Reproductive Endocrinology 101

I'm doing this post in an effort to explain what is going on with the IVF stuff.  In order to explain IVF, a simple understanding of the female menstrual cycle is required.  The above picture is a perfect example of the phrase "a picture is worth a thousand words" as it graphically explains what happens during a normal menstrual cycle.

Basically, hormones from the brain (FSH & LH) stimulate multiple follicles in the ovary.  As the follicles grow, increasing amounts of estrogen cause tissue in the uterus to grow, preparing for implantation of an embryo and pregnancy.  Eventually one of the follicles is selected as the "dominant follicle," the other follicles die off, and a massive surge in LH causes the dominant follicle to ovulate.  At this time, the hormone levels drop off with the exception of progesterone.  Progesterone is produced by the unit that contained the follicle before it was ovulated.  Progesterone maintains the uterine lining in preparation of implantation and pregnancy.  If pregnancy occurs, the placenta develops and it takes over the role of producing progesterone.  If pregnancy does not occur, progesterone levels decrease and the uterine lining built by estrogen cannot be maintained.  The lining sheds resulting in a menstrual period and the cycle starts over for the next month.

For IVF, medicines like follistim and menopur are given to help encourage follicle growth.  After a short trial of these medicines, lab work and ultrasounds are done to assess follicle growth.  Once an appropriate number of follicles are produced, another medicine such as ganirelix is given to prevent the natural LH surge and ovulation.  This is to allow for continued growth of the follicles.  The goal is to grow as many follicles as possible without over stimulating the ovaries, which can be dangerous.  Once an appropriate number of follicles are present, a "trigger shot" is given to induce ovulation.  Shortly after the trigger shot, just prior to ovulation, the follicles are retrieved using a long needle.  The follicles are then taken to a lab where a sperm cell is injected into the egg.  The embryo is then implanted into the uterus resulting in pregnancy.

In order for the female ovulation and menstrual cycle to work correctly, it requires an amazing and  complex set of hormones and body systems communicating in perfect harmony.  I think it's absolutely amazing how this system works as well as it does.  It's also pretty cool how it can be manipulated to achieve what we want it to do, like pregnancy.