A 30-year-old woman treated for biological hypothyroidism with L-thyroxine (LT4) presented with a suspicion of lingual thyroid when head and neck examination discovered a lump on the tongue, confirmed by cervical ultrasound (US) findings. The scintigraphic study performed under LT4 (87.5 μg/day), after injections of recombinant human thyroid-stimulating hormone (TSH), and 2 h after injection of 37 MBq of 123I, on a single photon emission computed tomography (SPECT)/CT gamma camera (Siemens Symbia T2) showed an isolated high cervical uptake corresponding to the sublingual thyroid [1]. SPECT/CT images provided anatomical details: larger diameter of 22 mm and no functional glandular tissue in central cervical position (a). Whole-body scan did not show any pathological iodine uptake, especially in the pelvic area (b). This acquisition allowed the realization of 3-D reconstructions (c).

Hypothyroidism represents the main clinical symptom of ectopic thyroid [2]. Other complications are haemorrhage and superior airway obstruction with dyspnoea and/or dysphagia.

The diagnosis of lingual thyroid relies on clinical examination and cervical US that identifies a vacant thyroid site and a lump on the tongue base with a structure similar to thyroid tissue [3]. 123I scintigraphy with a hybrid camera provides functional and anatomical images, and looks for other locations of ectopic thyroid tissue.