What hormone promotes a decrease in blood pressure and a loss of sodium and water in urine?

Atrial natriuretic peptide (ANP) is the hormone that decreases blood pressure by promoting the excretion of sodium through the urine, which leads to a reduction in blood volume. When the atria of the heart are stretched due to increased blood volume, such as in cases of heart failure or high blood pressure, they release ANP. This hormone works primarily by inhibiting the renin-angiotensin-aldosterone system (RAAS), which is responsible for retaining sodium and water, thus leading to vasodilation and lowering blood pressure.

Additionally, ANP increases glomerular filtration rate, further enhancing sodium and water loss. The overall effect of ANP is to alleviate the burden on the heart by reducing the volume of fluid that must be pumped, thus decreasing the pressure within the cardiovascular system.

The other hormones listed do not have this specific effect on blood pressure: insulin primarily regulates glucose metabolism, adrenaline prepares the body for 'fight or flight' responses increasing heart rate and blood pressure, and cortisol is involved in stress responses and maintains blood sugar levels, among other functions.