger molecules act as intracellular mediators like the cyclic AMP, cyclic GMP and the cyclic CMP.
Thus, the secondary messenger is the correct answer.
