Simple Breakdown of Fertility Meds

I hope to break down the different meds and their uses in a way that helps you understand why you are taking what you are taking at the different times in their cycles.

A very simplified explanation of how the body works – during your period, your ovaries ideally have a lot of tiny follicles all vying to be the one that gets to ovulate. Your body releases FSH, follicle stimulating hormone, to tell the ovary to grow the follicle. As it grows, it releases estradiol, which in turn tells the body to slow the release of FSH. One follicle (usually) is selected as the winner and grows to maturity while the rest die off. The mature follicle releases enough estradiol to tell your body it is ready for it’s big debut which triggers your body to flood your system with LH, luteinizing hormone, which will perform the final polishing on the follicle and then launch the egg out for it’s big shot at fertilization.

When you do medicated cycles, you are typically trying to get around that natural process and get your ovaries to go into overdrive and make more follicles. You also have to be careful you don’t ovulate those prior to their maturity or your IVF retrieval, IUI, etc. All of this is accomplished with various drugs given in various ways. As I said, there are so many different ways to do a cycle. It is called ART, as in assisted reproductive technology, but creating the best med protocol for you is truly a work of art!


Stimulation meds are meds used to push the ovary to grow more than one follicle per cycle. They can be oral meds, like clomid or letrazole. Clomid blocks estrogen receptors and letrazole stunts the production of estrogen, so when on either of these, your body is likely to be releasing more and more of your own FSH, looking for that estradiol message back to let it know a follicle is growing. Because it releases more FSH than normal, you are likely to have more than your normal 1 follicle growing.

Gonal-F and Follistim (in the US) are injectable FSH. Just like you imagine, they work the same way your own FSH works, stimulating the ovary to grow more follicles. Menopur is an injectable that contains both FSH and LH.

LH blockers:

Stimulation meds are used in the follicular phase and typically given for 5 to 12 days, with the sole purpose of helping to grow follicles.

Imagine you have multiple follicles growing and your estradiol is getting nice and high. Your body would normally see the high estradiol and start the ovulation process, which you want to avoid, so you need something to block your own LH surge. There are two types of drugs used to do this, an agonist like Lupron or an antagonist like ganirilex or cetrotide.

Lupron may be started before your cycle and continued throughout. This is typically called the long Lupron or down regulation protocol and most of us women with DOR never even see that one, as it can be suppressive. Lupron can also be given in a smaller dose in a “flare” protocol. The flare is referring to the action of the Lupron to first cause a huge flood of your own FSH and LH, which helps get follicles growing, then a few days in, the Lupron starts suppressing.

Antagonists are typically given when your biggest follicle is around 14mm. The key here is to start it before your LH is creeping up too much, but it is usually started mid to late follicular phase. Typically you take an antagonist only 5 days or less, leading up to your trigger shot


Triggers are used to finish the maturation of the follicle and then either force ovulation in the case of IUI or timed intercourse, or time egg retrieval. Triggers are generally usually HCG, the pregnancy hormones, common names are Pregnyl or Ovidrel. You can also be triggered with Lupron. Lupron when given as a trigger will cause your own LH to release. A little less common is a nasal spray that can be used as a trigger, Synarel. It also causes a release of your own LH.

So if you are following, we have stim meds and LH blockers taken during the follicular phase to grow as many follicles as we can but not ovulate them before we are ready. Then we have a trigger med to cause the ovulation or time the retrieval.

Luteal Phase:

Post IUI, or retrieval we have the luteal phase. Generally when you ovulate your follicle that the egg ruptured from forms a corpus luteum cyst which produces progesterone. Progesterone is needed to support a pregnancy. If by day 10 or 12, there is no pregnancy, the lining of the endometrium begins to breakdown to shed, progesterone drops and your period starts. If there is a pregnancy, the hcg released by the embryo will “rescue” the corpus luteum and let it know to stay put and continue to release the progesterone.

In IVF, retrieving the follicles disrupts this natural process and may result in no or inadequate corpus luteum, so for the luteal phase, most are put on some sort of progesterone treatment. It may be an injection or vaginal gel like Crinone or suppository like Endometrin. Many times women who do IUI or TI are also put on prog for good measure. And luteal support may also include estrogen in the form of patches or pills.

So now we covered a full cycle sort of… What about pre-cycle? You can start a fertility on your period, whenever it comes. We call that a natural start. But most are timed or primed.


You may take birth control pills pre-cycle. They are helpful to time the cycle, they quiet the ovaries and many believe help the body respond to the stimulation meds more. Women with DOR may find the opposite is true for them and BCP are too suppressive. You may do estrogen priming pre-cycle. It can also help with timing and is thought to help the follicles grow closer in size instead of having a lead follicle, as well as to create a better environment in which the follicles can grow.

There are other priming protocols, including using estrogen with antagonist, using testosterone or even using human growth hormone.

I hope this very generalized explanation is helpful as you look through your box of meds or try to make sense of a protocol or calendar. There is no right way to do this, and unfortunately it is trial and error. Your doctor will hopefully create a personalized plan for you based on all available data then tweak it after each try as they are collecting more data about how you respond.