What is a Thyroid Nodule?
The thyroid gland is one of the largest endocrine glands and is situated at the base of the neck, above the sternum (breastbone). It is shaped like a butterfly and its function is to produce hormones, which regulate the body's metabolism and other important functions.
Thyroid nodule, as the name itself indicates, are nodes or lumps filled with fluid or solid, which develop inside the thyroid gland. Most of the thyroid nodules are not a cause of concern and often do not produce symptoms in the patient. Only a minor percentage of thyroid nodules can indicate or turn into thyroid cancer. Thyroid nodule often goes unnoticed by the patient and is usually discovered during a regular medical exam. In some cases, the thyroid nodules increase sufficiently in size that they become visible or cause problems for the patients, such as difficulty in breathing or swallowing.
Treatment of thyroid nodule depends on the type of the nodule the patient has in his/her thyroid gland.
Causes of Thyroid Nodule
Given below are various conditions which cause development of thyroid nodules:
- Deficiency of iodine in the diet can also lead to development of thyroid nodules.
- Thyroid cyst, which is the formation of fluid-filled cavities in the thyroid gland, is commonly caused by degeneration of thyroid adenomas. There is a combination of solid components with fluid in the thyroid cysts. These are usually benign in nature; however, in some cases they can have solid components which are malignant.
- Overgrowth of normal thyroid tissue can also cause thyroid nodules. The exact reason for this is not clear. Such type of growth of the thyroid tissue is also known as thyroid adenoma. It is noncancerous or benign in nature and is only a cause of concern if it causes symptoms due to its size.
- Goiter is a term used to describe any type of thyroid gland occurring as a result of thyroid disorder or iodine deficiency. A multinodular goiter is a condition where there is formation of multiple nodules within the goiter. The cause of this is not clear.
- Thyroiditis is a condition where there is chronic inflammation of the thyroid gland. Thyroid disorders, such as Hashimoto's disease, may cause inflammation in the thyroid gland leading to development of thyroid nodules and their enlargement in the thyroid gland. This commonly occurs with hypothyroidism.
- Thyroid cancer can also cause thyroid nodules, although the risk for the nodule being malignant is very minor. However, certain factors increase the risk of it being a thyroid cancer and this includes: family history of thyroid cancer or other endocrine cancers, if the patient is lesser than age of 30 or older than 60 years, is a male, or has a previous history of radiation exposure, especially to the neck and head. A thyroid nodule, which is hard or large in size, causes discomfort or pain should be a cause of concern for malignancy.
Complications of Thyroid Nodule
- Hyperthyroidism is a complication of a thyroid nodule, which occurs when the nodule or the goiter starts producing thyroid hormone, causing hyperthyroidism. This condition can lead to weight loss, heat intolerance, muscle weakness, and irritability or anxiousness. Other complications of hyperthyroidism are irregular heartbeat, osteoporosis (weak bones); and thyrotoxicosis.
- Difficulty in breathing or swallowing can occur if the thyroid nodule(s) is of a bigger size or if there is a multinodular goiter where there is thyroid gland enlargement with presence of multiple distinct nodules which interfere with breathing or swallowing.
- Complications resulting from thyroid cancer. In cases where thyroid nodule is cancerous, then surgery needs to be done where the majority of the thyroid gland or the entire thyroid gland is removed. After the surgery, patient needs to take thyroid hormone replacement therapy for his/her remaining life.
Signs & Symptoms of Thyroid Nodule
Patients commonly do not experience signs or symptoms from thyroid nodules. In some cases where the thyroid nodules become large they cause symptoms such as:
- The thyroid nodules can be felt.
- The thyroid nodules are visible and are seen as a swelling at the base of the neck.
- The enlarged thyroid nodules compress the esophagus or windpipe causing problems, such as difficulty in swallowing or shortness of breath.
In some patients, the thyroid nodules start producing extra thyroxine, which is a hormone normally secreted by the thyroid gland. The patient experiences symptoms of hyperthyroidism due to the production of the excessive thyroxine, such as:
- Heat intolerance.
- Unexplained weight loss.
- Irregular or rapid heartbeat.
Serious Symptoms of Thyroid Nodule
Some thyroid nodules can be malignant (cancerous), so it is important to determine if the thyroid nodules are malignant. However, this can't be done based on the patient's symptoms alone. Majority of the cancerous thyroid nodules have slow growth and may be small in size when they are detected. It is rare to find aggressive thyroid cancers where the cancerous thyroid nodules are large in size, fixed, firm and fast growing.
As mentioned before, most of the thyroid nodules are benign or noncancerous and usually are not a cause for concern. However, the patient needs to seek immediate medical attention if he/she is having problems with swallowing or breathing. Medical attention should also be sought if the patient experiences signs and symptoms of hyperthyroidism, which include:
- Rapid heartbeat.
- Sudden and unintentional weight loss even when the appetite of the patient is normal.
- Difficulty in sleeping.
- Weakness in the muscles.
- Irritability or nervousness.
Diagnosis of Thyroid Nodule
It is important to exclude if the thyroid nodule is cancerous however, there is less chances of it being cancerous. The doctor will examine the nodule or lump in the neck and will find out if the function of the thyroid gland is normal by conducting the following investigations:
- Physical exam is done where the patient is asked to swallow while the doctor examines the thyroid gland to look if the thyroid gland nodule is moving up and down upon swallowing.
- Thyroid function tests are done, which measure the thyroxine and triiodothyronine levels in the blood. These hormones are produced by the thyroid gland. The thyroid-stimulating hormone or TSH is produced by the pituitary gland and helps in finding out if the thyroid gland is producing excessive thyroxine as in case of hyperthyroidism or producing very less thyroxine, which will indicate hypothyroidism.
- Ultrasonography is an imaging technique which uses sound waves of high-frequency to generate images. This test helps in giving information about the structure and shape of the thyroid nodules and also helps in differentiating cysts from solid nodules, in determining if there are multiple nodules present. Ultrasound also helps in guidance when doing a fine-needle aspiration biopsy.
- Fine-needle aspiration (FNA) biopsy is done from the thyroid nodules to exclude cancer. FNA biopsy also helps in differentiating between malignant and benign thyroid nodules. In this procedure, a very thin needle is inserted in the nodule and a sample of cells from the thyroid nodule is taken. FNA takes about 25 minutes to be done and carries very less risk. Ultrasound is used for guiding the placement of the needle. The tissue cell samples are sent to the laboratory where they are analyzed under a microscope.
- Thyroid scan helps in evaluating the thyroid nodules. During this test, an isotope of radioactive iodine is injected into the vein of the arm. This helps in delineating the images clearly. A camera then generates images of the thyroid gland and the nodules on a computer screen. Thyroid nodules which produce extra thyroid hormone are known as hot nodules and show up clearly on the thyroid scan, as they absorb more of the isotope when compared to a normal thyroid tissue. Cold nodules appear as holes or defects in the scan and are nonfunctioning. Most of the hot nodules are noncancerous; however, some of the cold nodules can be cancerous or malignant. The thyroid scan, however, can't distinguish between malignant and benign cold nodules. The duration of the thyroid scan depends on the time it takes the isotope to reach the thyroid gland. Patient may experience some discomfort in the neck, as the neck is stretched backwards when the thyroid scan is done. There is also some exposure to radiation.
Treatment of Thyroid Nodule
Treatment for Thyroid Nodule depends on the type of thyroid nodule the patient has and includes:
Treatment for Benign Thyroid Nodules
- Observing and watchful waiting is done if the biopsy reveals that the thyroid nodule is benign. This includes having regular physical exam and thyroid function tests. If the thyroid nodule increases in size, then another biopsy will be done. If there is no change in the benign thyroid nodule, then treatment is not required.
- Thyroid hormone suppression therapy can be done for a benign thyroid nodule using levothyroxine, which is a synthetic form of thyroxine taken in a pill form. This is done so that excessive thyroid hormone will make the pituitary gland to produce lesser thyroid stimulating hormone (TSH). This type of treatment with levothyroxine therapy is still under research, as there is no clear evidence that this treatment will continuously shrink the thyroid nodules or if shrinking the benign and small thyroid nodules is even needed.
- Surgery is needed if a benign thyroid nodule increases in size and causes breathing or swallowing difficulties. Surgery is also done for patients having large multinodular goiters, especially if the goiters are compressing the airways, blood vessels or esophagus. Surgery may also be done for those thyroid nodules, which have been diagnosed as suspicious or indeterminate by a biopsy and examined for any signs of malignancy or cancer.
Treatment for Thyroid Nodules which Cause Hyperthyroidism
If there is excessive production of thyroid hormones from the thyroid nodule then treatment for hyperthyroidism is started, which includes:
- Anti-thyroid medications, such as methimazole are prescribed to help in reducing the symptoms of hyperthyroidism. Treatment is usually long-term and includes serious side effects on the liver.
- Radioactive iodine is used for treating multinodular goiters or hyperfunctioning adenomas. Radioactive iodine can be taken in a liquid form or a capsule form and is absorbed by the thyroid gland, which causes shrinking of the thyroid nodules and decreasing and resolution of the signs and symptoms of hyperthyroidism in about a couple of months.
- Surgery is done if the above treatment methods do not work or if the above treatments are not an option for the patient. The risks of the surgery should be thoroughly discussed with the doctor.
Treatment for Cancerous Thyroid Nodules
Again surgery is required for treating cancerous thyroid nodules where the thyroid gland with the malignant nodules is surgically removed. The majority of thyroid tissue can be removed and this procedure is known as near-total thyroidectomy. The risks of this surgery comprises of damage to the laryngeal nerve, which controls the vocal cords and damage to the parathyroid glands, which help in controlling the calcium level in the blood. Patient needs lifelong treatment of levothyroxine after thyroidectomy is done in order to supply the body with the normal amounts of thyroid hormone.