Hormones provide a form of communication between different cells and from one organ to another. The dramatic effects of hormones on physiologic functions such as growth and metabolism have allowed relatively sophisticated studies to elucidate their sources of production, sites of action, and how they are controlled. Because hormones act by binding to specific receptors, studies that have defined
... [Show full abstract] their mechanisms of action have also provided important paradigms for how receptors activate intracellular signaling cascades that lead to altered cellular responses.