The water-soluble hormone cannot pass through the lipid bilayer of the plasma membrane and enter the cell, so it uses plasma membrane receptors to activate second messengers such as cyclic AMP (CAMP). Knowing this, please complete this exercise.

1. A hormone such antidiuretic hormone (ADH) acts as the (primary? secondary/?) messenger as it carries a message from the (endocrine? exocrine?) where it is secreted to the outside of the target cell.