Endocrine Abstracts

Context: A lingual thyroid is a relatively rare clinical entity. It is the most common subtype of ectopic thyroid. An ectopic thyroid is caused by an aberrant descent of the thyroid gland from the foramen caecum to its normal pretracheal position during embryogenesis. A lingual thyroid is located at the midline of the tongue base. It can be asymptomatic, but it may also cause dysphagia, upper airway obstruction, haemorrhage or dysphonia. Moreover, about 70% of patients with lingual thyroid have hypothyroidism.

Case report: A 29-year-old female patient was referred for mild primary hypothyroidism (TSH 9.96 mU/l and FT4 0.86 ng/dl). She was asymptomatic and had no medical history. As there were no biochemical signs of auto-immunity, an ultrasonography was performed in search of an hypoechoic hypervascular thyroid. This revealed the absence of any visible thyroid gland tissue, raising the suspicion of an ectopic thyroid. A Tc-99 SPECT-CT was performed and revealed a lingual thyroid (uptake at the base of the tongue and no thyroid bed uptake; and a visible mass on CT). Laryngoscopy confirmed a spherical mass (3 cm in diameter) at the midline of the tongue base (Figure 1A). No mucosal lesions could be seen. The vocal cord mobility was symmetrical.

Levothyroxine treatment was initiated to treat the hypothyroidism and to prevent further growth of the lingual thyroid, aiming at a TSH 0.3–2 mU/l. No surgical intervention was planned since the patient did not suffer from dysphagia or dyspnoea.

Laryngoscopic re-evaluation after 2 years of treatment with levothyroxine showed stable dimensions of the lingual thyroid. However, after 7 years of treatment, the size of the lingual thyroid was significantly smaller (2 cm) (Figure 1B).

Conclusion: Observation and levothyroxine treatment aiming at a low normal TSH was effective and may be a good alternative to surgery in a- or oligosymptomatic patients with lingual thyroid.

Figure 1 Laryngoscopic follow-up of the lingual thyroid gland. (A) At diagnosis. (B) After 7 years of treatment.

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