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- Date Published | June 15, 2017
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- Health Library | Disease & Conditions | Thyroid Disease Description
Thyroid Disease Description
Hyperthyroidism (overactive thyroid)
Hyperthyroidism is due to increased levels of circulating thyroid hormones. The most common cause of hyperthyroidism is Grave's disease, which is an autoimmune disease where the immune system of the body will produce antibodies that will bind to the thyroid cells and stimulate them to make more thyroid hormones. Patients with Grave’s disease usually have a goiter (enlarged thyroid gland) in addition to the other symptoms of hyperthyroidism. In some cases, patients with Grave's disease will have Grave's eye disease, which can present as an inflammation of the eyes or, in severe cases bulging of the eyes. Another cause of hyperthyroidism with goiter is overactive nodular goiter (toxic nodular goiter) which does not have an autoimmune cause. High levels of thyroid hormones will speed up every function in the body. The person with hyperthyroidism will be nervous, irritable, and shaky; there can be racing heart, excessive sweating, heat intolerance, frequent bowel movements, thinning of the hair, weight loss and irregular periods. When there is thyroiditis (inflammation of the thyroid), one can see pain in the neck area, the jaw or the ear together with fever in addition to the symptoms of hyperthyroidism. When hyperthyroidism is suspected, the doctor will measure the blood level of TSH (thyroid stimulating hormone). In this case, the TSH will be low and the doctor will confirm the disorder by measuring blood levels of the thyroid hormones.
To diagnose the cause of the hyperthyroidism, the doctor might need to order a thyroid scan to distinguish between the different causes in order to prescribe the most appropriate thyroid treatments.
Three kinds of treatments are available to help patients with hyperthyroidism and these treatments can be used in combination sometimes: Antithyroid medications (Tapazole or PTU) which can slow the thyroid; radioactive iodine treatments which kill the thyroid cells; and surgical removal of the thyroid gland. The doctor might use a medication called beta-blocker (atenolol, propranolol) which can help with the shakiness and the racing heart). Some cases of Grave's disease can go into remission without the proper thyroid treatments. If radioactive iodine or surgery are used, the person will most likely end up having hypothyroidism and require lifelong thyroid treatments with hormone pills.
Hypothyroidism (underactive thyroid)
Hypothyroidism is due to inability of the thyroid gland to produce enough thyroid hormones. Unlike with Grave’s disease, the thyroid cells in hypothyroidism face autoimmune destruction, which means that the body directs its immune response against these thyroid cells and destroys them; Hashimoto’s disease is another name for this thyroid-cell-destroying process. Other causes of thyroid failure are surgical removal of all or part of the thyroid or its destruction by radiation. Less common causes of thyroid failure are treatments with certain medications or viral infection of the thyroid gland. Lack of iodine in some parts of the world can lead to hypothyroidism. Too much iodine in a susceptible gland can also lead to hypothyroidism.
Symptoms of hypothyroidism include: slowing of the body functions, slower thinking, depression, coldness, constipation, muscle weakness, abnormal periods and slowing of the metabolism leading to moderate weight gain. Some patients will have a goiter (big thyroid gland). It can also cause high cholesterol which in turn can increase the risk of coronary heart disease. A significant proportion of hypothyroid individuals do not have symptoms and this is where screening with a blood test is important. The first thing that the doctor will measure is the blood level of TSH (thyroid stimulating hormone), which will be high in this situation.
No further testing is needed for an obvious case of hypothyroidism (Hashimoto’s disease). A low body temperature does not diagnose hypothyroidism.
Almost all cases of hypothyroidism are irreversible and need to be treated. The treatments consist of replacing the thyroid hormone. Most of the time this is successfully done by using one daily dose of oral levothyroxine (Synthroid, Levoxyl, etc). The doctor will periodically measure the thyroid-stimulating hormone level to guide the treatments.
Goiter (enlarged thyroid)
A goiter simply refers to enlargement of the thyroid gland. Most individuals who have a goiter will not be aware of its presence until it gets to a palpable or visible size. A goiter can get to an enormous size before it causes symptoms of compression, like difficulty breathing or swallowing or change in the voice. Most of the time, a goiter is caused by low iodine supply in the diet. In areas of the world where dietary iodine is low, a large number of patients have goiters. This is a defense mechanism by the thyroid gland to keep up with the needs of the body for thyroid hormones. A goiter may be associated with hyperthyroidism or hypothyroidism; it may contain one or several nodules that can be cancerous in some cases; it is usually painless but its presence can be cosmetically bothersome. The first thing that the doctor will do is order blood tests to make sure the thyroid function is normal. Next, the doctor will determine whether imaging studies are needed such as, ultrasound, CT scan, and etc. Most patients will not require any intervention and will be monitored by periodic neck exam and blood work. If there is suspicion of thyroid cancer or compression symptoms, then surgery to remove all or part of the goiter might be warranted. If the entire thyroid is removed, the patient will require lifelong thyroid hormone medication.
Thyroid nodule refers to a growth in the thyroid gland (link to general description of the thyroid and its disorders). About half the adult population has one or more thyroid nodules. 90 to 95% of these nodules are benign (non-cancerous) and the rest are cancerous. Most thyroid nodules go unrecognized by the patient until they become palpable or visible on exam. When they get to a very big size, they may cause symptoms of compression like difficulty swallowing or breathing or lead to hoarseness. They are usually painless. In rare cases, these nodules may cause hyperthyroidism but most of the time, the thyroid function is not affected by the presence of these nodules. Most nodules are colloid nodules which means that they are similar to normal thyroid tissue but produce more colloid substance which is the normal protein that the thyroid gland manufactures. Some nodules are cysts that contain fluid. At present, it is unclear why nodules form. The most important tool to investigate whether these nodules are benign or cancerous is thyroid biopsy. Thyroid ultrasound is another important imaging modality that helps guide the biopsy and also help monitor the size of the nodules. In some cases, thyroid uptake and scan is performed with radioactive iodine and that might show a cold nodule which means that the nodule is functioning less than normal or a hot nodule which means that the nodule is functioning more than normal. If a nodule is benign, it usually remains benign and does not turn into cancer. If a nodule is confirmed to be benign and if it is not causing hyperthyroidism, then no intervention is needed. If cancer is found, thyroid surgery is recommended. If there is hyperthyroidism, the doctor will discuss with the patient the different potential treatments.
Thyroid cancer is the most common cancer of the endocrine glands. It is most common in individuals with history of exposure of the thyroid gland to radiation, in individuals with family history of thyroid cancer and in those older than 40 years of age. Most thyroid cancers do not give symptoms and they are found as a lump or nodule on examination of the neck or when an imaging test (ultrasound, CT scan, MRI, etc) is done for an unrelated condition. In rare cases, thyroid cancer will cause pain, difficulty swallowing or hoarseness. Cancer is diagnosed on thyroid biopsy or when the thyroid is removed for another cause. The different types of thyroid cancer are papillary cancer which is the most common and the one with the best prognosis; follicular cancer which is next in frequency; medullary cancer which can occur in families; and anaplastic cancer which is typically less likely to respond to treatment. Most of the time, thyroid cancer is confined to the neck. In about 10% of cases, it can spread outside the neck to other organs like the lungs or bones. Mainstay among treatments is total thyroidectomy, which is the complete removal of the thyroid gland. The person will require lifelong treatments with thyroid hormone after the surgery. The doctor will prescribe a relatively high dose of thyroid hormone to suppress TSH, in order to prevent recurrence of the cancer. In papillary and follicular cancers, the doctor will also treat with radioactive iodine (RAI) most of the time. An RAI scan will follow and that will detect any remnant of thyroid tissue whether normal or cancerous and also detect any distant spread of cancer. To be able to treat with RAI and to do the RAI scan, the patient will need to have a high TSH in the blood. To do that, the patient needs to be made hypothyroid by withholding thyroid hormone treatment and allow the TSH to rise in the blood. TSH will stimulate any remaining thyroid tissue to take up iodine. For two weeks preceding the RAI scan and/or treatment, the patient will also observe two weeks of strict low iodine diet. Follow up consists in periodic neck exam, thyroid ultrasound, blood tests for TSH and thyroglobulin.
Thyroiditis refers to an inflammation of the thyroid gland. It can be acute occurring over a few days, subacute occurring over a few weeks or chronic occurring over several months to years. Acute thyroiditis is extremely rare: it is caused by bacteria and its symptoms are high fever and severe pain in the thyroid area. The doctor will prescribe antibiotic treatments sometimes surgery is needed to remove the infected part of the thyroid. Subacute thyroiditis is usually caused by a virus and the symptoms are low grade fever, pain in the jaw and behind the ear. During the acute inflammation, symptoms of hyperthyroidism are seen and may last a few weeks. This is followed by a hypothyroid phase then by a recovery phase. In some patients hypothyroidism will be permanent and require lifelong thyroid hormone treatments. Chronic thyroiditis is caused by an autoimmune process and it is also known as Hashimoto’s thyroiditis. The autoimmune process consists in an activation of the white blood cells which start attacking the thyroid cells. The thyroid gland will try to regenerate new cells to survive the immune attack but will eventually fail; once this happens the person will require lifelong thyroid hormone treatments.
Thyroid eye disease (TED)
This is seen most often in association with Graves’ disease (link to hyperthyroidism). Different symptoms can be seen: redness, itching, excessive tearing, swelling of the eyelids, blurred vision, double vision, corneal ulceration, bulging of the eyes and in its most severe form it can lead to blindness. The process can affect one or both eyes. Significant disease is seen in 10-20% of patients with Grave's disease. Most of the time, the condition improves without treatment. With Grave's disease, thyroid eye disease can happen before, during or after the hyperthyroidism. Typical thyroid eye disease can be seen without any abnormality of thyroid hormone levels. The cause of thyroid eye disease is autoimmune where the white blood cells that are usually responsible for the protection of the body from infections will start producing substances that stimulate the fat behind the eyes or cause swelling of the small muscles that move the eyeballs. This can push the eyeballs forward causing them to bulge out of their sockets. These substances can also cause an inflammation of the eyelids. Most cases of thyroid eye disease do require specific treatments. Inflammation is treated by cold or warm compresses or with eye drops. Severe bulging might require surgical treatment to increase the space inside the eye sockets. Other treatments are investigational and their results are variable.
Thyroid and pregnancy
Each one of the thyroid disorders can occur during pregnancy with a higher frequency than in the general population. The thyroid might enlarge during a normal pregnancy and resume its normal size after delivery. Abnormalities of the thyroid blood tests may be seen during a normal pregnancy and do not necessarily indicate thyroid dysfunction. Differentiating these findings from a true thyroid abnormality might be challenging and require the expertise of a thyroid specialist. Doctors at Cleveland Clinic are familiar with these disorders and with the management of thyroid disease during and after pregnancy. Some medications might be contraindicated during pregnancy or breastfeeding. Any use of radioactive iodine is contraindicated during pregnancy. Post-partum thyroiditis is an inflammation of the thyroid that occurs within a few months of delivery and may be followed by permanent hypothyroidism. Thyroid cancer can occur during pregnancy and might necessitate surgical treatments during the second trimester. Grave's disease usually gets better during pregnancy and may flare up after delivery.
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