Now, the first thing that we should know about all these six hormones that are released by the interior pituitary gland is they're all peptide hormones. That means they're formed in the rough endoplasmic reticulum of our endocrine cells. They are modified in the Golgi apparatus and they are released into our blood system. Now, once they're inside the blood, they are water soluble and that means they do not need a carrier protein. And once they locate the target cells, these six proteins, these six hormones all bind to receptor proteins found on the plasma membrane of the target cells. So, because they can't actually pass across the cell membrane of the target cell, they have to bind to the surface of the plasma membrane of the target cells.