A 45-year-old woman presented with recurrent episodes of diarrhoea, nausea, vomiting and abdominal pain. Investigations, including routine blood tests, gastroscopy with duodenal biopsy, colonoscopy and abdominal computed tomography (CT) scanning, failed to find a cause of these symptoms. Routine blood tests were repeated and included thyroid function tests. The latter confirmed a diagnosis of primary hypothyroidism. After initiating thyroid hormone replacement therapy, all of the patient’s symptoms resolved. She remains well and asymptomatic to date.