Lingual Thyroid
Lingual thyroid is a rare developmental condition where thyroid tissue remains at the base of the tongue instead of migrating to its normal position in the neck. This occurs in fewer than 1 in 100,000 people and happens when the thyroid gland fails to complete its normal journey during fetal development. The condition is more common in women than men and may not cause symptoms until hormonal changes occur during puberty, pregnancy, or menopause. Medical imaging is essential for diagnosis and treatment planning.
What is Lingual Thyroid
Lingual thyroid occurs when thyroid tissue fails to move to its proper location during fetal development. Normally, the thyroid gland begins forming at the base of the tongue around the fourth week of pregnancy and then travels down through the neck to settle in its final position below the voice box. When this migration process doesn’t complete properly, thyroid tissue remains at the tongue base, creating what doctors call a lingual thyroid.
This condition is much more common in women than men. Most people with lingual thyroid are born with it, though symptoms may not appear until later in life when hormonal changes occur during puberty, pregnancy, or menopause.
Lingual Thyroid Symptoms and Signs
People with lingual thyroid may experience various symptoms depending on the size and activity of the thyroid tissue. Common symptoms include difficulty swallowing, a feeling of something stuck in the throat, changes in voice quality, and breathing problems. Some individuals may notice a visible mass at the back of their tongue or experience gagging sensations.
Many people with lingual thyroid also develop hypothyroidism, a condition where the body doesn’t produce enough thyroid hormone. This happens because the lingual thyroid tissue may be the only functioning thyroid tissue in the body. Symptoms of hypothyroidism include fatigue, weight gain, cold intolerance, and slow heart rate.
How Lingual Thyroid Appears on Medical Imaging
Medical imaging plays an important role in diagnosing lingual thyroid. Several different imaging techniques can identify this condition, each providing unique information to help doctors make an accurate diagnosis.
CT Scan Findings for Lingual Thyroid
Computed tomography scans show lingual thyroid as a well-defined mass at the base of the tongue. On CT images, the lingual thyroid tissue typically appears denser than surrounding tongue muscle. The mass usually sits in the midline area where the tongue meets the throat. CT scans with contrast enhancement can help distinguish lingual thyroid from other types of masses in this area.
MRI Imaging of Lingual Thyroid
Magnetic resonance imaging provides excellent detail of soft tissues and is particularly useful for evaluating lingual thyroid. On MRI scans, lingual thyroid tissue shows specific signal characteristics that help radiologists identify it. MRI can also help determine the exact size and extent of the lingual thyroid tissue.
Nuclear Medicine Scans for Lingual Thyroid
Thyroid scintigraphy using radioactive iodine or technetium is often the most definitive imaging test for lingual thyroid. This nuclear medicine scan shows whether the tissue at the tongue base is actually functioning thyroid tissue and whether any normal thyroid tissue exists in the neck. In many cases, the lingual thyroid is the only functioning thyroid tissue in the body, making this information important for treatment planning.
Ultrasound Evaluation of Lingual Thyroid
Ultrasound examination of the neck is typically performed to look for normal thyroid tissue in its expected location. In people with lingual thyroid, the neck ultrasound often shows absence of normal thyroid tissue, confirming that the lingual thyroid may be the person’s only source of thyroid hormone production.
Treatment Options for Lingual Thyroid
Treatment for lingual thyroid depends on several factors including the size of the tissue, symptoms experienced, and whether other thyroid tissue exists in the body. Many people with small, asymptomatic lingual thyroid require only regular monitoring with periodic imaging and thyroid function tests.
Medical Management
For people with hypothyroidism due to lingual thyroid, thyroid hormone replacement therapy is the primary treatment. Taking daily thyroid hormone medications can help shrink the lingual thyroid tissue while maintaining normal hormone levels in the body. This approach is often successful for managing symptoms without requiring surgery.
Surgical Treatment
Surgery may be necessary for people with large lingual thyroid causing significant symptoms like difficulty swallowing or breathing problems. However, surgical removal requires careful planning because the lingual thyroid might be the person’s only functioning thyroid tissue. In such cases, doctors must first confirm that normal thyroid tissue exists in the neck or plan for lifelong thyroid hormone replacement after surgery.
Radioactive Iodine Therapy
In some cases, radioactive iodine treatment can help shrink lingual thyroid tissue. This treatment is similar to what is used for overactive thyroid conditions and works by reducing the size and activity of the thyroid tissue at the tongue base.
Long-term Outlook for Lingual Thyroid
The prognosis for people with lingual thyroid is generally excellent with proper management. Many individuals live normal lives with appropriate treatment, whether that involves hormone replacement therapy, surgical intervention, or simple monitoring. Regular follow-up with an endocrinologist helps ensure optimal management of both the lingual thyroid and overall thyroid function.
Conclusion
Lingual thyroid is a rare but manageable condition that occurs when thyroid tissue remains at the base of the tongue instead of moving to its normal neck location during development. Medical imaging, particularly nuclear medicine scans, plays an important role in diagnosing this condition and determining the best treatment approach. While the diagnosis might initially seem concerning, most people with lingual thyroid can be effectively managed with appropriate medical care. If you have been diagnosed with lingual thyroid or suspect you might have this condition, working closely with an endocrinologist and having regular imaging follow-up will help ensure the best possible outcomes for your thyroid health.
References:
- https://pmc.ncbi.nlm.nih.gov/articles/PMC3693310/ – Lingual Thyroid—Conservative Management or Surgery? A Case Report
- https://radiopaedia.org/articles/lingual-thyroid?lang=us – Lingual Thyroid: Radiology Reference Article
- https://tech.snmjournals.org/content/50/4/375 – Thyroid Scintigraphy and SPECT/CT in a Rare Case of Dual Ectopic Thyroid