Difference between revisions of "Hypothalamus Differences in the Male and Female - Anatomy & Physiology"

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== Introduction ==
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* The hypothalamus is inherently female.
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* Testosterone 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males.
 +
* The female foetus has no testes to produce testosterone, thus developes a hypothalamic GnRH surge centre.
 +
 +
== Defeminizing the Hypothalamus in the Male ==
 +
 +
* Testosterone crosses the blood-brain barrier and is converted into oestradiol.
 +
* In the brain, oestradiol 'defeminizes' the hypothalamus.
 +
* Surge centre function is minimized.
 +
* Complete 'defeminization' of the brain requires postnatal exposure to androgens.
 +
* Continued exposure to androgens is required to render the surge centre inoperative.
 +
 +
 +
== The Female Hypothalamus ==
 +
 +
* Foetal ovaries produce oestradiol, but this does NOT defeminize the hypothalamus.
 +
* A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the blood brain barrier, therefore oestradiol cannot effect the hypothalamus.
 +
* Alpha-fetoprotein is synthesized firstly by the embryonic yolk sac and then by the foetal liver.
 +
* Alpha fetoprotein functions as:
 +
** Foetal blood osmotic regulator
 +
** Carrier of fatty acids

Revision as of 13:38, 4 September 2008

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Introduction

  • The hypothalamus is inherently female.
  • Testosterone 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males.
  • The female foetus has no testes to produce testosterone, thus developes a hypothalamic GnRH surge centre.

Defeminizing the Hypothalamus in the Male

  • Testosterone crosses the blood-brain barrier and is converted into oestradiol.
  • In the brain, oestradiol 'defeminizes' the hypothalamus.
  • Surge centre function is minimized.
  • Complete 'defeminization' of the brain requires postnatal exposure to androgens.
  • Continued exposure to androgens is required to render the surge centre inoperative.


The Female Hypothalamus

  • Foetal ovaries produce oestradiol, but this does NOT defeminize the hypothalamus.
  • A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the blood brain barrier, therefore oestradiol cannot effect the hypothalamus.
  • Alpha-fetoprotein is synthesized firstly by the embryonic yolk sac and then by the foetal liver.
  • Alpha fetoprotein functions as:
    • Foetal blood osmotic regulator
    • Carrier of fatty acids
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