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Thyroid Guide


Thyroid nodules

Thyroid nodules

General Overview
A thyroid nodule is an unusual growth of cells of the thyroid gland. The thyroid is a small butterfly-shaped gland, which rests in the lower neck. Its main function is to control your body's growth and metabolism. To control metabolism, your thyroid gland produces hormones (thyroxine [T4] and triiodothyronine [T3]). A properly functioning thyroid will produce the right amount of hormones required to keep your body functioning normally. The level of thyroid hormones in the blood is controlled by your pituitary gland.
Studies world over have shown that in 4% to 7% of the population, thyroid nodules can be felt clearly. Prevalence of thyroid nodules is 19% to 67% based on those detected incidentally on ultrasonography. Thyroid nodules usually do not cause any symptoms. Nevertheless their evaluation is considerably important as 5% of all palpable nodules worldwide are found to be cancerous.
Introduction
What is a thyroid nodule?
A thyroid nodule is a growth or a lump, which commonly arises within an otherwise normal thyroid gland. Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland, so they can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can even sometimes be seen as a lump in the front of the neck. They may also be detected during a physical examination conducted by your doctor. Thyroid nodules can be smooth or nodular, soft or hard, spread out or enclosed, movable or fixed, and painful or painless. Majority of the nodules are noncancerous growths. In many cases, the nodules are usually cysts that are filled with fluid. Though most of the thyroid nodules are harmless and would require no treatment, around 5% of them are known to be cancerous. Hence, it is important that you should get your thyroid swelling checked and evaluated by your doctor, so as to rule out a cancerous nodule.
Thyroid nodules are known to occur four times more frequently in woman, though men are at an increased risk of developing a cancerous nodule as compared to women. According to a study conducted in India, solitary thyroid nodules occur eight times more commonly in women, when compared to men. People living in areas with iodine deficiency are more prone to develop thyroid nodules.
There are several types of nodules that can develop in the thyroid gland.
  • Colloid nodule. Majority of the thyroid nodules are colloid nodules that are the most common type and are not associated with an increased risk of becoming malignant (cancerous).
  • Adenoma. This type of thyroid nodule is usually benign (noncancerous).
  • Thyroid cyst. These fluid-filled sacs are usually benign, but certain complex cysts have cystic or solid components due to necrosis or hemorrhage (bleeding) and can sometimes be malignant.
  • Thyroid cancer. These nodules are hard and large causing considerable discomfort and pain. Only 5% of thyroid nodules are cancerous.
  • Miscellaneous. The other types of nodules include inflammatory nodules that develop due to chronic inflammation of the thyroid gland (thyroiditis) and multinodular goiter (condition in which your thyroid gland enlarges forming soft nodules [lumps] within the gland).
Signs and Symptoms
What are the symptoms of a thyroid nodule?
Most often you will not experience any symptoms. The symptoms, if present can include:
  • Discomfort while swallowing.
  • Unable to breathe.
  • Feeling of fullness.
  • Pain and/or pressure exerted on your throat or neck.
  • Presence of a lump on the neck.
  • Change or hoarseness of voice (rarely).
  • Goiter (swelling of the thyroid gland).
If your nodule produces excessive thyroid hormones, it will result in hyperthyroidism (overactive thyroid). The symptoms of overactive thyroid include:
  • Irritability/nervousness.
  • Muscle weakness/tremors.
  • Infrequent, scant menstrual periods.
  • Loss of weight.
  • Increase in appetite.
  • Disturbed sleep.
  • Enlarged thyroid gland.
  • Problems with eye and vision.
  • Heat intolerance.
  • Clammy skin.
You could also develop symptoms of hypothyroidism (underactive thyroid), if you develop thyroid nodules due to Hashimoto's disease (condition in which antibodies are formed against your thyroid tissue). The symptoms of underactive thyroid include:
  • Fatigue.
  • Dryness of skin and hair.
  • Loss of hair.
  • Recurrent and heavy menstrual periods.
  • Facial swelling.
  • Increase in weight.
  • Hoarseness of voice.
  • Cold intolerance.
Causes
What are the causes of thyroid nodule?
Thyroid nodules are formed, when the normal tissues of the gland begin to grow. The exact reason for this is unknown. The most important cause for thyroid nodules is thyroid cancer. But, thyroid cancer is a very rare condition, affecting only 5% of people with thyroid nodules. Thyroid nodules may also be caused by iodine deficiency, suppression of thyroid hormone, and Hashimoto's disease.
Risk Factors
Find out if you are at risk of developing thyroid nodules
Certain factors are known to increase your risk of developing thyroid nodules. They are mentioned below.
  • Family history. Having a parent or sibling with thyroid nodules, thyroid cancer, or other endocrine cancers can increase your risk.
  • Medical history. Radiation therapy to the head and neck area in the past can increase your risk.
  • Age. Though you could develop nodules at any age, your risk increases as you grow older.
  • Gender. Women are at a higher risk of developing thyroid nodules than men.
  • Geography. People living in areas with iodine deficiency are at an increased risk.
Certain factors increase your risk of developing a cancerous nodule, and they are given below.
  • Gender. Men have an increased risk of developing a cancerous nodule, when compared to women.
  • Age. You are at a greater risk of developing cancerous nodules, if you are younger than 20 and older than 70 years.
  • Medical history. A hard nodule or a nodule that is attached to neighboring structures is more likely to be cancerous.
Diagnosis and Screening
How will my doctor diagnose the presence of thyroid nodules?
Thyroid nodules are very often detected, during a routine examination. To evaluate the cause of thyroid nodule, your doctor will record a detailed medical and family history, and perform a physical examination.
Medical and family history:
Your doctor will question you about:
  • Any family history of thyroid disease.
  • The presence of any symptoms that you are having or have experienced.
  • The presence of any risk factors.
Physical examination:
Your doctor will conduct a thorough physical examination, during which he will:
  • Check your thyroid gland for the presence of nodule.
  • Check the adjacent lymph nodes of the head and neck for the presence of pain, tenderness, and swelling.
  • Check the nodule for consistency, size, and texture. Nodules that are soft, smooth, and movable could be benign while those that are hard and fixed could be cancerous.
Do I need testing?
On initial evaluation, if your doctor suspects the presence of a thyroid nodule, he will advise you to undergo certain blood and diagnostic tests.
Blood tests:
Thyroxine (T4) test: Thyroxine is a hormone produced by the thyroid gland. This test is used for measuring the amount of T4 in your blood to determine whether your thyroid is functioning normally. During this test, your blood is collected from a vein, usually from the inside of your elbow or the back of your hand. As some drugs can alter the results, your doctor may advise you to stop them before the test. Your normal T4 levels will range between 4.5 mcg/dL to 11.2 mcg/dL.
Triiodothyronine (T3) test: Triiodothyronine is a hormone produced by the thyroid gland. This test is used for measuring the amount of T3 in your blood to determine, whether your thyroid is functioning normally. During this test, your blood is collected from a vein, usually from the inside of your elbow or the back of your hand. As some drugs can alter the results, your doctor may advise you to stop them before the test. Your normal T3 levels will range between 100 ng/dL to 200 ng/dL.
Thyroid-stimulating hormone (TSH) test: Thyroid-stimulating hormone is a hormone produced by the pituitary gland, which regulates the production and release of the hormones T4 and T3 from the thyroid gland. This blood test is useful for measuring your thyroid function. During this test, your blood is collected from a vein, usually from the inside of your elbow or the back of your hand. As some drugs can alter the results, your doctor may advise you to stop them before the test. Your normal TSH levels will range between 0.4 mIU/L to 4.0 mIU/L. Low TSH level indicates hyperthyroidism, whereas high TSH level is found in hypothyroidism.
Serum calcitonin: Calcitonin is a hormone produced by the thyroid. This test measures the amount of calcitonin in the blood. The exact function of this hormone is not yet known, but your doctor will recommend this test, if you have a family history of medullary thyroid carcinoma. During this test, your blood is collected from a vein, usually from the inside of your elbow or the back of your hand. An elevated level of calcitonin will signify that excessive amount of this hormone is produced.
Diagnostic procedure:
Fine needle biopsy of the thyroid gland: This is a procedure, which involves the removal of cells from the thyroid for examination. During this procedure, a small sample of your thyroid tissue is removed using a fine needle. Though this procedure does not require any special precaution, you should inform your doctor if you have any bleeding disorders, taking any medicines, or if you are pregnant. The site for taking biopsy is determined with the help of an ultrasound device. This sample is later examined under the microscope for detecting any abnormality.
Diagnostic imaging:
Ultrasound of the thyroid: This is an imaging test, which uses high-frequency sound waves to detect any abnormal growth in the thyroid, and small thyroid nodules that cannot be felt during the examination. It helps to differentiate, whether the nodule is solid or fluid-filled cyst. The nodules that are fluid filled are not cancerous and those that are solid might be due to cancer. This imaging procedure is also used during fine needle biopsy of the thyroid to guide the needle.
Thyroid scan: This is an imaging test, which uses radioactive iodine to study how well the thyroid gland is working. During the test, you will be asked to swallow a small quantity of radioactive substance. Sometimes, a small amount of radioactive iodine could also be injected into a vein. This substance travels throughout your blood stream. Your thyroid cells take up this substance and thereby become visible on the scan. Nodules that take up more amount of radioactive iodine than the surrounding thyroid tissue are called 'hot nodules', and they appear darker on the scan. Usually, such nodules are not cancerous. Nodules that take up less amount of radioactive iodine than the surrounding thyroid tissue are called 'cold nodules', and they might be cancerous.
Treatment
What is the treatment of thyroid nodules?
The treatment of thyroid nodules will depend on the type of nodule you have. The various types of treatment will include the following.
No treatment:
As certain thyroid nodules especially noncancerous nodules, disappear without treatment, your doctor would advice no treatment, but would also advice you to undertake regular checkups to monitor the nodule.
Thyroid hormone suppression therapy:
Some doctors treat noncancerous nodules with levothyroxine, which is a synthetic thyroxine pill. This treatment helps to shrink the nodules.
Radioactive iodine:
Your doctor will advise radioactive iodine (I-131) therapy, if you have hyper-functioning thyroid nodules and multinodular goiters. The thyroid gland absorbs the radioactive iodine, and this causes the nodules to shrink. You must not undertake this test, if you are pregnant or planning a pregnancy.
Alcohol ablation:
This is a newer line of treatment. During this treatment, the nodules are injected with ethyl alcohol (ethanol) to shrink the nodules and treat the symptoms of hyperthyroidism.
Surgery:
Removal of the nodules through surgery is the best line of treatment. Your doctor will advice surgery, if the nodules:
  • Are cancerous.
  • Cause symptoms like breathlessness and/or difficulty in swallowing.
  • Are overactive.
  • Cannot be clearly identified as cancerous or non-cancerous.
The surgery will usually involve partial or complete thyroidectomy (removing part or whole of thyroid gland).
Self Care and Lifestyle Change
First of all, remember that the vast majority of thyroid nodules are benign. Next, the nodule should be evaluated by a physician who is comfortable with this problem. Endocrinologists and endocrine surgeons deal with these problems on a regular basis, but many family practice physicians, general internists, and general surgeons are also adept at addressing thyroid nodules.
The cause of thyroid nodules is not known. Thyroid nodules may be caused by iodine deficiency, and hence, enough iodine intake may help to prevent some thyroid nodules. A few useful tips are given below.
  • Consult with a nutritionist on intake of iodine, vitamin, and mineral supplements.
  • Increase your dietary intake of iodine by consuming more iodine rich food like fish, seafood, and sea vegetables.
  • Use iodized salt in your diet, especially if you are living in an endemic area.
You should regularly consult with your doctor to monitor the thyroid nodule and report any new symptoms that you might be experiencing.
References