Endocrine Abstracts

JOINT2592

Introduction: Synthetic antithyroid drugs, notably methimazole, carbimazole, and propylthiouracil (PTU), are commonly used medications for the treatment of hyperthyroidism. Although these drugs are generally effective, they can sometimes cause adverse effects and cross-reactions, meaning allergic or toxic reactions to different but chemically similar medications.

Observation: A 37-year-old female patient consulted for signs of hyperthyroidism: palpitations, significant unquantified weight loss deemed important. A thyroid panel was requested, revealing low TSH levels with a T4 level of 43.07 pmol/l. The cervical ultrasound suggested Graves’ disease, with positive Anti-TSH receptor antibodies. The patient was initially placed on Methimazole 40 mg; after a few days, she developed skin lesions (urticaria), prompting a change in treatment to Carbimazole along with the initiation of antihistamine therapy, but without improvement in the allergic reactions. After achieving euthyroidism, the patient underwent total thyroidectomy without postoperative incidents.

Discussion: Cross-reactions between synthetic antithyroid drugs can be explained by the chemical similarity among these medications. Methimazole and carbimazole, for example, are closely related. Although rare, cross-reactions pose a significant clinical challenge. Patients who develop adverse reactions to one antithyroid drug are at an increased risk of reacting similarly to other drugs in the same class. Management of cross-reactions between synthetic antithyroid drugs requires a careful and personalized approach.

Conclusion: Cross-reactions between synthetic antithyroid drugs, although varied among different molecules, necessitate careful evaluation and appropriate management. In cases of intolerance or hypersensitivity, alternatives such as propylthiouracil, radioactive iodine, or surgery should be considered. Increased vigilance can help limit risks and optimize the treatment of patients with hyperthyroidism.