Endocrine Abstracts

Introduction: Targeted therapies and monoclonal antibodies are known to trigger thyroid autoimmunity. No case of autoimmune thyroid disease with mepolizumab, an anti-IL-5 monoclonal antibody, is reported in the literature. In this case report, we present a case of Graves’ disease that recurred after Mepolizumab treatment.

Case: A 74-year-old male patient was referred to the endocrinology outpatient clinic upon detection of hyperthyroidism on 11/2021. The patient, who had known aortic valve replacement, allergic asthma, and benign prostatic hyperplasia, was using warfarin 1×5 mg, atorvastatin 1×20 mg, inhaler salmeterol, 1×5 mg levocetirizine and 1×8 mg silodesin. In the patient’s examinations, TSH <0.008 mU/l, free T4:3.94 ng/dl, free T3:11.99 ng/l, anti-tg:2.4 IU/ml, and TSH receptor antibody (TRAB):6.77 IU/l (<1.5 IU). /l) was seen. On electrocardiography, his pulse was 98 beats/minute, and his rhythm was normal sinus rhythm. While no nodule was detected in the patient’s thyroid ultrasonography, bilateral parenchymal heterogeneous and sparse patchy hypoechoic areas were observed. Color flow doppler pattern was observed as 2 in thyroid doppler. The patient, who had no history of recent contrast exposure or amiodarone use, was evaluated as having Graves’ disease, and methimazole 3x5 mg and propranolol 2x20 mg were started. No signs of ophthalmopathy were detected in the eye examination performed at the time of diagnosis. After one month, propranolol was discontinued, and methimazole dosage was adjusted, and periodic checks were scheduled. On 05/2023, in the 19th month of treatment, while receiving methimazole 1×2.5 mg treatment, TSH was measured:2.4 mU/l, free T4:1.04 ng/dl, free T3:3.62 ng/l, thyroid stimulating immunoglobulin was 0.52 IU/l (0.1-0.55 IU/l). The treatment was discontinued at this point. In the follow-ups performed one month and two months later, it was observed that the patient was euthyroid. On 07/2023, as the patient’s complaints about allergic asthma increased, the pulmonologist started Mepolizumab to be administered 100 mg subcutaneously once a month. On 09/2023, after the patient received two doses of mepolizumab, TSH:0.02 mU/l, free T4:1.86, and free T3:4.68 ng/l were observed in the controls performed in our outpatient clinic, and the patient was started on methimazole 1×5 mg again. The patient, who was evaluated as having a relapse of Graves disease, was assessed in a multidisciplinary council, and radioactive iodine treatment was planned.

Conclusion: Thyroid autoimmunity may be triggered after Mepolizumab, an anti-IL-5 monoclonal antibody. Patients receiving this treatment should also be followed in this respect.