The Menstrual Cycle, Ovulation, & Fertility Medications

It is your brain (hypothalamus and pituitary) that produces hormones that signal the ovary to produce and usually select out only one follicle (the sac that contains the egg) out of many per month once your period starts. The hypothalamus secretes GnRH hormone that triggers the pituitary to secrete both FSH and LH hormones. It is the FSH and LH hormones that help the ovary create and grow a follicle. Once the follicle is “mature”, the follicle tells the brain (the pituitary in particular) that it is ready to be ovulated through the sustained production of a large amount of estrogen (this is what gives you the egg white cervical mucus). The pituitary reads this and in response, secretes a large amount of the ovulatory hormone (LH) to allow the follicle to ovulate the egg about 36 hours later. Your OPK kits detect this “LH surge” and that’s how we know you’re going to ovulate. Once you have ovulated, the remaining follicle turns into the Corpus Luteum that creates lots of Progesterone for the next 14 days. It is the Progesterone that creates your rise in body temperature that is detected on BBTs and gives you many types of symptoms, such as breast tenderness. The Corpus Luteum only lasts for 14 days and unless you’re pregnant, will die off and stopping the production of Progesterone and Estrogen. Once your uterus senses that there’s no more Progesterone or Estrogen, it sheds off it’s lining (a process commonly known as a period) and the cycle repeats itself.

MEDICATIONS:

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”.