Mr. G's online file also has the results of his recent blood tests. The only thing that looks abnormal is something called ANP - atrial natriuretic peptide. It is elevated. Why would this hormone be elevated in Mr. G, and what is it doing to him?

The atrial natriuretic peptide (ANP), atrial natriuretic factor (ANF), atrial natriuretic hormone (ANH), or atriopeptin is a polypeptide. It is closely related to homeostatic control of body water, sodium, potassium and adipose tissue. It is released by the muscle cells of the cardiac atrium (atrial myocytes), in response to increased blood pressure. The ANP acts in order to reduce the water, sodium and fat of adipose tissue in the circulatory system thus reducing blood pressure.