A 26 year old woman presented with a two year history of palpitations, heat intolerance, fatigue, tremors, and an increase in neck size. Her physical examination revealed tachycardia, lid lag and an enlarged, non-tender thyroid gland. Oral cavity examination was completely normal. There was no proptosis. Her thyroid function tests and iodine-123 scan and uptake were consistent with Graves' disease. Thyroid stimulating antibody concentration was negative. Incidentally, a small area of uptake was seen superior to the eutopic thyroid which corresponded to the area at the posterior aspect of the tongue and was consistent with the presence of lingual thyroid (see figs 1A and B). There was no salivary gland uptake. The patient underwent successful iodine-131 ablation therapy.

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Figure 1

Iodine-123 uptake scan; arrows show presence of lingual thyroid; (A) anterior and (B) lateral views.

Ectopic thyroid tissue results due to abnormal migration of the thyroid gland from the base of the tongue to its normal pre-tracheal position. The prevalence of ectopic thyroid tissue is between 7%–10% with lingual thyroid accounting for 90% of such cases. Mutations in thyroid transcription factors 1 and 2 have been found in patients with thyroid agenesis and ectopic thyroid tissue. Lingual thyroid lies on the posterior aspect of the tongue and oral examination is usually normal. Invasive fibre optic laryngoscopy is generally needed to visualise the ectopic tissue in such location. Our patient refused any invasive procedure.