The pituitary gland is central to the regulation and functional integrity of many peripheral hormone systems. Based at the base of the brain, the pituitary integrates signals from the hypothalamus with feedback from the peripheral endocrine glands, and in turn, releases the requisite amount of hormone or trophic factor for the ambient metabolic and physiological conditions. The past decades have seen key milestones in recombinant production of all known pituitary and hypothalamic hormones, characterisation of their receptors and discovery of additional hypothalamic peptides regulating the pituitary. These have enabled an in‐depth understanding of hypothalamic–pituitary physiology and pathophysiology.

Key Concepts

  • The pituitary gland is centrally regulated by the hypothalamus.
  • The anterior pituitary (adenohypophysis) contains five distinct glandular cell types that secrete growth hormone (GH), prolactin, gonadotrophins (luteinizing hormone, LH; follicle‐stimulating hormone, FSH), adrenocorticotropic hormone (ACTH) and thyroid‐stimulating hormone (TSH).
  • Anterior pituitary hormones are secreted in pulses under control of hypothalamic trophic factors released in the hypophyseal portal circulation.
  • The ultradian pulsed patterns of GH, prolactin, ACTH and TSH secretion follow endogenous circadian rhythms.
  • Peripheral hormones released from target endocrine organs regulate secretion of anterior pituitary hormones in negative feedback loops, with the exception of prolactin.
  • Prolactin is produced by pituitary lactotrophs and is tonically inhibited by the hypothalamic neurotransmitter, dopamine.
  • The neurohypophysis (posterior pituitary) is constituted of axonal projections extending from the hypothalamic supraoptic and paraventricular nuclei that secrete arginine vasopressin (AVP) and oxytocin.
  • Posterior pituitary hormones are secreted and regulated via neural pathways to coordinate water balance and reproductive function.

Keywords: adenohypophysis; neurohypophysis; hypothalamus; trophic factors; pituitary hormone

Figure 1. Control of hypothalamic–pituitary–target organ axes. From Melmed S (2001) “Disorders of anterior pituitary and hypothalamus”. In: Braunwald E, Facui AS, Kasper DL et al. (eds). Harrison's Principles of Internal Medicine, 15th edn, p. 2030. New York: McGraw‐Hill.
Figure 2. Model for development of the human anterior pituitary gland and cell‐lineage determination by a cascade of transcription factors. Trophic cells are depicted with transcription factors known to determine cell‐specific gene expression. Adapted from Shimon I and Melmed S (1996). “Anterior pituitary hormones”. In: Conn P and Melmed S (eds). Scientific Basis of Endocrinology, pp. 40–47. Totowa, NJ: Humana Press.
Figure 3. Structural – functional humoral, endocrine and neuroendocrine relationships within the hypothalamic–pituitary unit.
Figure 4. Functional neuroanatomy of the kisspeptin system and its role in central regulation of gonadotrophin release. POA, preoptic area of hypothalamus; KNDy, kisspeptin neurokinin dynorphin neuron; GnRH, gonadotrophin‐releasing hormone; GNRH‐R, gonadotrophin‐releasing hormone receptor; LH, luteinizing hormone; FSH, follicle‐stimulating hormone; ERα, oestrogen receptor alpha; PR, progesterone receptor; NKB, neurokinin‐B; DyN, dynorphin. Green arrows represent stimulatory action, red arrows represent inhibitory action via negative feedback.


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Further Reading

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Melmed S, Koenig R, Rosen C, Auchus R and Goldine A (2015) Williams Textbook of Endocrinology, 13th edn. Elsevier: USA.

Melmed S (2017) The Pituitary, 4th edn . Chapters 1–8, pp 3–282. Academic Press: USA.

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Seejore, Khyatisha, and Murray, Robert D(Aug 2020) Pituitary. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0029139]