Fertility Blog

Science Pulse Extra - How Letrozole Works

Infertility clinics around the country as well as OB/GYN centers are reporting favorable results from letrozole for extremely specific treatment options for a small percentage of patients. It is by no means a medication that is or will become standard until more studies are conducted. Both clomiphene citrate (marketed as Clomid) and letrozole (marketed as Femara) are oral medications used to stimulate ovulation. Letrozole was originally developed for breast cancer treatment, as certain types of breast cancer cells slow their growth in response to decreasing estrogen levels. Letrozole falls in the category of drugs known as non-steroidal aromatase inhibitors, meaning it is highly specific in suppressing estrogen synthesis. Aromatase is an important enzyme prompting the creation of estrogen. If the body makes less estrogen at the start of the cycle, a woman's FSH level increases and ovulation is stimulated or enhanced. Letrozole is considered as an alternative to Clomid for women undergoing ovulation induction especially for women whose uterine lining may be thinned out by Clomid. As an anti-estrogen, Clomid can limit the development of the endometrial lining making it difficult for an embryo to implant. For reasons that are not yet quite clear, letrozole appears less likely to affect the uterine lining, perhaps because of a short half-life and therefore, a shorter effect on estrogen production. Letrozole has a short life span in the body whereas Clomid can last for 4-6 weeks following an oral dose. For more information, see A Closer Look At Letrozole -- Carolyn Givens, MD