Hypothalamic–pituitary–adrenal axis (HPA axis) (HPA axis)

The hypothalamic–pituitary–adrenal (HPA) axis is a major neuroendocrine system that regulates the body's response to stress and maintains homeostasis [1, 4]. It involves a cascade of hormonal signals: the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary to secrete adrenocorticotropic hormone (ACTH), which then prompts the adrenal cortex to produce glucocorticoids, primarily cortisol [4, 10]. This system is governed by a negative feedback loop where cortisol inhibits the further release of CRH and ACTH to prevent over-activation [6, 11]. Dysregulation of the HPA axis is implicated in numerous conditions, including Cushing's syndrome, Addison's disease, and psychiatric disorders like depression and PTSD [2, 9, 13]. Pharmacological agents interact with the axis by targeting specific components, such as glucocorticoid receptors (e.g., dexamethasone) or steroidogenic enzymes (e.g., metyrapone), to modulate hormonal output [1, 12]. Chronic activation or suppression of this axis can lead to significant metabolic, immune, and psychological consequences [10, 13]. The axis also plays a critical role in regulating digestion, immune function, mood, and energy expenditure [4, 9]. Therapeutic strategies often focus on restoring the balance of this feedback loop to treat stress-related and endocrine pathologies [3, 12].

Other names

Hypothalamic–pituitary–adrenocortical axisHTPA axisLimbic-hypothalamic-pituitary-adrenal axisLHPA axis

Modulation of the neuroendocrine feedback loop through glucocorticoid receptor agonism or antagonism, inhibition of steroidogenesis enzymes, or stimulation of hormone release via synthetic analogs of CRH or ACTH [1, 6, 12].