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SMART Blog July – Why we use injectable fertility drugs


By Dr Nikolaos Tsampras, one of our Clinical Fellows

Ever wondered about the injections that women undergoing IVF have to administer to themselves? Here, Dr Tsampras describes the different types of medication, why it is used and what to look out for during treatment.

What are gonadotrophins?

Gonadotropins are injectable fertility medicines, containing follicle-stimulating hormone (FSH) alone or combined with luteinizing hormone (LH). FSH and LH are present in our bodies naturally, in both men and women. During a natural menstrual cycle, both FSH and LH are produced by the pituitary gland in the brain to naturally stimulate the ovaries to produce a single egg each month.  When FSH (with or without LH) is given as an injection, it works directly on the ovaries to make multiple follicles (the fluid-filled areas within the ovary that contain eggs).

Gonadotropins are used during fertility treatments such as In Vitro Fertilization (IVF).  Injections of gonadotropins are started early in the menstrual cycle to cause multiple eggs to grow and mature. We perform close monitoring of patients who are using these medications in order to know when the follicles have reached a size that tells us that they are ready for collection. Another reason for monitoring is to anticipate the side effects of this treatment.

When the ultrasound monitoring indicates that the follicles are ready for collection, another injectable medication is used to mature the eggs. This is called Human Chorionic Gonadotropin or HCG. Sometimes you will hear it referred to as a ‘trigger’ injection. 

Why are Gonadotrophins used in fertility treatments?

When FSH is given in larger amounts than would occur in a natural menstrual cycle it results in more than one egg being ripened and matured.

Sometimes if you are not ovulating, Gonadotrophins are given in the amount roughly equal to that of a natural menstrual cycle and this is called ovulation induction.

Gonadotrophins are commonly used in IVF cycles. The intention here is to develop several eggs with the aim of fertilizing them outside the body. The reason why so many eggs are necessary is that the process of IVF is relatively inefficient and the more eggs that are available for fertilization, the more likely pregnancy is to occur. Having several eggs available for fertilization hopefully results in good-quality embryos from which our scientists can select the ‘best’ ones for transfer.

Gonadotrophins have been used in fertility treatments for more than 30 years. They were initially prepared from the pituitary glands of deceased people. This was very expensive and gave FSH of variable quality. This is no longer available for use in UK.

The second preparation was obtained from the urine of post-menopausal women. It was purified and used for injection. These were given as deep injections into the muscle. The most modern urine derived preparations are highly purified and can be administered subcutaneously. These contain FSH and LH activity.

The most modern preparation which is commonly used today is recombinant FSH. This uses genetic technology. It is therefore relatively pure. This drug is not from a human or animal tissue source and can be given as a subcutaneous injection rather like that which people with diabetes have.

All products have the same expected pregnancy rates, although a minority of patients will benefit from an LH-containing product. 

What are some of the potential side effects of gonadotropins?

Ovarian Hyperstimulation Syndrome (OHSS)

The main worry is a condition called Ovarian Hyperstimulation Syndrome, or OHSS, in which the ovaries respond excessively to stimulation, causing swelling of your tummy with nausea and other symptoms. Monitoring may help us predict if you are very likely to develop OHSS and we can then suggest measures to take to prevent it. (More information about OHSS can be found in our podcast and information session presentation).

OHSS is characterized by enlarged ovaries and fluid accumulation in the abdomen. Although a mild form occurs in up to 20% of cycles and results in some discomfort, the severe form occurs approximately to 1% of the patients. Over the years, multiple strategies have been developed, in order to prevent OHSS. Active monitoring by doctors familiar with the use of FSH is a key to reduce OHSS incidence.

Multiple Gestation

During treatment with gonadotropins, up to 20% of pregnancies are associated with multiple implantations (twins or more), which only occur in 1% to 2% of naturally occurring pregnancies. The increased risk of multiple pregnancies is related to the number of eggs that are stimulated during an ovulation induction cycle or to the number of embryos transferred in an IVF cycle. We aim to keep your risk of multiple pregnancy at a low level, while still achieving a good chance of conception. For this purpose, our scientists follow an evidence-based algorithm and will recommend the number of embryos they think is best to transfer. More information about multiple pregnancy and fertility treatment can be found at

Ectopic Pregnancies

While ectopic pregnancies occur in 1% to 2% of naturally occurring pregnancies, in IVF cycles the rate is slightly increased. Ectopic pregnancies can be a life threatening condition and require treatment with medication or surgery. They are specially common in women with a history of tubal damage.

Gonadotropins and Cancer

Current studies have shown no increase in any cancers with the use of gonadotrophins. 

 Local or Generalized Reactions

In some women, the injection may cause a local skin irritation. It is extremely rare to have an allergy to medication. Some women may experience breast tenderness, headaches, or mood swings from the gonadotropins.