Changes

== Introduction ==

== Introduction ==

* The [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamus]] is inherently female.

* The [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] is inherently female.

* [[Testes Endocrine Function_-_Anatomy_%26_Physiology|Testosterone]] 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males.

* [[Testes Endocrine Function_- Anatomy & Physiology|Testosterone]] 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males.

* The female foetus has no testes to produce [[Testes Endocrine Function_-_Anatomy_%26_Physiology|testosterone]], thus developes a [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamic]] GnRH surge centre.

* The female foetus has no testes to produce [[Testes Endocrine Function_- Anatomy & Physiology|testosterone]], thus developes a [[Hypothalamus_- Anatomy & Physiology|hypothalamic]] GnRH surge centre.

== Defeminizing the Hypothalamus in the Male ==

== Defeminizing the Hypothalamus in the Male ==

* Testosterone crosses the [[Blood Brain Barrier - Anatomy & Physiology|blood-brain barrier]] and is converted into oestradiol.

* Testosterone crosses the [[Blood Brain Barrier - Anatomy & Physiology|blood-brain barrier]] and is converted into oestradiol.

* In the brain, oestradiol 'defeminizes' the [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamus]].

* In the brain, oestradiol 'defeminizes' the [[Hypothalamus_- Anatomy & Physiology|hypothalamus]].

* Surge centre function is minimized.

* Surge centre function is minimized.

* Complete 'defeminization' of the brain requires postnatal exposure to androgens.

* Complete 'defeminization' of the brain requires postnatal exposure to androgens.

* As a result, LH does not surge, it maintains a relatively consistent episodic pattern of secretion every day.

* As a result, LH does not surge, it maintains a relatively consistent episodic pattern of secretion every day.

** Episodes occur every 2-6 hours in the postpubertal male.

** Episodes occur every 2-6 hours in the postpubertal male.

* Steady, pulsatile GnRH and LH release results in a steady, pulsatile release of [[Testes Endocrine Function_-_Anatomy_%26_Physiology|testosterone]].

* Steady, pulsatile GnRH and LH release results in a steady, pulsatile release of [[Testes Endocrine Function_- Anatomy & Physiology|testosterone]].

== The Female Hypothalamus ==

== The Female Hypothalamus ==

* Foetal ovaries produce oestradiol, but this does NOT defeminize the [[Hypothalamus_-_Anatomy_%26_Physiology|Hypothalamus]].

* Foetal ovaries produce oestradiol, but this does NOT defeminize the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]].

* A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the [[Blood Brain Barrier - Anatomy & Physiology|blood brain barrier]], therefore oestradiol cannot effect the [[Hypothalamus_-_Anatomy_%26_Physiology|Hypothalamus]].

* A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the [[Blood Brain Barrier - Anatomy & Physiology|blood brain barrier]], therefore oestradiol cannot effect the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]].

* Alpha-fetoprotein is synthesized firstly by the embryonic yolk sac and then by the foetal liver.

* Alpha-fetoprotein is synthesized firstly by the embryonic yolk sac and then by the foetal liver.

* Alpha fetoprotein functions as:

* Alpha fetoprotein functions as:

** Carrier of fatty acids

** Carrier of fatty acids

* As GnRH surges, LH and Oestradiol surge about every 20 days in the female.

* As GnRH surges, LH and Oestradiol surge about every 20 days in the female.

** Surge frequency varies between species, dependent on the length of their [[Female_Reproductive_Tract_-Oestrous_Cycle_-_Anatomy_%26_Physiology|oestrous cycles]].

** Surge frequency varies between species, dependent on the length of their [[Female_Reproductive_Tract_-Oestrous_Cycle_- Anatomy & Physiology|oestrous cycles]].

* Between surges, there are low amplitude LH pulses.

* Between surges, there are low amplitude LH pulses.

[[Category:Reproductive System]]

[[Category:Reproductive System]]