Target cells are the receptors of the hormone. Hormones have a specific target cell. It responds to the hormone because it has receptors for the hormone. Hormone receptors are found either the surface or inside of the cell.
Binding of hormone to the receptor initiates the reaction. The TRH target cell is located in the cytoplasm intra-cellularly. In order to bind to the specific receptor the hormone has to travel to the membrane of the cell and bind to the DNA.
