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== Endocrine Control of Follicular Growth and Steroidogenesis ==
 
== Endocrine Control of Follicular Growth and Steroidogenesis ==
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* Under gonadotrophin stimulation, the Antral follicle starts to grow.
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* Initially, FSH acts on granulosa cells to induce synthesis of oestrogens.
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* Oestrogen has a paracrine action within the ovary to induce the proliferation of granulosa cells.
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* During early-mid follicular phase of the oestrous cycle, plasma oestrogen exerts a negative feedback inhibition on gonadotrophin secretion.
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* As a result of this, FSH levels begin to fall.
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* The inhibiting effect of oestrogen only occurs whilst plasma oestrogen is below a certain threshold value.
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* During later stages of the follicular phase of the oestrous cycle, one follicle willl become dominant and it becomes the major producer of oestrogen.
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* Under the influence of oestrogen, granulosa cells which were previously unresponsive to LH, acquire LH-receptors and become responsive to LH.
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* The plasma concentration of oestrogen starts to rise.
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* When plasma concentrations rise above the threshold value, it acts to enhance gonadotrophin secretion by positive feedback.
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* The high level of oestrogen causes the LH surge that leads to ovulation.
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