<p>Although GnRH agonists are widely used for the treatment of uterine fibroids, the risk of cerebrovascular/cardiovascular events and venous thrombosis is described in the package insert. In the present case, a patient with bilateral internal carotid artery stenosis and submucosal myoma with severe anemia was treated with a GnRH antagonist rather than a GnRH agonist. The patient was 47 years old, had two pregnancies and two deliveries (two vaginal deliveries). She came to our clinic with complaints of excessive menstruation and anemia. On initial examination, transvaginal ultrasonography showed a mass of 90 mm in diameter that was thought to be a submucosal myoma. Pelvic MRI revealed a mass of 86 mm in diameter in the uterine corpus, which was diagnosed as submucosal myoma. Blood tests showed severe anemia with Hb 5.4 g/dl, and the patient was decided to undergo surgical treatment. In addition, head MRA showed severe stenosis of bilateral internal carotid arteries, and the patient was treated only with iron injection without estrogen-progesterone combination, but the anemia did not improve. Thereafter, an oral GnRH antagonist (Relugolix) 40 mg/day was started, and after administration, genital bleeding stopped and anemia improved to Hb12.3 g/dl. The diameter of the tumor mass was reduced to about 60 mm in length by MRI immediately before surgery. As for the surgical technique, we explained that laparotomy was safer than laparoscopy because of the adverse effect on cerebral circulation caused by the low head position of laparoscopy. However, the patient strongly desired laparoscopic surgery, so we performed a laparoscopic total hysterectomy, and the patient was discharged on the fifth postoperative day. Although GnRH agonists are known to increase the risk of thromboembolism in patients with prostate cancer, only five cases of thromboembolism associated with the use of GnRH agonists for benign gynecological diseases have been reported so far. Considering the description in the package insert, GnRH antagonist rather than GnRH agonist may be a promising option in patients with high risk of cerebral infarction as in the present case, but whether the risk of thromboembolism is truly lower with GnRH antagonist in benign gynecological diseases requires further evidence in a large number of cases. However, whether the use of GnRH antagonists is truly associated with a lower risk of thromboembolism in benign gynecological diseases requires further evidence from a large number of patients. [Adv Obstet Gynecol, 74(1) : 27-31, 2022 (R4.2)]</p>