Ball-and-stick model of the cortisol (hydrocortisone) molecule (C21H30O5).

Cortisol is a hormone that all humans produce in their adrenal cortex (on the edge of the adrenal glands). Although all the physiological elements of cortisol have not been determined, this hormone is known as a regulator of energy. It performs this duty by directing the body to utilize the correct fuel for the particular situation. Cortisol also directs the maturation of certain fat cells and is a immune suppressant during stressful situations.

Photo Credit: 
Ben Mills on Wikimedia Commons