HPA AdaptHPA Adapt Supporting Stress Hormone Balance via the HPA Axis with Adaptogenic Herbs* The hypothalamic pituitary adrenal axis, or HPA axis, is the central part of the stress response system. It involves a complex set of interactions and feedback loops between the hypothalamus, the pituitary, and the adrenal glands. The HPA axis also plays a role in the regulation of other systems of the body, including the gastrointestinal, neurological, and immune