Letrozole is classified as an aromatase inhibitor, which means it reduces the formation of estradiol from testosterone. As a result, your pituitary will release more FSH and LH to stimulate the ovaries to make follicles and ovulate. Letrozole is now a relatively new treatment for breast cancer. It is being used off label to induce or augment ovulation, though it is NOT FDA approved for ovulation induction. It is also used in combination with FSH to augment or increase your ovary’s response to this medication. It is common to see a markedly reduced estradiol level, despite good follicle development on ultrasound. Your physician may ask you to obtain an ultrasound on day 12 of treatment.