Grey's Anatomy, Season 12

Meredith:
[opening voice-over] The body has approximately eleven organ systems, all doing different things at the same time. In order to keep us functioning, or, well, alive, they need one voice, a leader, a master. And in our brains, that job belongs to the pituitary gland. It senses the body's needs before they even arise, working non-stop. The pituitary gland communicates with all of the other glands, telling them when to produce the vital hormones we need to function. It keeps everything running smoothly, in perfect order. There's no denying it. It has the toughest job in the place.