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Hypothalamus Differences in the Male and Female - Anatomy & Physiology (view source)
Revision as of 13:38, 4 September 2008
, 13:38, 4 September 2008no edit summary
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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