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Structure

Hypothalamus

Not medically reviewed · Content last updated · 1 min read ·

This is the date the draft was written, not a medical review date.

The hypothalamus is a small diencephalic region that integrates autonomic, endocrine and behavioural responses to maintain homeostasis. It controls the pituitary gland through neurosecretory and portal pathways.

Terminologia Anatomica (Latin): Hypothalamus · Open in the 3D atlas

Location

Below the thalamus, forming the floor and lower walls of the third ventricle; it extends from the optic chiasm to the mammillary bodies and is continuous with the infundibulum and pituitary stalk.

Structure

Organised in zones and regions with named nuclei: supraoptic and paraventricular (vasopressin, oxytocin), arcuate (releasing and inhibiting factors), suprachiasmatic (circadian rhythm), preoptic and anterior (heat loss), posterior (heat conservation), ventromedial (satiety), lateral (hunger) and mammillary nuclei.

Blood supply

Branches of the circle of Willis: the anterior communicating, posterior communicating and proximal posterior cerebral arteries, together with the superior hypophyseal arteries that feed the primary portal capillary plexus.

Innervation

Connections: afferents from the limbic system, brainstem (including the nucleus of the solitary tract), retina and circulating signals; efferents through the medial forebrain bundle, mammillothalamic tract, descending autonomic pathways, the hypothalamo-hypophyseal tract and the tuberoinfundibular system.

Function

It regulates body temperature, water balance and thirst, feeding, sleep-wake and circadian rhythm, sympathetic and parasympathetic output, and reproductive and stress axes. Vasopressin and oxytocin are made in the supraoptic and paraventricular nuclei and released from the posterior pituitary; releasing hormones reach the anterior pituitary through the hypophyseal portal system.

Clinical correlations

Lesions (tumour, craniopharyngioma, trauma) may cause diabetes insipidus, disturbed temperature regulation, hyperphagia or hypophagia, sleep disorders and hypopituitarism. Mammillary body damage is a feature of Wernicke encephalopathy.

Common exam points

  • Floor of the third ventricle between the optic chiasm and the mammillary bodies.
  • Supraoptic and paraventricular nuclei make vasopressin and oxytocin (posterior pituitary).
  • Releasing hormones travel to the anterior pituitary via the hypophyseal portal system.
  • Suprachiasmatic nucleus: circadian pacemaker; preoptic region: heat loss; lateral area: hunger.
  • Lesions: diabetes insipidus, thermoregulation and appetite disorders.

References

  1. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
  2. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  3. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology. Elsevier, 14th edition (2020) — Tier 3 (textbook)

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