The Ins and Outs of Fertility Medications: How They Work Within the Body

Laura Morrissey, RN, BSN

4 min read

During fertility treatments, there are numerous medications with different names and functions, but have you ever wondered what all those medications are doing inside your body and what makes them work? Here are some of the main medication types and how they function during treatment.

Gonadotropins: These Medications Stimulate Follicle Growth

There are two types of gonadotropins used in fertility treatments: follicle stimulating hormones and menotropins. They are commonly used in IVF and egg freezing, and occasionally used in IUI and timed intercourse.

Follicle Stimulating Hormone (FSH) 

Common brand names: Follistim and Gonal-F 

FSH medications are used to mimic the action of the follicle stimulating hormone (FSH), which is naturally produced in the body by the pituitary gland. When the pituitary gland secretes FSH, it stimulates the ovaries to grow a follicle and egg to maturity so it can eventually ovulate. Adding in additional FSH through medications like Follistim and Gonal-F causes the body to stimulate multiple follicles to grow, with the goal of having multiple eggs grow in order to be retrieved in IVF and egg freezing cycles. 

Menotropin (HMG)  

Common brand name: Menopur

Menopur is a combination of FSH and luteinizing hormone (LH). It works in conjunction with medications like Follistim and Gonal-F for optimal response during ovarian stimulation cycles. The small and steady source of LH from Menopur helps the follicles grow. LH stimulates changes in the structure and function of the egg cell that allow it to progress towards maturity in preparation for ovulation or egg retrieval.

These Medications Prevent You From Ovulating Before an Egg Retrieval

An egg retrieval occurs at the end of an egg freezing or IVF cycle.

Gonadotropin releasing hormone (GnRH) antagonist 

Common brand names: Ganirelix, Cetrotide, and Fyremadel

GnRH antagonists are used to block the production of LH by interfering with the binding of GnRH to its receptors on the pituitary gland. Because LH is the hormone that triggers ovulation, the suppression of an Luteinizing Hormone Surge prevents the eggs that are growing in the ovaries from ovulating before the egg retrieval. Usually GnRH antagonists are started in the middle of the ovarian stimulation cycle and continued through the trigger shot. 

Gonadotropin releasing hormone (GnRH) agonist 

Common brand name: Lupron

Lupron (leuprolide acetate), when used as an agonist, is started at the beginning of ovarian stimulation. Its initial effect is to cause a surge in FSH and LH from the pituitary gland, and that surge causes the follicles in the ovaries to start growing. Then, after the initial hormone surge, Lupron suppresses the release of these hormones, which prevents premature ovulation through the absence of an LH surge. Lupron is administered daily during the cycle alongside FSH and HMG, which act to continuously stimulate follicle growth.

Additional Medications That Can Be Added During Ovarian Stimulation

These medications are used during the ovarian stimulation portion of egg freezing and IVF cycles.

Human Growth Hormone 

Common brand name: Omnitrope 

Omnitrope is used during ovarian stimulation for people who have issues with egg quality or poor ovarian reserve, as well as for other populations who have unexplained struggles with fertility. The mechanism of action is not perfectly understood. Growth hormone has shown to improve increased implantation and embryo development according to some studies. Omnitrope is a medication prescribed as a supplement to other stimulation medications and is administered as a daily subcutaneous injection.

Low dose hCG 

Compounded by the pharmacy 

Low dose hCG is a subcutaneous injection that is used to supplement the effectiveness of FSH and menotropin medications. Low dose hCG is a specific dilution of hCG that is compounded by the pharmacy. This small continuous dose of hCG mimics the effects of luteinizing hormone, which enhances the effectiveness of FSH and aims to get a better response from the ovaries during stimulation. 

Trigger Shots

The last and seemingly most intimidating medication used in ovarian stimulation is the trigger shot that prepares the eggs for retrieval. There are 2 types of trigger shots, Lupron and hCG. These medications can be used on their own or in combination with one another. 

Because the trigger comes with a lot of new and different information, we wrote a separate article all about it. You can check it out here: Fertility Treatment: The Trigger Shot Explained.