HYPOTHALAMIC–PITUITARY–ADRENAL AXIS

By: Saddam Ansari

Tbilisi State Medical University

Introduction• HPA is also known as the limbic-hypothalamic-

pituitary-adrenal axis (LHPA axis) and hypothalamic-pituitary-adrenal-gonadotropic axis

• Complex set of direct influences and feedback interactions among the hypothalamus, the pituitary gland and the adrenal glands

Continued…

A major part of the neuroendocrine system that controls reactions to stress and regulates many body processes, including

• Digestion• Immune system• Mood and emotions• Sexuality• Energy storage and expenditure

Anatomy of HPA axis• The paraventricular nucleus of the hypothalamus

• secrete vasopressin and Corticotropin-releasing hormone (CRH)

• Anterior pituitary is activated and ACTH is released.

Continued…• The adrenal cortices, which produce glucocorticoid

hormones in response to stimulation by ACTH.

• CRH and ACTH production suppressed (negative feedback cycle)

Functions of HPA axis• Reduces proopiomelanocortin (POMC) cleavage into

ACTH and β-endorphins due to reduction in CRH and vasopressin.

• But epinephrine and norepinephrine secreted by adrenal medulla will positively feedback to the pituitary and increase the breakdown of POMCs into ACTH and β-endorphins.

Continued…• Sensory information arriving at the lateral aspect of the

amygdala is processed and conveyed to the central nucleus, which projects to several parts of the brain involved in responses to fear.

Continued…

Involved in the neurobiology of mood disorders and functional illnesses including

• Anxiety disorder

• Bipolar disorder

• Insomnia

• Post-traumatic stress disorder

• Borderline personality disorder

Continued…• ADHD

• Major depressive disorder

• Burnout

• Chronic fatigue syndrome

• Fibromyalgia

• Irritable bowel syndrome

• Alcoholism.

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