Breast cancer drugs for infertility treatment?

My doctor prescribed a medicine called letrozole to help treat my fertility issues but the insert from the pharmacy and manufacturer says it’s for breast cancer treatment. What’s that all about?

Femara (generic name, letrozole) is a commonly used breast cancer drug that is also frequently used by fertility specialists and obgyn doctors to stimulate egg production in women who have been unable to get pregnant. That sounds kind of bizarre, using a breast cancer drug to make you ovulate, but actually, using a drug breast cancer to stimulation makes a lot of sense if you understand how fertility pills work. 

For years, clomiphene (Clomid) was the main oral medication used to stimulate ovulation in fertility patients. Clomid is a type of drug called a SERM that works by blocking some of the effects of estrogen, one of the most important female reproductive hormones. The brain, pituitary gland and ovary rely on a series of hormones to speak to each to each other and regulate the ovary using a system called feedback. When clomiphene blocks estrogen, this feedback goes away and that makes the brain and pituitary gland think that the ovaries are not working and the pituitary gland starts producing hormones such as FSH (follicle stimulating hormone) that give your ovary a little kickstart. Interestingly, tamoxifen, another SERM commonly used drug to prevent the recurrence of breast cancer does exactly the same thing and some doctors use it for this for fertility treatment as well.

The letrozole that we prescribe works a little bit differently. This medication which is also taken in the early part of the cycle, blocks an enzyme in your body that turns testosterone into estrogen. It is not chemotherapy. For women with certain types of breast cancer, low estrogen levels lower this risk of recurrence of the cancer. When used in fertility patients, the lower estrogen levels encourage the production of hormones that stimulate egg growth, but it does so more gently than clomiphene.So why would your doctor consider using letrozole over clomiphene?
It turns out that letrozole does offer some benefits over clomiphene including:

  • similar pregnancy rates to clomiphene
  • fewer multiple births
  • fewer annoying side effects such as hot flashes, beaches and mood swings
  • may help more with endometriosis

Both letrozole and clomiphene are very effective when used properly, and the decision on which one to use, is a discussion best had with your fertility specialist or gynecologist.

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