What is Ectopic Thyroid?
The thyroid gland, which is involved in regulating the body’s metabolism, is the first endocrine gland (a gland that secretes hormones directly into the blood) to develop in a baby during pregnancy, starting between the third and fourth week. It primarily originates from the endoderm, a layer of cells in an embryo. This forms the majority of each of the side lobes, the bridge connecting these lobes, and several other structures. Some cells that end up in the thyroid originate from two additional formations.
Sometimes, the thyroid doesn’t move to the correct place in the body (which is in front of the windpipe) during development. This is called an “ectopic thyroid.” This misplaced thyroid tissue can end up anywhere from the base of the tongue to a space in the chest called the mediastinum.
The first ectopic thyroid was recorded by a doctor named Hickman, who discovered it in a newborn baby. Unfortunately, the baby passed away after only 16 hours of life due to severe breathing difficulties, which were caused by the ectopic thyroid.
This misplaced thyroid gland falls under a category known as congenital hypothyroidism, which describes the condition where babies are born with an underactive thyroid gland. This condition is one of the main causes of thyroid dysgenesis, which is when the thyroid gland doesn’t form properly during development.
What Causes Ectopic Thyroid?
The development of the thyroid, a gland in your neck that helps regulate your metabolism, involves many elements and is connected to embryological processes or how we develop before birth. Recently, scientific research found that certain genes play an important role in the growth and maturation of the thyroid. These genes are TITF-1(Nkx2-1), Foxe1(TITF-2), and PAX-8. If these genes have any mutations or changes, it could cause the thyroid to not develop correctly.
There are specific genes that can affect where the thyroid grows and its shape as it develops. This is known as ectopic, which means an organ or tissue is in a different place than is typically expected. Also, these genes can influence if the thyroid is smaller than usual, a condition known as thyroid hypoplasia.
For example, the NKX2-5 gene if mutated, can cause the thyroid to develop in an unusual place but does not affect the heart. If the Foxe1 gene is mutated, it can lead to a condition known as Bamforth-Lazarus syndrome where the thyroid gland may be missing or positioned incorrectly.
In thyroid hypoplasia, the NKX2-1 gene, if affected, can cause issues not only with the thyroid but also lead to various body movement disorders and lung abnormalities. Also, the PAX8 gene, if mutated, can cause the thyroid gland to be underdeveloped and may result in hypothyroidism, a condition where the thyroid does not produce enough hormones.
The absence of the thyroid gland, a condition called athyreosis, can also happen if certain mutations occur in genes like FOXE1, NKX2-5, or PAX8.
Risk Factors and Frequency for Ectopic Thyroid
Ectopic thyroid gland, a condition where the thyroid isn’t in its usual place, is quite rare. It happens to only 1 in every 100,000 to 300,000 healthy individuals. However, it’s somewhat more common in individuals with thyroid disease, showing up in about 1 in every 4,000 to 8,000 such patients.
While this condition can show up at any age, it’s often identified in newborns during their initial health screening. Sometimes, the ectopic thyroid isn’t detected until later in life – around the fourth to sixth decade. This typically happens when the ectopic thyroid tissue changes and starts causing symptoms.
In a few situations, the ectopic thyroid gland can enlarge during periods of stress and is then noticed during a scan. It’s important to note that it can affect both men and women equally.
Signs and Symptoms of Ectopic Thyroid
Ectopic lingual thyroid, a condition where the thyroid gland appears at the base of the tongue, often doesn’t show any symptoms. But around half the time, it can cause discomfort or trouble with swallowing, changes in voice, or even obstruct the airway. Sometimes, this condition can also lead to hypothyroidism (an underactive thyroid), causing symptoms like fatigue, sensitivity to cold, constipation, dry skin, weight gain, puffiness in the face, hoarseness, and muscle weakness – this is seen in about 70% of cases. Overactive thyroid or hyperthyroidism, on the other hand, is very rare with this condition. A physical examination of the neck is important to exclude other potential causes of neck lumps. However, it’s worth noting that a regular physical check-up may not always spot ectopic thyroid, meaning it could be missed even by specialist doctors, such as endocrinologists.
Testing for Ectopic Thyroid
For newborn babies, it is recommended to perform a screening for ectopic thyroid, a condition where the thyroid gland is not in its usual location, as there is a high chance they may have low levels of thyroid hormones (a condition known as ‘hypothyroidism’). Thus, certain tests that measure thyroid hormone levels, collectively known as a thyroid profile, are usually done at birth in many health centers.
Specific ongoing tests that help check thyroid function including levels of TSH, T3, total T4, free T4, and a protein called thyroglobulin are crucial in identifying and overseeing the ectopic thyroid status. Most patients with this condition have hypothyroidism, while some may have normal thyroid function, which is referred to as euthyroid.
The specific cause of the ectopic thyroid can be determined using a test called thyroid scintigraphy. This is a specialized imaging process that allows doctors to visualize the thyroid gland and understand how it is functioning. Additionally, MRI and CT scans can also be used to pinpoint the exact location of the ectopic thyroid.
If the patient presents with a lump in the neck, an initial high-resolution ultrasound scan can be beneficial. If the case exhibits strong indications of cancer, a tissue biopsy or a fine-needle aspiration cytology, which are procedures to collect samples for further examination, should be performed.
Treatment Options for Ectopic Thyroid
It is essential to quickly identify congenital hypothyroidism, a condition present from birth that affects the thyroid gland, to prevent potential intellectual disability. The best way to achieve this is to start the right treatment as early as possible and continue it for life. This treatment usually involves taking thyroid hormone replacement therapy and regularly checking in with a doctor.
Sometimes, it might be necessary to surgically remove the thyroid gland if it’s in an abnormal location (a condition known as ectopic thyroid). This could be due to several reasons: it might have become cancerous, there might be bleeding or ulceration, the overactive thyroid condition might be difficult to control, or it could be causing severe local symptoms or difficulties in breathing.
Additionally, some people might have visible thyroid glands in their neck. This is especially common in lingual thyroids, a condition where the thyroid gland is located at the base of the tongue. Such visible thyroid often affects the appearance, causing discomfort, particularly among women. Any individual might choose to undergo surgery for cosmetic reasons in these instances.
What else can Ectopic Thyroid be?
When a doctor is trying to diagnose a condition called ectopic thyroid, there are several other possible conditions they must consider, such as:
- Thyroglossal cyst
- Other types of neck masses
To distinguish a thyroglossal cyst from an ectopic thyroid located on the tongue, doctors can use a procedure called thyroid scintigraphy. Thyroglossal cysts often go undetected in this procedure because they generally don’t have enough functioning thyroid tissue.
Possible Complications When Diagnosed with Ectopic Thyroid
Thankfully, research has shown that the chance of developing cancer from misplaced or ‘ectopic’ tissue is less than 1%. Other rare complications include non-cancerous tumours and thyroid inflammation. If someone with symptoms doesn’t receive treatment, they are more likely to develop complications related to an underactive thyroid, known as hypothyroidism.
Potential Complications:
- Development of cancer from misplaced tissue (less than 1% chance)
- Non-cancerous tumours
- Thyroid inflammation
- Complications from an underactive thyroid if left untreated
