SAT-617 Lingual Thyroid Gland: It's Time for Awareness

Abstract

Lingual thyroid gland is an unusual embryological abnormality that occurs when the thyroid gland fails to migrate from the foramen cecum to the pretracheal position. It manifests in 1: 100,000 - 1: 300,000 subjects of the general population, making this diagnosis extremely rare. The typical presentation is asymptomatic, but when symptoms develop the most commonly seen are odynophagia, dysphagia, dyspnea and dysphonia. Due to the rarity of this condition it is often overlooked, resulting in complications later in life. We present a case of lingual thyroid gland in a Hispanic female patient complaining of voice changes. A 41-year-old female patient with no past medical history presented to the Otolaryngology - Head and Neck Surgery clinics with a three week history of dysphonia and odynophagia. The patient denied any constitutional symptoms or associated symptoms of thyroid dysfunction. Fiber optic flexible indirect laryngoscopy was used to examine patient’s airway, and a mass highly suspicious for an ectopic thyroid gland was identified at the base of tongue. A Neck CT scan and a thyroid ultrasound were performed, demonstrating the absence of thyroid tissue in its normal anatomic position without lymphadenopathy. Thyroid scan revealed the presence of a lingual thyroid gland. This structure was causing mass effect on esophagus and vocal cords, resulting in dysphagia and dysphonia. The patient was referred to the Endocrine service where she was found to have a TSH of 6.3 mIU/L, Total T4: 6.89 mIU/L, and a negative anti TPO antibody, which is remarkable for Subclinical Hypothyroidism not requiring medical management. However, on a close follow up visit, her TSH increased to 9.60 mIU/L and Free T4 was found at 0.9 mIU/L, leading us to a diagnosis of overt Hypothyroidism requiring medical management. Lingual Thyroid Gland is an extremely rare anatomical variation that might be often overlooked. Literature demonstrates that in 70% of the cases reported, the lingual thyroid appeared to be the only functioning thyroid tissue. It is most often diagnosed during puberty, pregnancy, or menopause when the increase in thyroid hormone requirement and subsequent increase in TSH causes thyroid tissue hypertrophy and therefore obstructive symptoms. Levothyroxine treatment has caused marked reduction in the size of the lingual thyroid potentially avoiding the need of a surgical intervention or the need to exclude malignancy. A recent systematic review found 28 cases of Lingual Thyroid Carcinoma (LTC). There are no distinguishing clinical findings to differentiate benign lingual thyroid from LTC. However, in the setting of a well-defined, smooth, benign-appearing mass and neck CT scan without evidence of mass extension or lymphadenopathy, a conservative approach could be pursued with follow up evaluation of the mass after hormone replacement therapy.