Hi, Thanks for posting in HCM. I understand your concern. Letrozole is an oral non-steroidal aromatase inhibitor , which is used for the treatment of hormonal-responsive breast cancer after surgery. It is administered to treat local or metastatic breast cancer that is hormone receptor positive. Letrozole is also used for ovarian stimulation and is preferred by some doctors to Clomifene as it has lesser side effects and lesser incidence of multiple gestation. Common side effects are sweating, hot flashes, joint pain and fatigue. It is not known to cause delay in periods. Hence, you need to get your serum FSH and LH hormonal levels along with thyroid profile checked to know what could be the cause for the delay. Kindly consult Gynecologist for appropriate management. Hope the information provided would be helpful. All the best.