Thyroid disease

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Thyroid disease
Blausen 0534 Goiter.png
An illustration of goiter, a type of thyroid disease
Specialty Endocrinology, medical genetics   OOjs UI icon edit-ltr-progressive.svg

Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones [1] that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ. These hormones normally act in the body to regulate energy use, infant development, and childhood development. [2]

Contents

There are five general types of thyroid disease, each with their own symptoms. A person may have one or several different types at the same time. The five groups are:

  1. Hypothyroidism (low function) caused by not having enough free thyroid hormones [2]
  2. Hyperthyroidism (high function) caused by having too many free thyroid hormones [2]
  3. Structural abnormalities, most commonly a goiter (enlargement of the thyroid gland) [2]
  4. Tumors which can be benign (not cancerous) or cancerous [2]
  5. Abnormal thyroid function tests without any clinical symptoms (subclinical hypothyroidism or subclinical hyperthyroidism). [2]

In the US, hypothyroidism and hyperthyroidism were respectively found in 4.6 and 1.3% of the >12y old population (2002). [3]

In some types, such as subacute thyroiditis or postpartum thyroiditis, symptoms may go away after a few months and laboratory tests may return to normal. [4] However most types of thyroid disease do not resolve on their own. Common hypothyroid symptoms include fatigue, low energy, weight gain, inability to tolerate the cold, slow heart rate, dry skin and constipation. [5] Common hyperthyroid symptoms include irritability, anxiety, weight loss, fast heartbeat, inability to tolerate the heat, diarrhea, and enlargement of the thyroid. [6] Structural abnormalities may not produce symptoms, however some people may have hyperthyroid or hypothyroid symptoms related to the structural abnormality or notice swelling of the neck. [7] Rarely goiters can cause compression of the airway, compression of the vessels in the neck, or difficulty swallowing. [7] Tumors, often called thyroid nodules, can also have many different symptoms ranging from hyperthyroidism to hypothyroidism to swelling in the neck and compression of the structures in the neck. [7]

Diagnosis starts with a history and physical examination. Screening for thyroid disease in patients without symptoms is a debated topic although commonly practiced in the United States. [8] If dysfunction of the thyroid is suspected, laboratory tests can help support or rule out thyroid disease. Initial blood tests often include thyroid-stimulating hormone (TSH) and free thyroxine (T4). [9] Total and free triiodothyronine (T3) levels are less commonly used. [9] If autoimmune disease of the thyroid is suspected, blood tests looking for Anti-thyroid autoantibodies can also be obtained. Procedures such as ultrasound, biopsy and a radioiodine scanning and uptake study may also be used to help with the diagnosis, particularly if a nodule is suspected. [2]


Thyroid diseases are highly prevalent worldwide, [10] [11] [12] and treatment varies based on the disorder. Levothyroxine is the mainstay of treatment for people with hypothyroidism, [13] while people with hyperthyroidism caused by Graves' disease can be managed with iodine therapy, antithyroid medication, or surgical removal of the thyroid gland. [14] Thyroid surgery may also be performed to remove a thyroid nodule or to reduce the size of a goiter if it obstructs nearby structures or for cosmetic reasons. [14]

Signs and symptoms

Symptoms of the condition vary with type: hypo- vs. hyperthyroidism, which are further described below.

Possible symptoms of hypothyroidism are: [15] [16]

Possible symptoms of hyperthyroidism are: [17]

Note: certain symptoms and physical changes can be seen in both hypothyroidism and hyperthyroidism —fatigue, fine / thinning hair, menstrual cycle irregularities, muscle weakness / aches (myalgia), and different forms of myxedema. [18] [19]

Diseases

Low function

Hypothyroidism is a state in which the body is not producing enough thyroid hormones, or is not able to respond to / utilize existing thyroid hormones properly. The main categories are:

High function

Exophthalmos is the eye bulging that may be seen with Graves Disease, one of the major causes of hyperthyroidism OSC Microbio 19 02 exophth.jpg
Exophthalmos is the eye bulging that may be seen with Graves Disease, one of the major causes of hyperthyroidism

Hyperthyroidism is a state in which the body is producing too much thyroid hormone. The main hyperthyroid conditions are:

Structural abnormalities

Endemic goiter Kone med stor struma.jpg
Endemic goiter

Tumors

Medication side effects

Certain medications can have the unintended side effect of affecting thyroid function. While some medications can lead to significant hypothyroidism or hyperthyroidism and those at risk will need to be carefully monitored, some medications may affect thyroid hormone lab tests without causing any symptoms or clinical changes, and may not require treatment.[ citation needed ] The following medications have been linked to various forms of thyroid disease:

Pathophysiology

Most thyroid disease in the United States stems from a condition where the body's immune system attacks itself. In other instances, thyroid disease comes from the body trying to adapt to environmental conditions like iodine deficiency or to new physiologic conditions like pregnancy.

Autoimmune Thyroid Disease

Autoimmune thyroid disease is a general category of disease that occurs due to the immune system targeting its own body. It is not fully understood why this occurs, but it is thought to be partially genetic as these diseases tend to run in families. [9] In one of the most common types, Graves' Disease, the body produces antibodies against the TSH receptor on thyroid cells. [4] This causes the receptor to activate even without TSH being present and causes the thyroid to produce and release excess thyroid hormone (hyperthyroidism). [4] Another common form of autoimmune thyroid disease is Hashimoto's thyroiditis where the body produces antibodies against different normal components of the thyroid gland, most commonly thyroglobulin, thyroid peroxidase, and the TSH receptor. [9] These antibodies cause the immune system to attack the thyroid cells and cause inflammation (lymphocytic infiltration) and destruction (fibrosis) of the gland. [9]

Goiter

Goiter is the general enlargement of the thyroid that can be associated with many thyroid diseases. The main reason this happens is because of increased signaling to the thyroid by way of TSH receptors to try to make it produce more thyroid hormone. [9] This causes increased vascularity and increase in size (hypertrophy) of the gland. [9] In hypothyroid states or iodine deficiency, the body recognizes that it is not producing enough thyroid hormone and starts to produce more TSH to help stimulate the thyroid to produce more thyroid hormone. [9] This stimulation causes the gland to increase in size to increase production of thyroid hormone. In hyperthyroidism caused by Graves' Disease or toxic multinodular goiter, there is excess stimulation of the TSH receptor even when thyroid hormone levels are normal. [4] In Graves' Disease this is because of an autoantibodies (Thyroid Stimulating Immunoglobulins) which bind to and activate the TSH receptors in place of TSH while in toxic multinodular goiter this is often because of a mutation in the TSH receptor that causes it to activate without receiving a signal from TSH. [4] In more rare cases, the thyroid may become enlarged because it becomes filled with thyroid hormone or thyroid hormone precursors that it is unable to release or because of congential abnormalities or because of increased intake of iodine from supplementation or medication. [9]

Pregnancy

There are many changes to the body during pregnancy. One of the major changes to help with the development of the fetus is the production of human chorionic gonadotropin (hCG). This hormone, produced by the placenta, has similar structure to TSH and can bind to the maternal TSH receptor to produce thyroid hormone. [23] During pregnancy, there is also an increase in estrogen which causes the mother to produce more thyroxine binding globulin, which is what carries most of the thyroid hormone in the blood. [24] These normal hormonal changes often make pregnancy look like a hyperthyroid state but may be within the normal range for pregnancy, so it necessary to use trimester specific ranges for TSH and free T4. [23] [24] True hyperthyroidism in pregnancy is most often caused by an autoimmune mechanism from Graves' Disease. [23] New diagnosis of hypothyroidism in pregnancy is rare because hypothyroidism often makes it difficult to become pregnant in the first place. [23] When hypothyroidism is seen in pregnancy, it is often because an individual already has hypothyroidism and needs to increase their levothyroxine dose to account for the increased thyroxine binding globulin present in pregnancy. [23]

Diagnosis

Diagnosis of thyroid disease depends on symptoms and whether or not a thyroid nodule is present. Most patients will receive a blood test. Others might need an ultrasound, biopsy or a radioiodine scanning and uptake study.

Blood tests

Overview of the thyroid system and the various hormones involved. Thyroid system.svg
Overview of the thyroid system and the various hormones involved.

Thyroid function tests

There are several hormones that can be measured in the blood to determine how the thyroid gland is functioning. These include the thyroid hormones triiodothyronine (T3) and its precursor thyroxine (T4), which are produced by the thyroid gland. Thyroid-stimulating hormone (TSH) is another important hormone that is secreted by the anterior pituitary cells in the brain. Its primary function is to increase the production of T3 and T4 by the thyroid gland.

The most useful marker of thyroid gland function is serum thyroid-stimulating hormone (TSH) levels. TSH levels are determined by a classic negative feedback system in which high levels of T3 and T4 suppress the production of TSH, and low levels of T3 and T4 increase the production of TSH. TSH levels are thus often used by doctors as a screening test, where the first approach is to determine whether TSH is elevated, suppressed, or normal. [25]

  • Elevated TSH levels can signify inadequate thyroid hormone production (hypothyroidism)
  • Suppressed TSH levels can point to excessive thyroid hormone production (hyperthyroidism)

Because a single abnormal TSH level can be misleading, T3 and T4 levels must be measured in the blood to further confirm the diagnosis. When circulating in the body, T3 and T4 are bound to transport proteins. Only a small fraction of the circulating thyroid hormones are unbound or free, and thus biologically active. T3 and T4 levels can thus be measured as free T3 and T4, or total T3 and T4, which takes into consideration the free hormones in addition to the protein-bound hormones. Free T3 and T4 measurements are important because certain drugs and illnesses can affect the concentrations of transport proteins, resulting in differing total and free thyroid hormone levels. There are differing guidelines for T3 and T4 measurements.

  • Free T4 levels should be measured in the evaluation of hypothyroidism, and low free T4 establishes the diagnosis. T3 levels are generally not measured in the evaluation of hypothyroidism. [13]
  • Free T4 and total T3 can be measured when hyperthyroidism is of high suspicion as it will improve the accuracy of the diagnosis. Free T4, total T3 or both are elevated and serum TSH is below normal in hyperthyroidism. If the hyperthyroidism is mild, only serum T3 may be elevated and serum TSH can be low or may not be detected in the blood. [14]
  • Free T4 levels may also be tested in patients who have convincing symptoms of hyper- and hypothyroidism, despite a normal TSH.

Antithyroid antibodies

Autoantibodies to the thyroid gland may be detected in various disease states. There are several anti-thyroid antibodies, including anti-thyroglobulin antibodies (TgAb), anti-microsomal/anti-thyroid peroxidase antibodies (TPOAb), and TSH receptor antibodies (TSHRAb). [13]

  • Elevated anti-thryoglobulin (TgAb) and anti-thyroid peroxidase antibodies (TPOAb) can be found in patients with Hashimoto's thyroiditis, the most common autoimmune type of hypothyroidism. TPOAb levels have also been found to be elevated in patients who present with subclinical hypothyroidism (where TSH is elevated, but free T4 is normal), and can help predict progression to overt hypothyroidism. The American Association Thyroid Association thus recommends measuring TPOAb levels when evaluating subclinical hypothyroidism or when trying to identify whether nodular thyroid disease is due to autoimmune thyroid disease. [19]
  • When the etiology of hyperthyroidism is not clear after initial clinical and biochemical evaluation, measurement of TSH receptor antibodies (TSHRAb) can help make the diagnosis. In Graves' disease, TSHRAb levels are elevated as they are responsible for activating the TSH receptor and causing increased thyroid hormone production. [18]

Other markers

  • There are two markers for thyroid-derived cancers.
    • Thyroglobulin (TG) levels can be elevated in well-differentiated papillary or follicular adenocarcinoma. It is often used to provide information on residual, recurrent or metastatic disease in patients with differentiated thyroid cancer. However, serum TG levels can be elevated in most thyroid diseases. Routine measurement of serum TG for evaluation of thyroid nodules is therefore currently not recommended by the American Thyroid Association. [26]
    • Elevated calcitonin levels in the blood have been shown to be associated with the rare medullary thyroid cancer. However, the measurement of calcitonin levels as a diagnostic tool is currently controversial due to falsely high or low calcitonin levels in a variety of diseases other than medullary thyroid cancer. [26] [27]
  • Very infrequently, TBG and transthyretin levels may be abnormal; these are not routinely tested.
  • To differentiate between different types of hypothyroidism, a specific test may be used. Thyrotropin-releasing hormone (TRH) is injected into the body through a vein. This hormone is naturally secreted by the hypothalamus and stimulates the pituitary gland. The pituitary responds by releasing thyroid-stimulating hormone (TSH). Large amounts of externally administered TRH can suppress the subsequent release of TSH. This amount of release-suppression is exaggerated in primary hypothyroidism, major depression, cocaine dependence, amphetamine dependence and chronic phencyclidine abuse. There is a failure to suppress in the manic phase of bipolar disorder. [28]

Ultrasound

Many people may develop a thyroid nodule at some point in their lives. Although many who experience this worry that it is thyroid cancer, there are many causes of nodules that are benign and not cancerous. If a possible nodule is present, a doctor may order thyroid function tests to determine if the thyroid gland's activity is being affected. If more information is needed after a clinical exam and lab tests, medical ultrasonography can help determine the nature of thyroid nodule(s). There are some notable differences in typical benign vs. cancerous thyroid nodules that can particularly be detected by the high-frequency sound waves in an ultrasound scan. The ultrasound may also locate nodules that are too small for a doctor to feel on a physical exam, and can demonstrate whether a nodule is primarily solid, liquid (cystic), or a mixture of both. It is an imaging process that can often be done in a doctor's office, is painless, and does not expose the individual to any radiation. [29]

The main characteristics that can help distinguish a benign vs. malignant (cancerous) thyroid nodule on ultrasound are as follows: [30]

Possible thyroid cancerMore likely benign
irregular borderssmooth borders
hypoechoic (less echogenic than the surrounding tissue)hyperechoic
incomplete "halo"spongiform appearance
significant intranodular / central blood flow by power Dopplermarked peripheral blood flow
microcalcificationslarger, broad calcifications (note: these can be seen in medullary thyroid cancer)
nodule appears more tall than wide on transverse study"comet tail" artifact as sound waves bounce off intranodular colloid
documented progressive increase in size of nodule on ultrasound

Although ultrasonography is a very important diagnostic tool, this method is not always able to separate benign from malignant nodules with certainty. In suspicious cases, a tissue sample is often obtained by biopsy for microscopic examination.

Radioiodine scanning and uptake

Five scintigrams taken from thyroids with different syndromes: A) normal thyroid, B) Graves' disease, diffuse increased uptake in both thyroid lobes, C) Plummer's disease, D) Toxic adenoma, E) Thyroiditis. Thyroid scintigraphy.jpg
Five scintigrams taken from thyroids with different syndromes: A) normal thyroid, B) Graves' disease, diffuse increased uptake in both thyroid lobes, C) Plummer's disease, D) Toxic adenoma, E) Thyroiditis.

Thyroid scintigraphy, in which the thyroid is imaged with the aid of radioactive iodine (usually iodine-123, which does not harm thyroid cells, or rarely, iodine-131), [31] is performed in the nuclear medicine department of a hospital or clinic. Radioiodine collects in the thyroid gland before being excreted in the urine. While in the thyroid, the radioactive emissions can be detected by a camera, producing a rough image of the shape (a radioiodine scan) and tissue activity (a radioiodine uptake) of the thyroid gland.

A normal radioiodine scan shows even uptake and activity throughout the gland. Irregular uptake can reflect an abnormally shaped or abnormally located gland, or it can indicate that a portion of the gland is overactive or underactive. For example, a nodule that is overactive ("hot") -- to the point of suppressing the activity of the rest of the gland—is usually a thyrotoxic adenoma, a surgically curable form of hyperthyroidism that is rarely malignant. In contrast, finding that a substantial section of the thyroid is inactive ("cold") may indicate an area of non-functioning tissue, such as thyroid cancer.

The amount of radioactivity can be quantified and serves as an indicator of the metabolic activity of the gland. A normal quantitation of radioiodine uptake demonstrates that about 8-35% of the administered dose can be detected in the thyroid 24 hours later. Overactivity or underactivity of the gland, as may occur with hyperthyroidism or hypothyroidism, is usually reflected in increased or decreased radioiodine uptake. Different patterns may occur with different causes of hypo- or hyperthyroidism.

Biopsy

A medical biopsy refers to the obtaining of a tissue sample for examination under the microscope or other testing, usually to distinguish cancer from noncancerous conditions. Thyroid tissue may be obtained for biopsy by fine needle aspiration (FNA) or by surgery.[ citation needed ]

Fine needle aspiration has the advantage of being a brief, safe, outpatient procedure that is safer and less expensive than surgery and does not leave a visible scar. Needle biopsies became widely used in the 1980s, though it was recognized that the accuracy of identification of cancer was good, but not perfect. The accuracy of the diagnosis depends on obtaining tissue from all of the suspicious areas of an abnormal thyroid gland. The reliability of fine needle aspiration is increased when sampling can be guided by ultrasound, and over the last 15 years, this has become the preferred method for thyroid biopsy in North America. [32] [ citation needed ]

Treatment

Medication

Levothyroxine is a stereoisomer of thyroxine (T4) which is degraded much more slowly and can be administered once daily in patients with hypothyroidism. [13] Natural thyroid hormone from pigs is sometimes also used, especially for people who cannot tolerate the synthetic version. Hyperthyroidism caused by Graves' disease may be treated with the thioamide drugs propylthiouracil, carbimazole or methimazole, or rarely with Lugol's solution. Additionally, hyperthyroidism and thyroid tumors may be treated with radioactive iodine. Ethanol injections for the treatment of recurrent thyroid cysts and metastatic thyroid cancer in lymph nodes can also be an alternative to surgery.[ citation needed ]

Surgery

Thyroid surgery is performed for a variety of reasons. A nodule or lobe of the thyroid is sometimes removed for biopsy or because of the presence of an autonomously functioning adenoma causing hyperthyroidism. A large majority of the thyroid may be removed (subtotal thyroidectomy) to treat the hyperthyroidism of Graves' disease, or to remove a goiter that is unsightly or impinges on vital structures.[ citation needed ]

A complete thyroidectomy of the entire thyroid, including associated lymph nodes, is the preferred treatment for thyroid cancer. Removal of the bulk of the thyroid gland usually produces hypothyroidism unless the person takes thyroid hormone replacement. Consequently, individuals who have undergone a total thyroidectomy are typically placed on thyroid hormone replacement (e.g. levothyroxine) for the remainder of their lives. Higher than normal doses are often administered to prevent recurrence.[ citation needed ]

If the thyroid gland must be removed surgically, care must be taken to avoid damage to adjacent structures, the parathyroid glands and the recurrent laryngeal nerve. Both are susceptible to accidental removal and/or injury during thyroid surgery.[ citation needed ]

The parathyroid glands produce parathyroid hormone (PTH), a hormone needed to maintain adequate amounts of calcium in the blood. Removal results in hypoparathyroidism and a need for supplemental calcium and vitamin D each day. In the event that the blood supply to any one of the parathyroid glands is endangered through surgery, the parathyroid gland(s) involved may be re-implanted in surrounding muscle tissue.

The recurrent laryngeal nerves provide motor control for all external muscles of the larynx except for the cricothyroid muscle, which also runs along the posterior thyroid. Accidental laceration of either of the two or both recurrent laryngeal nerves may cause paralysis of the vocal cords and their associated muscles, changing the voice quality. A 2019 systematic review concluded that the available evidence shows no difference between visually identifying the nerve or utilizing intraoperative neuroimaging during surgery, when trying to prevent injury to recurrent laryngeal nerve during thyroid surgery. [33]

Radioiodine

Radioiodine therapy with iodine-131 can be used to shrink the thyroid gland (for instance, in the case of large goiters that cause symptoms but do not harbor cancer—after evaluation and biopsy of suspicious nodules has been done), or to destroy hyperactive thyroid cells (for example, in cases of thyroid cancer). The iodine uptake can be high in countries with iodine deficiency, but low in iodine sufficient countries. To enhance iodine-131 uptake by the thyroid and allow for more successful treatment, TSH is raised prior to therapy in order to stimulate the existing thyroid cells. This is done either by withdrawal of thyroid hormone medication or injections of recombinant human TSH (Thyrogen), [31] released in the United States in 1999. Thyrogen injections can reportedly boost uptake up to 50-60%. Radioiodine treatment can also cause hypothyroidism (which is sometimes the end goal of treatment) and, although rare, a pain syndrome (due to radiation thyroiditis). [34]

Epidemiology

In the United States, autoimmune inflammation is the most common form of thyroid disease while worldwide hypothyroidism and goiter due to dietary iodine deficiency is the most common. [35] [4] According to the American Thyroid Association in 2015, approximately 20 million people in the United States alone are affected by thyroid disease. [11] [36] Hypothyroidism affects 3-10% percent of adults, with a higher incidence in women and the elderly. [37] [38] [39] An estimated one-third of the world's population currently lives in areas of low dietary iodine levels. In regions of severe iodine deficiency, the prevalence of goiter is as high as 80%. [40] In areas where iodine-deficiency is not found, the most common type of hypothyroidism is an autoimmune subtype called Hashimoto's thyroiditis, with a prevalence of 1-2%. [40] As for hyperthyroidism, Graves' disease, another autoimmune condition, is the most common type with a prevalence of 0.5% in males and 3% in females. [41] Although thyroid nodules are common, thyroid cancer is rare. Thyroid cancer accounts for less than 1% of all cancer in the UK, though it is the most common endocrine tumor and makes up greater than 90% of all cancers of the endocrine glands. [40]

See also

Related Research Articles

<span class="mw-page-title-main">Goitre</span> Medical condition

A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly.

<span class="mw-page-title-main">Hyperthyroidism</span> Thyroid gland disease that involves an overproduction of thyroid hormone

Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. Some, however, use the terms interchangeably. Signs and symptoms vary between people and may include irritability, muscle weakness, sleeping problems, a fast heartbeat, heat intolerance, diarrhea, enlargement of the thyroid, hand tremor, and weight loss. Symptoms are typically less severe in the elderly and during pregnancy. An uncommon but life-threatening complication is thyroid storm in which an event such as an infection results in worsening symptoms such as confusion and a high temperature; this often results in death. The opposite is hypothyroidism, when the thyroid gland does not make enough thyroid hormone.

<span class="mw-page-title-main">Thyroid</span> Endocrine gland in the neck; secretes hormones that influence metabolism

The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the isthmus (pl.: isthmi). The thyroid gland is a butterfly-shaped gland located in the neck below the Adam's apple. Microscopically, the functional unit of the thyroid gland is the spherical thyroid follicle, lined with follicular cells (thyrocytes), and occasional parafollicular cells that surround a lumen containing colloid. The thyroid gland secretes three hormones: the two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – and a peptide hormone, calcitonin. The thyroid hormones influence the metabolic rate and protein synthesis and growth and development in children. Calcitonin plays a role in calcium homeostasis. Secretion of the two thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary gland. TSH is regulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus.

<span class="mw-page-title-main">Graves' disease</span> Autoimmune endocrine disease

Graves' disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyroid. Signs and symptoms of hyperthyroidism may include irritability, muscle weakness, sleeping problems, a fast heartbeat, poor tolerance of heat, diarrhea and unintentional weight loss. Other symptoms may include thickening of the skin on the shins, known as pretibial myxedema, and eye bulging, a condition caused by Graves' ophthalmopathy. About 25 to 30% of people with the condition develop eye problems.

<span class="mw-page-title-main">Hypothyroidism</span> Endocrine disease

Hypothyroidism is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as poor ability to tolerate cold, a feeling of tiredness, constipation, slow heart rate, depression, and weight gain. Occasionally there may be swelling of the front part of the neck due to goitre. Untreated cases of hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby or congenital iodine deficiency syndrome.

Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism of almost every tissue in the body. It is a glycoprotein hormone produced by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid.

<span class="mw-page-title-main">Hashimoto's thyroiditis</span> Autoimmune disease

Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis and Hashimoto's disease, is an autoimmune disease in which the thyroid gland is gradually destroyed. A slightly broader term is autoimmune thyroiditis, identical other than that it is also used to describe a similar condition without a goitre.

<span class="mw-page-title-main">Levothyroxine</span> Thyroid hormone

Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma. It may also be used to treat and prevent certain types of thyroid tumors. It is not indicated for weight loss. Levothyroxine is taken orally (by mouth) or given by intravenous injection. Levothyroxine has a half-life of 7.5 days when taken daily, so about six weeks is required for it to reach a steady level in the blood.

<span class="mw-page-title-main">Thyroiditis</span> Medical condition

Thyroiditis is the inflammation of the thyroid gland. The thyroid gland is located on the front of the neck below the laryngeal prominence, and makes hormones that control metabolism.

<span class="mw-page-title-main">Toxic multinodular goitre</span> Medical condition

Toxic multinodular goiter (TMNG), also known as multinodular toxic goiter (MNTG), is an active multinodular goiter associated with hyperthyroidism.

<span class="mw-page-title-main">Liothyronine</span> Chemical compound

Liothyronine is a manufactured form of the thyroid hormone triiodothyronine (T3). It is most commonly used to treat hypothyroidism and myxedema coma. It can be taken by mouth or by injection into a vein.

<span class="mw-page-title-main">De Quervain's thyroiditis</span> Medical condition

De Quervain's thyroiditis, also known as subacute granulomatous thyroiditis or giant cell thyroiditis, is a member of the group of thyroiditis conditions known as resolving thyroiditis. People of all ages and genders may be affected.

Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid. TFTs may be requested if a patient is thought to suffer from hyperthyroidism or hypothyroidism, or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy. It is also requested routinely in conditions linked to thyroid disease, such as atrial fibrillation and anxiety disorder.

Desiccated thyroid, also known as thyroid extract, is thyroid gland that has been dried and powdered for medical use. It is used to treat hypothyroidism. It is less preferred than levothyroxine. It is taken by mouth. Maximal effects may take up to three weeks to occur.

<span class="mw-page-title-main">Subacute thyroiditis</span> Medical condition

Subacute thyroiditis refers to a temporal classification of the different forms of thyroiditis based on onset of symptoms. The temporal classification of thyroiditis includes presentation of symptoms in an acute, subacute, or chronic manner. There are also other classification systems for thyroiditis based on factors such as clinical symptoms and underlying etiology.

Postpartum thyroiditis refers to thyroid dysfunction occurring in the first 12 months after pregnancy and may involve hyperthyroidism, hypothyroidism or the two sequentially. According to the National Institute of Health, postpartum thyroiditis affects about 8% of pregnancies. There are, however, different rates reported globally. This is likely due to the differing amounts of average postpartum follow times around the world, and due to humans' own innate differences. For example, in Bangkok, Thailand the rate is 1.1%, but in Brazil it is 13.3%. The first phase is typically hyperthyroidism. Then, the thyroid either returns to normal or a woman develops hypothyroidism. Of those women who experience hypothyroidism associated with postpartum thyroiditis, one in five will develop permanent hypothyroidism requiring lifelong treatment.

<span class="mw-page-title-main">Thyroid nodule</span> Medical condition

Thyroid nodules are nodules which commonly arise within an otherwise normal thyroid gland. They may be hyperplastic or tumorous, but only a small percentage of thyroid tumors are malignant. Small, asymptomatic nodules are common, and often go unnoticed. Nodules that grow larger or produce symptoms may eventually need medical care. A goitre may have one nodule – uninodular, multiple nodules – multinodular, or be diffuse.

<span class="mw-page-title-main">Thyroid hormones</span> Hormones produced by the thyroid gland

Thyroid hormones are any hormones produced and released by the thyroid gland, namely triiodothyronine (T3) and thyroxine (T4). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T3 and T4 are partially composed of iodine, derived from food. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as simple goitre.

Thyroid disease in pregnancy can affect the health of the mother as well as the child before and after delivery. Thyroid disorders are prevalent in women of child-bearing age and for this reason commonly present as a pre-existing disease in pregnancy, or after childbirth. Uncorrected thyroid dysfunction in pregnancy has adverse effects on fetal and maternal well-being. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neurointellectual development in the early life of the child. Due to an increase in thyroxine binding globulin, an increase in placental type 3 deioidinase and the placental transfer of maternal thyroxine to the fetus, the demand for thyroid hormones is increased during pregnancy. The necessary increase in thyroid hormone production is facilitated by high human chorionic gonadotropin (hCG) concentrations, which bind the TSH receptor and stimulate the maternal thyroid to increase maternal thyroid hormone concentrations by roughly 50%. If the necessary increase in thyroid function cannot be met, this may cause a previously unnoticed (mild) thyroid disorder to worsen and become evident as gestational thyroid disease. Currently, there is not enough evidence to suggest that screening for thyroid dysfunction is beneficial, especially since treatment thyroid hormone supplementation may come with a risk of overtreatment. After women give birth, about 5% develop postpartum thyroiditis which can occur up to nine months afterwards. This is characterized by a short period of hyperthyroidism followed by a period of hypothyroidism; 20–40% remain permanently hypothyroid.

In CT scan of the thyroid, focal and diffuse thyroid abnormalities are commonly encountered. These findings can often lead to a diagnostic dilemma, as the CT reflects nonspecific appearances. Ultrasound (US) examination has a superior spatial resolution and is considered the modality of choice for thyroid evaluation. Nevertheless, CT detects incidental thyroid nodules (ITNs) and plays an important role in the evaluation of thyroid cancer.

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  3. ↑ Hollowell, Joseph G.; Staehling, Norman W.; Flanders, W. Dana; Hannon, W. Harry; Gunter, Elaine W.; Spencer, Carole A.; Braverman, Lewis E. (2002). "Serum TSH, T4, and Thyroid Antibodies in the United States Population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III)". The Journal of Clinical Endocrinology & Metabolism. 87 (2): 489–499. doi: 10.1210/jcem.87.2.8182 . PMID   11836274. S2CID   10850710.
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  5. ↑ "Hypothyroidism (Underactive Thyroid)". www.niddk.nih.gov. Retrieved 2016-12-16.
  6. ↑ "Hyperthyroidism". www.niddk.nih.gov. Archived from the original on 2016-12-20. Retrieved 2016-12-16.
  7. 1 2 3 Kasper DL, Fauci AS, Hauser SL, Longo DL, Larry Jameson J, Loscalzo J (2018-02-06). "Thyroid Nodular Disease and Thyroid Cancer". Harrison's principles of internal medicine (Twentieth ed.). New York. ISBN   9781259644047. OCLC   990065894.{{cite book}}: CS1 maint: location missing publisher (link)
  8. ↑ "Final Recommendation Statement: Thyroid Dysfunction: Screening - US Preventive Services Task Force". www.uspreventiveservicestaskforce.org. Retrieved 2018-11-30.
  9. 1 2 3 4 5 6 7 8 9 Hammer GD, McPhee SJ (2018-11-26). "Thyroid Disease". Pathophysiology of disease : an introduction to clinical medicine (Eighth ed.). New York. ISBN   9781260026504. OCLC   1056106178.{{cite book}}: CS1 maint: location missing publisher (link)
  10. ↑ Turkish Endocrinology and Metabolism Association. (2013). Tiroid hastalıkları tanı ve tedavi kılavuzu [Diagnosis and treatment of thyroid diseases guide] (5th Edition). Ankara, Turkey: Miki Matbaacılık.
  11. 1 2 Atasayar S, Guler Demir S (June 2019). "Determination of the Problems Experienced by Patients Post-Thyroidectomy". Clinical Nursing Research. 28 (5): 615–635. doi:10.1177/1054773817729074. PMID   28882054. S2CID   8593999.
  12. ↑ Müller PE, Jakoby R, Heinert G, Spelsberg F (November 2001). "Surgery for recurrent goitre: its complications and their risk factors". The European Journal of Surgery = Acta Chirurgica. 167 (11): 816–21. doi:10.1080/11024150152717634. PMID   11848234.
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  14. 1 2 3 Ross DS, Burch HB, Cooper DS, Greenlee MC, Laurberg P, Maia AL, et al. (October 2016). "2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis". Thyroid (Submitted manuscript). 26 (10): 1343–1421. doi: 10.1089/thy.2016.0229 . PMID   27521067.
  15. ↑ "Hypothyroidism - American Thyroid Association". www.thyroid.org. Retrieved 2017-04-25.
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  17. ↑ "Hyperthyroidism - American Thyroid Association". www.thyroid.org. Retrieved 2017-04-25.
  18. 1 2 "Hyperthyroidism - American Thyroid Association". www.thyroid.org. Retrieved 2016-12-13.
  19. 1 2 "Hypothyroidism - American Thyroid Association". www.thyroid.org. Retrieved 2016-12-13.
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  21. ↑ Batcher EL, Tang XC, Singh BN, Singh SN, Reda DJ, Hershman JM (October 2007). "Thyroid function abnormalities during amiodarone therapy for persistent atrial fibrillation". The American Journal of Medicine. 120 (10): 880–885. doi:10.1016/j.amjmed.2007.04.022. PMID   17904459.
  22. 1 2 Haugen BR (December 2009). "Drugs that suppress TSH or cause central hypothyroidism". Best Practice & Research. Clinical Endocrinology & Metabolism. 23 (6): 793–800. doi:10.1016/j.beem.2009.08.003. PMC   2784889 . PMID   19942154.
  23. 1 2 3 4 5 Gardner DG, Shoback DM, Greenspan FS (eds.). "The Endocrinology of Pregnancy". Greenspan's Basic & Clinical Endocrinology. OCLC   995848612.
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  28. ↑ Giannini AJ, Malone DA, Loiselle RH, Price WA (January 1987). "Blunting of TSH response to TRH in chronic cocaine and phencyclidine abusers". The Journal of Clinical Psychiatry. 48 (1): 25–26. PMID   3100509.
  29. ↑ "Thyroid Nodules - American Thyroid Association". www.thyroid.org. Retrieved 2016-12-13.
  30. ↑ "Diagnostic approach to and treatment of thyroid nodules". www.uptodate.com. Retrieved 2016-12-13.
  31. 1 2 "Radioactive Iodine - American Thyroid Association". www.thyroid.org. Retrieved 2016-12-14.
  32. ↑ Dean DS, Gharib H (2000). "Fine-Needle Aspiration Biopsy of the Thyroid Gland". In Feingold KR, Anawalt B, Blackman MR, Boyce A, Chrousos G, Corpas E, et al. (eds.). Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc. PMID   25905400 . Retrieved 29 Jun 2020.
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  34. ↑ Shah KK, Tarasova VD, Davidian M, Anderson RJ (2014-06-01). "Non-Neoplastic Thyroid Disorders-Clinical and Case Reports". Endo Meetings. Meeting A bstracts: SAT–0523–SAT–0523.
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  36. ↑ "Prevalence and Impact of Thyroid Disease". American Thyroid Association.
  37. ↑ Gharib H, Tuttle RM, Baskin HJ, Fish LH, Singer PA, McDermott MT (2004). "Subclinical thyroid dysfunction: a joint statement on management from the American Association of Clinical Endocrinologists, the American Thyroid Association, and the Endocrine Society". Endocrine Practice. 10 (6): 497–501. doi:10.4158/ep.10.6.497. PMID   16033723.
  38. ↑ Fatourechi V (2009). "Subclinical hypothyroidism: an update for primary care physicians". Mayo Clinic Proceedings. 84 (1): 65–71. doi:10.4065/84.1.65. PMC   2664572 . PMID   19121255.[ dead YouTube link ]
  39. ↑ Villar HC, Saconato H, Valente O, Atallah AN (July 2007). "Thyroid hormone replacement for subclinical hypothyroidism". The Cochrane Database of Systematic Reviews. 2007 (3): CD003419. doi:10.1002/14651858.CD003419.pub2. PMC   6610974 . PMID   17636722.
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