Hypothalamus

The hypothalamus is a portion of the brain near the third ventricle, located below the thalamus and above the brainstem. The anterior boundary of the hypothalamus is determined by the line connecting the anterior commissure, the lamina terminalis and the optic chiasm. The lower limit of the hypothalamus is formed by the infundibulum, the tuber cinerum and the mamillary bodies. The posterior limit is represented by a straight line joining the mamillary bodies and the posterior commissure.

The hypothalamus is involved in the following control systems:
• body temperature
• autonomic nervous system
• emotional and food behavior
• endocrine (via the pituitary)
• circadian rhythm.

What Is the Hypothalamus?

The hypothalamus is found in the region below the thalamus, a structure that makes up most of the lateral walls of the brain’s third ventricle(1).

The hypothalamus is a small cone-shaped structure that is an integral part of the brain, functioning as a control center of the autonomic nervous system(2).

Bodily functions, such as digestion, pupillary response, heart rate, respiratory rate, sexual arousal, and urination, are regulated by the autonomic nervous system(3).

One of the hypothalamus’ crucial functions is maintaining the body’s stability (homeostasis)(4). This part of the brain responds to a wide range of internal and external signals, such as hunger, blood pressure, body temperature, and hormone levels(5).

Due to the hypothalamus and pituitary gland’s relationship, the hypothalamus also affects the endocrine system(6).  The pituitary gland and the hypothalamus operate together in the hypothalamic-pituitary axis(7).

There are two nerve cells in the hypothalamus that produce two different types of hormones(8).

One of the nerve cells produces the anti-diuretic hormone, which induces water reabsorption in the kidneys, and oxytocin, which is significant during childbirth and breastfeeding(9). These hormones are sent down through the pituitary stalk and to the posterior lobe of the pituitary gland(10).

Meanwhile, the other nerve cell releases inhibiting and stimulating hormones that are carried by blood vessels in the anterior lobe of the pituitary gland to the pituitary stalk(11). These hormones modulate the adrenal cortex (the most extensive of the adrenal gland found in its outer regions), gonads, and the thyroid gland(12).

The hypothalamus can be found above the pituitary gland and below the third ventricle in the ventral area of the brain(13). Divided into four regions, it is mainly made up of nuclei (compact cluster of neurons) that release hormones(14).

Preoptic Region

This region contains the preoptic nucleus(15). This preoptic nucleus is responsible for regulating the secretion of gonadotropin (stimulates the gonads and sex glands) that is essential for sexual reproduction(16).

Supraoptic Region

The supraoptic region consists of the anterior nucleus (for episodic memory), supraoptic nucleus (produces anti-diuretic hormone and oxytocin), and the suprachiasmatic nucleus (controls circadian rhythms)(17).

This region helps in parturition (giving birth) through the excretion of oxytocin and the regulation of osmolality (the measure of the concentration of the particles from the anti-diuretic hormone production)(18).

Tuberal Region

This region is responsible for the modulation of feeding impulses(19). The tuberal area contains the ventromedial nucleus (involved in fear, thermoregulation, sexual activity, and hunger) and dorsomedial nucleus (involved in circadian activity and body weight regulation)(20).

Mammillary Region

The region that houses the posterior nucleus and mammillary nucleus is the mamillary region. The posterior nucleus is responsible for the thermoregulation of the body(21). It operates by heat conservation and can result in hypothermia (body losing heat quickly) when damaged(22).

Meanwhile, the mammillary nucleus is responsible for episodic and spatial memory collection in the brain(23). This nucleus also aids in certain behaviors related to goal-orientedness, rewards, and emotions(24).  Damage to this region may cause amnesia(25).

Clinical Significance of the Hypothalamus

Each of the nuclei in the hypothalamus exerts a crucial influence on bodily functions. Any impairment or injury to these nuclei may affect the operation of the hypothalamus(26).

For instance, the damage of the suprachiasmatic nucleus may result in circadian rhythm dysfunction. Meanwhile, the impairment of the lateral nucleus may result in a decrease in appetite(27).

Some of the impairments in the hypothalamus nuclei may be caused by ischemia (blood supply restriction), intracranial masses (tumor), or by certain antipsychotics and medications(28).

Aside from these deficiencies, disorders in the hypothalamus regions may result in more severe diseases or clinical syndromes(29).

Central Hypothyroidism

This condition is due to pituitary and hypothalamic disorders(30). It involves the growth of infiltrative lesions (spread out of inflammatory diseases), mass lesions (cancer cells), and infections, such as traumatic brain injury, radiation, stroke, and tuberculosis(31).

Hypothyroidism’s common symptoms include a lack of energy (lethargy), hair loss, dry skin, sensitivity to cold, weight gain, sexual dysfunction, and constipation(32).

Acromegaly and Pituitary Gigantism

These disorders are associated with growth(33). Pituitary gigantism happens because of the oversecretion of the growth hormone in the pituitary gland(34).

The excessive secretion of the growth hormone may result in the oversecretion of insulin-like growth in the liver. It may modulate growth in the skeletal muscles, bones, cartilages, liver, lung cells, and nerves. This excessive secretion may also regulate cellular DNA synthesis(35).


  1. Utiger, R. D., (n.d.), Hypothalamus, retrieved from https://www.britannica.com/science/hypothalamus
  2. Ibid.
  3. Libre Text Medicine, (August 2020), Autonomic Reflexes, retrieved from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/14%3A_Autonomic_Nervous_System/14.2%3A_Structure_of_the_Autonomic_Nervous_System/14.2F%3A_Autonomic_Reflexes
  4. You and Your Hormones, (n.d.), Hypothalamus, retrieved from https://www.yourhormones.info/glands/hypothalamus/
  5. Ibid.
  6. Utiger, R. D., Op. Cit.
  7. Shahid Z, Asuka E, Singh G. Physiology, Hypothalamus. [Updated 2020 May 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535380/
  8. You and Your Hormones, (n.d.), Hypothalamus, retrieved from https://www.yourhormones.info/glands/hypothalamus/
  9. Ibid.
  10. Ibid.
  11. Ibid.
  12. Ibid.
  13. Shahid Z, Asuka E, Singh G. Physiology, Hypothalamus. [Updated 2020 May 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535380/
  14. Crumbie, L., (November 2020), Hypothalamus, retrieved from https://www.kenhub.com/en/library/anatomy/hypothalamus
  15. Ibid.
  16. Ibid.
  17. Crumbie, L., Op. Cit.
  18. Ibid.
  19. Ibid.
  20. Ibid.
  21. Ibid.
  22. Ibid.
  23. Peterson DC, Reddy V, Mayes DA. Neuroanatomy, Mammillary Bodies. [Updated 2020 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537192/
  24. Ibid.
  25. Ibid.
  26. Shahid Z, Op. CIt.
  27. Ibid.
  28. Ibid.
  29. Ibid.
  30. Ibid,
  31. Ibid.
  32. Ibid.
  33. Ibid.
  34. Ibid.
  35. Ibid.

References

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