Malabsorption of levothyroxine due to Enterobius vermicularis

Abstract

Objectives: Poor compliance with the therapy regime is the most common cause of failure of levothyroxine therapy, however several cases of malabsorption, especially in patients with celiac disease were described. In our patient enterobiasis seems to be the most likely cause of therapy failure. Methods: A 37 year old female patient with autoimmune thyroiditis and elevated TSH while on 400µg Levothyroxin is presented. Results: Poor comliance seems the most obvious cause when a rise in free T4 could be demonstrated in a resorption test. There was no evidence for celiac disease. Eventually a stool sample, which was taken due to intermittend abdominal compaints, showed large amounts on enterobius vermicularis (eggs an intact nematodes). After treatment with mebendazol the patient became hyperthyroid and the dose of levothyroxine has to be tapered to 100µg leading to stable euthyroidism. Conclusion: Malabsortion of Levothyroxin due to Enterobius vermicularis should be suspected as a rare cause of therapy failure in hypothyroid subjects.