What is a Thyroid Nodule, Why Does It Occur, How Is It Understood and How Is It Treated?
A 48-year-old male patient was admitted due to a swelling that was becoming increasingly apparent in the midline of the neck. In the patient's examination, a lesion compatible with a nodule of approximately 2 cm in diameter was detected on the thyroid gland, close to the midline. It was understood that the mass lesion was more apparent when the patient lifted her head up and back. No specific condition was detected in the patient's other ENT examination.
The result of the patient's thyroid ultrasonography: A palpable, 2.2x1.3 cm isoechoic nodule with a thin regular halo around it, compatible with TI-RADS 1, was observed in the isthmus. No pathological lymphadenopathy was observed in the upper and middle cervical chains of both necks. Neck vascular structures are normal. Soft tissues are normal.
Thyroid nodule definition
A thyroid nodule is a lump that occurs in the thyroid gland due to abnormal growth of cells in your thyroid gland.
The thyroid gland is an endocrine gland that is located in the midline of the neck, under the thyroid cartilage (Adam's apple area) and is shaped like a butterfly. This endocrine gland produces the basic hormones Thyroxine (T4) and Triiodothyronine (T3), which determine our metabolism levels in our body. The hormones secreted by the thyroid gland are effective in determining the working speed of many systems in our body and are effective in the following functions:
- Body metabolic rate (if the level of these hormones increases, the metabolic rate increases and weight loss may occur, (if the level of these hormones decreases, weight gain and metabolism slowdown may occur)
- Body temperature (if the level of these hormones increases, body temperature may increase, if it decreases, body temperature may decrease)
- Mood and excitability
- Pulse and heart rate (if the level of these hormones increases, the pulse rate may accelerate, if it decreases, the pulse rate may decrease)
- Digestion (if the level of these hormones increases, diarrhea may occur, if it decreases, constipation may occur)
Classification of thyroid nodules
Thyroid nodules can be classified roughly according to their number and structure as follows:
- Solitary (if there is a single nodule)
- Multiple (if there is more than one nodule)
- Cystic (if the nodule is filled with fluid)
- Solid (if the nodule is filled with fluid) (if it does not contain)
More than 90% of nodules detected in adults are non-carcinogenic, that is, benign. Sometimes thyroid nodules appear over time due to thyroid disease and may cause the patient to see a doctor as the first symptom. Approximately 5% - 10% of thyroid nodules may present as thyroid cancer. Patients may not see a doctor until these lumps on the thyroid gland become visible and may not be aware of the existence of an existing thyroid disease.
Factors that increase the risk of developing thyroid nodules
Age is generally not a specific risk factor, thyroid nodules can occur in anyone, including children and adults. The risk of developing thyroid nodules may increase with age. Thyroid nodules are less common in children.
The risk of developing thyroid nodules is higher in women as a gender. In general, thyroid nodules can be seen 4 times more in women.
A diet low in iodine can also increase the risk of developing thyroid nodules. Since iodine is necessary for your thyroid gland to produce hormones, using iodized salt and consuming other iodine sources may be beneficial.
Other factors that increase the risk of thyroid nodules are:
- History of thyroid radiation (can cause the development of acneserogeneous thyroid lesions such as papillary thyroid cancer).
- Having a family history of thyroid nodules or thyroid cancer (predisposition to the development of thyroid nodules)
- Iron deficiency anemia.
- Smoking (smoking may facilitate the development of both carcinogenic and non-carcinogenic mass lesions in the thyroid gland)
- Obesity
- Metabolic syndrome
- Alcohol use
- Increased levels of insulin-like growth factor-1 (IGF-1).
- Uterine fibroids
Frequency of Thyroid Nodules
Because thyroid nodules are found in asymptomatic people, it may not be easy to understand their true frequency. Approximately 5% to 7% of adults who go to hospital have a thyroid nodule. Ultrasound imaging shows that 20% to 76% of adults have thyroid nodules. This means that many patients with thyroid nodules are actually unaware of their condition.
When should I worry about thyroid nodules?
In most cases, there is no need to worry about thyroid nodules. Since some thyroid nodules can be cancerous, it would be best to see a doctor and rule out carcinogenic lesions. While examination of thyroid nodules, USG examinations and, if necessary, blood tests provide rough information about the nodules in the first examination, USG-guided FNAB can be planned in suspicious cases.
The increase in the diagnosis of thyroid lesions, in part due to advances in imaging technology and increased use of imaging, leads to higher thyroid nodule detection rates. Accordingly, the thyroid cancer incidence rate and thyroidectomy rate have increased.
When performed by an experienced team, fine needle aspiration (FNA) biopsies and, accordingly, a higher incidence of subclinical thyroid cancer are detected. FNA is the most important minimally invasive diagnostic tool used in the evaluation of thyroid nodules. In 20-25% of thyroid lesions, carcinogenic and morphological distinctions cannot be easily made. Various algorithms have been developed to avoid unnecessary surgical procedures in these patients.
According to the American Thyroid Association (ATA), ultrasonography (US) is the first-line imaging method of choice for thyroid nodule evaluation (source >> https://pubmed.ncbi.nlm.nih.gov/26462967/). Accurate US evaluation of thyroid lesions can help reduce unnecessary inclusion of benign nodules in FNA procedures and unnecessary examinations. In addition to physicians benefiting from this easily accessible imaging tool; several thyroid nodule risk classification systems based on US features have been published. In 2009, Horvath et al. proposed a Thyroid Imaging, Reporting, and Data System (TIRADS) that was accepted by the American College of Radiology (ACR) and later recommended and based on the distribution of US features into five categories (composition, echogenicity, shape, margins, and echogenic foci) (source >> https://pubmed.ncbi.nlm.nih.gov/19276237/). Link where you can see the ACR Thyroid Imaging Reporting and Data System (ACR TI-RADS) scoring system >> ACR Thyroid Imaging Reporting and Data System (ACR TI-RADS) | Radiology Reference Article | Radiopaedia.org
Changes in the structure of thyroid nodules (intranodular hemorrhage and other changes) due to previous FNAB may cause a previously aspirated thyroid nodule to be incorrectly classified as TIRADS 4a (source >> https://pmc.ncbi.nlm.nih.gov/articles/PMC6463999/). In order for this classification to be accurate and suitable for international use, radiologists performing US imaging must be trained and experienced. US examination depends on the experience and knowledge of the person performing the procedure.
Thyroid Nodule Symptoms
Most thyroid nodules do not cause any symptoms. They are usually noticed by patients as they increase in size and become noticeable from the outside. Sometimes, they are noticed by the doctor who consults them due to the symptoms of the thyroid disease that caused the nodule. When thyroid nodules become very large, they can cause the following symptoms:
- Pain in the front or middle of the neck
- Swallowing problems (may occur if the nodule is very large)
- Hoarseness or voice changes
- Enlargement of the thyroid gland (goiter)
Thyroid nodules can cause overactive thyroid hormone production, which can lead to increased levels of thyroid hormones, also known as "hyperthyroidism," and can cause additional symptoms, including:
- A rapid heart rate and palpitations
- Increased appetite
- Weight loss
- Increased diarrhea and bowel activity
- Shaking and/or feeling jittery
- Difficulty sleeping
- Light or skipped menstrual periods
In contrast to the above, thyroid nodules can also be associated with low thyroid hormone levels (hypothyroidism). This condition is called "Hypothyroidism" and the following additional symptoms may occur:
- Fatigue, weakness
- Numbness and tingling in the hands
- Dry, hard skin and hair
- Constipation, decreased bowel activity
- Depression
- Frequent, heavy menstrual periods
- Weight gain
What Causes Thyroid Nodules and What Are Their Types?
It is not always easy to understand why thyroid nodules form and why they occur. In most cases, the underlying cause cannot be easily found. Thyroid nodules can occur due to various reasons and there are nodules with different structures. Below you can find the types of thyroid nodules:
Inflammatory nodules: These nodules can occur as a result of chronic inflammation or inflammation of your thyroid gland. Some are due to an autoimmune disease and in most cases, pain in the midline of the neck can be experienced in these inflammatory thyroid diseases. Even when the nodules are small, US imaging and early diagnosis can be provided by causing patients to see a doctor.
Colloid nodules: The most common cases are thyroid nodules. They are abnormal growths of thyroid tissue. These nodules are not cancerous and do not spread outside the thyroid gland.
Thyroid cysts (cystic thyroid nodules): They are nodules with fluid inside. The structure of these nodules can be a mixture of solid and liquid. Some cystic nodules can be cancerous and have a low cancer risk. The size of cystic thyroid nodules is very important. Biopsy may be recommended for those that reach a size larger than 2 cm. Ultrasound follow-up of small cystic nodules is important. Sometimes, when there is bleeding inside solid nodules or when FNAB is performed, a liquid structure can be revealed inside them and can be reported as a cystic nodule in the next near-term ultrasound imaging.
Multinodular goiter: Goiter is a word used for the enlargement of the thyroid gland. Multinodular goiter, as its name suggests, is also used to mean that the thyroid is large with many nodules. The nodules here are usually benign. When viewed from the outside, they may cause patients to be anxious as they will give symptoms as a mass lesion in the middle or even distinct in the neck.
Hyperfunctional thyroid nodules: These are nodules that produce thyroid hormone. Hyperthyroidism and related symptoms such as sweating, palpitations, weight loss, and restlessness may be observed due to excessive production of thyroid hormone, and medical treatment may be required. Over time, it may cause the patient's eyes to grow outward. When caught early, when thyroid hormone levels return to normal (euthyroidism), the thyroid tissue can be removed with surgery.
Thyroid cancer (carcinogenic nodules): The thyroid nodule that causes the greatest concern and scares patients the most is that it is carcinogenic. Generally, less than 6.5% of all thyroid nodules are cancerous. During US follow-up, if there is a sudden change in the size and structure of the patient's thyroid nodules, or abnormal growths in neighboring lymph nodes, urgent FNAB may be required, and in this case, there is a possibility that it is a cancerous thyroid nodule. Unlike inflammatory nodules, they do not cause pain or any other symptoms in the early stage. When they grow too large, they can be noticed as a mass in the neck or can spread to the surrounding tissue and cause other symptoms.
Thyroid Nodule Diagnosis and Necessary Tests
Thyroid nodules are sometimes detected incidentally!
Sometimes patients may notice nodules in the thyroid gland when they see a doctor, during a doctor's examination, or on their own. Sometimes, when there are no complaints or symptoms, they may be detected by chance on an imaging tool (such as USG or MRI) that is requested and applied to the neck area. A patient of mine had been treated for a long time with the diagnosis of chronic pharyngitis for the pain he described as a sore throat and was in the midline of the neck and slightly below. The patient had been given many different medications, including throat gargles and painkillers, at different clinics, and when I asked about the localization of the pain during the examination, the patient directly pointed to the thyroid gland, so I examined it manually. After noticing the tenderness in the thyroid gland, the US imaging I requested revealed that it was inflammatory thyroiditis and small thyroid nodules. I asked the patient to consult an endocrinologist. There are many patients with thyroid nodules and thyroid gland diseases who have not been diagnosed or have been misdiagnosed, like the patient I shared with you here.
Although thyroid nodules are usually not cancerous; when a thyroid nodule is diagnosed, the patient needs to be evaluated in detail to exclude carcinogenic nodules and, if necessary, to determine the outcome.
Tests and examinations that may be required for the evaluation of thyroid nodules after examination
The following tests and examinations may be useful in cases of suspected thyroid nodule or when a thyroid nodule is detected, when a thyroid gland disease is initially diagnosed:
Thyroid hormone test: Although this blood test is not distinctive in many thyroid nodules, since some thyroid nodules cause active hormone production, changes in thyroid hormone levels in the blood may be detected.
Tests for inflammatory thyroid diseases: Antibodies produced against the thyroid gland and general infection markers may be requested in blood tests.
Thyroid ultrasound: This is perhaps the most useful and non-invasive diagnostic tool in the evaluation of thyroid nodules. The fact that the physician performing the thyroid USG is highly experienced and knowledgeable is very important in the differential diagnosis of nodules and in the follow-up of the patient. It is also very important in determining whether FNAB is necessary in patients. Sound waves are used in US imaging and it does not cause a carcinogenic effect like radiation. Thyroid USG evaluates whether the nodule is solid or fluid-filled, whether there are any changes in the nodule structure and size during follow-up, whether the thyroid tissue is normal, and the structure of the lymph nodes around the thyroid gland. The scoring system mentioned above can provide clinicians with information about the risk status of the nodule. Sometimes, the blood supply pattern of the nodule can be provided to clinicians simultaneously with Doppler USG. Considering these, when FNAB is required, US can be used as a guide for the physician performing the thyroid FNAB to properly place the needle.
Thyroid FNAB: In this examination, an aspiration needle is inserted into the thyroid gland and the nodule. Aspiration is performed with a syringe to obtain a sample. The sample is spread on a slide and coverslip and sent to the laboratory for evaluation. There are several factors that limit the reliability of this examination. Although it is advantageous to be minimally invasive; only aspiration is performed from a certain area of the nodule during FNAB. Performing it under US guidance ensures that the correct thyroid nodule is reached and the needle is inserted correctly. During thyroid FNAB, when only fluid or blood is aspirated in nodules containing fluid, a sufficient number of diagnostic cells may not be reached. Therefore, it is important to perform FNAB under US guidance and have a cytopathologist examine the aspiration content under a microscope at the same time to provide information on whether the material is sufficient. Thyroid FNAB results do not have as definitive a diagnostic value as an excisional biopsy. It may need to be repeated in suspicious nodules.
The radioactive iodine uptake test (RAIU): In this test, radioactive iodine is administered orally to patients. The aim here is to compare how much radioactive iodine is absorbed by thyroid nodules and normal thyroid tissue and their absorption rates. The radioactive substances commonly used during thyroid uptake tests are I-131, technetium-99m pertechnetate or iodine-123. According to the degree of RAI absorption, thyroid nodules can be classified as "hyperactive nodule" or "hot nodule", "hypoactive nodule" or "cold nodule". 85% of nodules are cold nodules and the risk of cold nodules being cancerous is 15% (source >> https://pubmed.ncbi.nlm.nih.gov/7503088/). As has long been known, the risk of cancer in hot nodules is really rare. Many guidelines state that FNA is not necessary in hot nodules in the first place. However, a recent literature review found that 3.1% of surgically removed hyperfunctioning thyroid nodules were malignant, and most of these were follicular or Hürthle cell cancers. In other words, hot thyroid nodules may also have carcinogenic properties (source >> https://thyroidresearchjournal.biomedcentral.com/articles/10.1186/1756-6614-6-7).
How is Follow-up and Treatment in Thyroid Nodules?
Treatment of thyroid nodules can be planned according to the type of thyroid nodule, the underlying cause and whether there is a carcinogenic risk.
Only follow-up of the patient: In nodules with a low risk of cancer, patients can only be checked by a doctor at certain times. Sometimes patients may have thyroid US and various blood tests and compare them with the tests in previous check-ups. If there is no change in the size and structure of the thyroid nodules and there is no variability in the blood tests, the patient's follow-up continues.
Radioactive iodine treatment: Especially in the presence of hyperfunctional, i.e. hormone-producing nodules, if patients have symptoms of hyperthyroidism, radioactive iodine treatment can be planned for the treatment of these nodules. In this treatment, the thyroid gland and nodules absorb radioactive iodine (the most active ones absorb the most). In this way, the nodules shrink.
Surgical treatment: In cancerous thyroid nodules, in nodules that change structure and grow during follow-up, in nodules with suspicious content and in which atypical cells or cancerous cells are detected in FNAB, in nodules that grow suddenly or cause swallowing or respiratory problems in patients, the thyroid gland can be resected completely or nearly completely. In patients with hyperthyroidism, it is ideal to plan the operation after the hormone levels return to normal.
Can Thyroid Nodules Be Prevented?
Since the cause of most thyroid nodules is unknown, it is often not possible to prevent them. However, measures against factors that increase the risk of developing thyroid nodules may be useful, including:
- Preventing obesity, losing weight and exercising regularly
- Quitting smoking
- Using iodized table salt
- Avoiding goitrogenic foods (although there is no definite relationship, it is beneficial not to consume these foods as they can affect the metabolism of the thyroid gland). Again, avoiding goitrogenic medications may be beneficial. You can find them at the link >> https://kresserinstitute.com/goitrogenic-foods-and-thyroid-health/
- Avoiding unnecessary radiation exposure to the thyroid gland (avoiding unnecessary X-rays and tomography, which cause radiation)
Apart from these, oral birth control pills and statins used to lower cholesterol may reduce the risk of developing thyroid nodules.
Prognosis for Thyroid Nodules
Most thyroid nodules are not cancerous, and the prognosis for these patients is excellent or they simply have to live with the nodules. These patients usually do not need treatment.
The prognosis for cancerous (malignant) thyroid nodules depends on the type of cancer in the nodule, the patient's age and other characteristics at the time of diagnosis, whether it has spread to nearby lymph nodes, whether the tumor has metastasized to distant areas, and whether the tumor has spread to the local area. Early detection and treatment of cancerous nodules is important.
Children Have a Higher Risk of Cancer in Thyroid Nodules!
Thyroid nodules are much less common in children than in adults. The frequency here is not clear. Unfortunately, thyroid nodules in children are more often cancerous. Together, this rate can be around 25%. In other words, the remaining 75% are again non-cancerous thyroid nodules.
Murat Enoz, MD, Otorhinolaryngology, Head and Neck Surgeon
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