I still have my gallbladder. The HPA axis is the hypothalamic–pituitary–adrenal axis. It can get a little complicated so you might just want to google it for a better understanding but basically the organs that make that up the HPA axis (hypothalamu, pituitary gland and adrenal glands) interact and provide feedback which regulate a lot of body processes such as immunity, mood, energy, emotions and most importantly stress response. For example, when someone gets stressed the hypothalmus produces corticotropin-releasing hormone (CRH) which then signals the pituitary gland to produce adrenocorticotropic hormone (ACTH) which then signals the adrenal glands to produce cortisol. Alcohol can trigger the HPA axis and over time, disrupt it which can cause higher cortisol levels. Most of the research out there is based on continuous consumption of alcohol over an extended period of time so you shouldn't t see high cortisol numbers (like Cushing's high) in someone drinking responsibly and abstaining from drinking during testing.