Pituitary gland

endocrine gland at the base of the brain

The pituitary gland (or hypophysis) is an important part of the endocrine system. It is at the base of the brain between the eyes. The pituitary is attached to the hypothalamus, which is also a gland. The pituitary controls a whole range of vital functions by secreting hormones.

Position of pituitary and hypothalamus
Position of the pituitary (detail)

The pituitary gland consists of two parts: the anterior pituitary and the posterior pituitary. It is functionally linked to the hypothalamus by the pituitary stalk (also called the infundibulum).[1]

The hypothalamus releases factors down the pituitary stalk to the pituitary gland where they cause the release of pituitary hormones. Although the pituitary gland is known as the 'master' endocrine gland, both of the lobes are under the control of the hypothalamus.[2] Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by neurosecretory cells in the hypothalamus.

Hormones released change

The gland releases several kinds of hormones.

Anterior pituitary change

The endocrine cells of the anterior pituitary are controlled by neurosecretion from the hypothalamus. The anterior pituitary cells synthesizes and secretes these important endocrine hormones:

The two gonadotropins;

Intermediate lobe

Here one hormone is produced:

Posterior pituitary change

The posterior pituitary is actually an extension of the hypothalamus. Neurosecretory cells in the hypothalamus have axons that go right down into the posterior pituitary.[3] The posterior pituitary stores and secretes the hormones produced by these neurosecretory cells:

  • Oxytocin, most of which is released from the hypothalamus: has effects on nerve transmission, and on females during and after birth. Has a role in pair-bonding, mating and maternal behaviour. Functions not yet entirely understood.
  • Antidiuretic hormone (ADH, also known as vasopressin): controls the reabsorption of molecules in the tubules of the kidneys. Increases arterial blood pressure. It plays a key role in homeostasis, and the regulation of water, glucose, and salts in the blood.

Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which, in turn, increases uterine contractions. This positive feedback loop continues throughout birth labour.

References change

  1. "Median eminence - Glossary of Biochemistry and Molecular Biology". Archived from the original on 2011-07-11. Retrieved 2011-06-27.
  2. Dasen, J. S.; Rosenfeld, M. G. (1 December 1999). "Signaling mechanisms in pituitary morphogenesis and cell fate determination". Current Opinion in Cell Biology. 11 (6): 669–677. doi:10.1016/s0955-0674(99)00034-4. PMID 10600709 – via PubMed.
  3. Boron, Walter F. & Boulpaep, Emile L. 2009. Medical physiology. 2nd ed, Philadelphia: Saunders Elsevier. pp. 1016–1017. ISBN 978-1-4160-3115-4

Endocrine system
Adrenal gland - Corpus luteum - Hypothalamus - Ovaries - Pancreas - Parathyroid gland - Pineal gland - Pituitary gland - Testes - Thyroid gland - Hormone