Two Cases of Transiently Elevated Serum CEA Levels in Severe Hypothyroidism without Goiter

Carcinoembryonic antigen (CEA), the level of which is known to increase in both patients with gastrointestinal cancers and those with non-neoplastic conditions, is one of the most widely-used tumor markers. Hypothyroidism is a common endocrinological disorder in which CEA levels can rise, and is sometimes overlooked as a diagnosis in the absence of typical symptoms or thyroid enlargement. We report the cases of two patients with non-goiterous severe hypothyroidism with markedly elevated CEA levels that effectively decreased with levothyroxine replacement therapy alone. Hypothyroidism should be considered as an important cause of unexplained high serum CEA levels in order to avoid unnecessary medical examination.