Endocrine · Year 2 · from Endocrine
Case 2: Lingual Thyroid
Patient Demographics
- Age: 16 years
- Sex: Female
- Occupation: High school student
Chief Complaint
"I feel like there's something in the back of my throat, and I sometimes have trouble swallowing."
History of Present Illness
A 16-year-old girl presents with a 6-month history of sensation of a mass in her throat, mild dysphagia with solid foods, and occasional gagging. She has not had voice changes, pain, or bleeding. She reports that she has always been somewhat tired and has had difficulty with weight despite diet and exercise. She started menstruating at age 14 but her periods have been irregular and infrequent. On review of systems, she notes constipation, dry skin, and cold intolerance.
Physical Examination
- Vital Signs: BP 108/70 mmHg, HR 58 bpm
- General: Mildly overweight, appears fatigued
- HEENT:
- Oral cavity: Smooth, rounded, pink-red mass at base of tongue (posterior midline)
- Mass approximately 2 cm, non-tender, covered with normal mucosa
- Neck: Thyroid gland NOT palpable in normal pre-tracheal position
- Skin: Dry, cool
- Reflexes: Delayed relaxation phase
Workup
- Laboratory Studies:
- TSH: 48 mIU/L (markedly elevated)
- Free T4: 0.4 ng/dL (low)
- Anti-TPO antibodies: Negative
- Ultrasound Neck: No thyroid tissue identified in normal cervical location
- Thyroid Scintigraphy (I-123 or Tc-99m): Uptake only at the base of tongue; no cervical thyroid tissue
- CT Neck: Confirms 2.5 cm mass at tongue base, no thyroid tissue in neck
Diagnosis
Lingual thyroid (ectopic thyroid tissue at the base of tongue) with primary hypothyroidism
Treatment
- Levothyroxine replacement therapy:
- Suppresses TSH
- Reduces size of lingual thyroid through decreased stimulation
- Treats hypothyroidism symptoms
- Monitor with TSH and imaging
- Surgical excision only if:
- Severe obstructive symptoms not responding to suppression
- Bleeding
- Suspected malignancy (rare)
- If surgery required: Lifelong levothyroxine as this may be only thyroid tissue
Clinical Pearl
Lingual thyroid results from failure of the thyroid gland to descend during embryologic development, leaving functioning thyroid tissue at the foramen cecum. It is the most common location for ectopic thyroid tissue. Approximately 70% of patients with lingual thyroid have no other thyroid tissue and will become hypothyroid if the lingual thyroid is removed. This is why thyroid scintigraphy is essential before any surgical intervention - it confirms whether cervical thyroid tissue exists. Most patients can be managed conservatively with thyroid hormone suppression, which reduces TSH-driven growth of the ectopic tissue.
Clinical Image
Endoscopic view showing lingual thyroid as a smooth mass at the base of the tongue posterior to the circumvallate papillae.
Image Source: Wikimedia Commons - "Lingual thyroid" License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Lingual_thyroid.jpg