Pituitary gland

 

The pituitary gland is an endocrine gland about the size of a pea. It is not a part of the brain, but  is a protrusion off the bottom of the hypothalamus.

The sella turcica (literally Turkish Saddle) is a saddle-shaped depression in the sphenoid bone of the human skull .  The seat of the saddle is known as the hypophyseal fossa, which holds the pituitary gland. The hypophyseal fossa is located in a depression in the body of the sphenoid bone. Located anteriorly to the hypophyseal fossa is the tuberculum sellae.

Thus we can see that it is surrounded by bone and that bone stretches to the forehead and the lower part of the face.

The pituitary is covered by a dural fold, - part of the dura mater, which is a sac that surrounds the spine and the brain – see spinal cord and cerebrospinal fluid.

 

The pituitary is functionally connected to the hypothalamus by a small tube called the Pituitary stalk.

The anterior pituitary gland secretes the following important endocrine hormones:

• HGH - 'Human Growth Hormone', released under the influence of hypothalamic Growth Hormone-Releasing Hormone (GHRH); inhibited by hypothalamic Somatostatin

• TSH - Thyroid-stimulating hormone , released under the influence of hypothalamic Thyrotropin-Releasing Hormone (TRH)

• ACTH - Adrenocorticotropic hormone, released under the influence of hypothalamic Corticotropin-Releasing Hormone (CRH)

• Beta-endorphin   - released under influence of hypothalamic Corticotropin-Releasing Hormone (CRH)

• PRL - Prolactin , also known as 'Luteotropic' hormone (LTH), whose release is inconsistently stimulated by
  • hypothalamic TRH
  • oxytocin
  • vasopressin
  • vasoactive intestinal peptide
  • angiotensin II
  • neuropeptide Y
  • galanin
  • substance P
  • bombesin-like peptides (gastrin-releasing peptide, neuromedin B and C)
  • neurotensin,
  and inhibited by hypothalamic dopamine.

• FSH and LH  - Luteinizing hormone and Follicle-stimulating hormone, both released under influence of Gonadotropin-Releasing Hormone (GnRH)

• MSH - Melanocyte–stimulating hormones or "intermedins," released by the pars intermedia, "the middle part"; adjacent to the posterior pituitary lobe

The posterior pituitary stores and secretes the following important endocrine hormones:

• Oxytocin  -  most of which is released from the paraventricular nucleus in the hypothalamus

• Antidiuretic hormone - ADH, also known as vasopressin

 

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 labour.

Hormones secreted from the pituitary gland help control the following body processes:

• Growth (Excess of HGH can lead to gigantism and acromegaly)
• Blood pressure
• Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth
• Breast milk production
• Sex organ functions in both males and females
• Thyroid gland function
• The conversion of food into energy (metabolism)
• Water and osmolarity regulation in the body
• Water balance via the control of reabsorption of water  by the kidneys
• Temperature regulation
• Pain relief

Observations

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• Dr Nadine Burke Harris - How childhood trauma affects health across a lifetime
• Heard, Gerald - Pain, Sex and Time - On sexual stimulation