Elevated serum CA 19-9 in association with Hashimoto thyroiditis.

Tumour markers are widely used in clinical practice. Elevated tumour markers can be observed in both malignant and benign conditions. Therefore, it is important for clinicians to be aware of the association of tumour markers with various disorders so that unnecessary investigations can be avoided without missing the malignant disorders. A 58-year-old woman who presented with weight loss and elevated carbohydrate antigen 19-9 (CA19-9) was referred to our hospital for evaluation and was subsequently diagnosed with Hashimoto thyroiditis. Investigations for underlying malignancy were negative. The CA19-9 level normalised subsequently, with restoration of the euthyroid state.