August 28, 2007
Clomid works by tricking your brain (hypothalamus primarily) into thinking there is no estrogen around. Your hypothalamus will respond by producing more GnRH hormone that’ll trigger a greater production of FSH/LH from the pituitary, stimulating a follicle to grow in the ovary for those who are not ovulating.
Letrozole (Femara) works by stopping the production of estrogen. Your hypothalamus recognizes this decrease in Estrogen, and purposely creates more hormones in the same fashion as Clomid to help the ovary make a follicle.
Injectable Gonadotropins come in two forms: urinary or recombinant products. Urinary gonadotropins (Bravelle, Menopur, Repronex) are derived from the urine of postmenopausal nuns in monasteries (yep, that’s correct) and are highly filtered and purified for their FSH and LH and made into a powdered form. Recombinant gonadotropins (Gonal-F, Follistim) are genetically engineered in a laboratory and are “pure” FSH. Luveris is a recombinant injectable form of LH.
Human Chorionic Gonadotopin (hCG) can be purchased as either a urinary or recombinant product. We usually use hCG at high doses once the follicle(s) are mature to induce ovulation just like the human body would. Now, we use hCG instead of LH (like your body does) because they work the same and hCG is much less expensive than if we used LH.
Your RE can dose your gonadotropins according to your reproductive history. Usually the higher the gonadotropins dose, the greater the likelihood of “rescuing” more than one follicle. Remember, these follicles were going to be lost since your brain only selects one out each month, with the following month bringing about a whole new cohort of follicles from which again, only one would have been selected out by your brain.
Some of you may be on Lupron (GnRH agonist) which works by eventually shutting down the brain’s (hypothalamus) production of GnRH. Therefore, the pituitary will not produce any FSH or LH resulting in no ovarian stimulation. Your body senses this immediate lack of no follicular development/Estrogen and thus believes it is in a menopausal state, giving you all of these symptoms. It usually takes Lupron upto a week before it shuts the production of GnRH and once Lupron is stopped, these symptoms are truly reversible.
Cetrotide or Antagon are GnRH antagonists and work like Lupron, except that their action is immediate, and doesn’t take a week for this to occur. The primary reason Lupron, Antagon, or Cetrotide is given is so that your body doesn’t on its own do things that would ruin a stimulation cycle, such as your brain prematurely secreting an abundance of LH…Not fun if you just paid $10,000 for IVF and then the doc says “sorry, your body didn’t cooperate with us so we have to cancel the cycle”.