How Do Hormones Cause Ovulation?

To anwser this question, let’s take a quick look at what is normally going on inside the female body body each month.

The Starting Place:

• It all starts with the hypothalamus in the brain producing GnRH (gonadotropinreleasing hormone)
• The GnRH will then trigger the pituitary gland to release the follicle stimulating hormone (FSH)

The Follicle Stimulating Hormone:

• The FSH then makes the journey to the female's ovaries (via the bloodstream)
• Once it arrives, it initiates the growth of a follicle

The Role of the Follicle:

• When the follicle develops, it generates estrogen
• After about 10 days, the estrogen levels reach high numbers
• The estrogen levels peak approximately 1 day before ovulation (typically, this is day 13 in a standard 28 day cycle)
• This peak elicits a surge of luteinizing hormone (LH) from the pituitary gland.

The LH Surge:

• This surge acts a cue to the ovarian follicle
• About 36 hours later, a mature egg is released into the fallopian tube
• The egg leaves behind the corpus luteum (the empty follicle)

The Corpus Luteum:

• The cells of the corpus luteum then produce progesterone and estrogen
• Together, these two hormones stimulate the uterine lining to thicken with blood
• This is done to prepare the uterus walls for nurturing a fertilized egg

The Shrinking of the Corpus Luteum:

• The corpus luteum will begin to diminish
• This leaves the uterine lining with no hormonal support
• The lining will begin to shed off
• The female's monthly period begins
  
  

  The low levels of estrogen and progesterone also signal the hypothalamus to start the process over again.

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