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This glossary aims to provide accurate definitions of key terms. Words in italics have their own explanations. If you feel there are terms that should be added to the glossary, please send an e-mail to info@excemed.org with your suggestion.
American Association of Clinical Endocrinologists (North America)
Describes how patients follow (or have steady observance of) any therapeutic regimen agreed between themselves and their healthcare practitioners.
Associazione Medici Endocrinologi (Italy)
Protein found in the blood that plays a key function in immune response. An antibody is produced following the introduction of an antigen in the body; a specific antibody is designed to combine with the specific antigen that triggered its production
Foreign substance or toxin in the body. Induces an immune response, leading to the production of an antibody
Also known as antimicrosomal antibody. Antibody against peroxidase
Asia-Oceania Thyroid Association
American Thyroid Association
Body mass index. A subject’s weight in kg divided by his or her height in m2. There are differences in BMI levels that constitute normal, overweight and obese situations, depending on the ethnic origin of the individual.
Blood pressure.
British Thyroid Association (United Kingdom)
Abbreviation for coronary artery disease.
Abbreviation for coronary heart disease.
See Hashimoto’s disease
Continuing medical education. Common term for medical education that helps physicians, surgeons and other key healthcare professionals to refresh their skills and knowledge.
Central nervous system: the brain and spinal cord.
Higher function of the brain, concerned with generating and working with ideas, including thinking, learning, remembering and reasoning. There is some evidence that hypothyroidism is associated with impairment of cognitive function in later life, although such findings remain controversial.
Thyroid nodule that does not concentrate radioactive isotopes in a thyroid scan. Non-functioning nodules have about 20% risk of malignancy
Describes how patients follow a treatment regimen in accordance with the advice given to them by their health care professional. Thus, people comply well or badly with things such as medication (e.g. taking the right tablets in the right numbers at the right times), or special diets (e.g. eating the right foods in the right amounts and avoiding other foods, etc.).
Condition observed in infants born in areas where iodine deficiency disorder and hypothyroidism are common. May also be caused by thyroid agenesis/dysgenesis or a defect in thyroid hormone synthesis (dyshormonogenesis). Congenital hypothyroidism may also be associated with neck dysmorphology, cretinism and consumptive hypothyroidism (haemaingioma)
Hypothyroidism in utero or soon after birth, due to any cause (most commonly due to severe iodine deficiency during pregnancy), may have major effects on the fetus. If untreated, cretinism may lead to physical stunting, bone and soft tissue dystrophy, and mental retardation in the infant. Cretinism is also known as infantile myxoedema. The clinical manifestation of cretinism depends on the severity and onset of hypothyroidism in the fetus or neonate
Cardiovascular
Cardiovascular disease. Diabetes is associated with direct alterations in normal cardiovascular function.
Disability-associated life years
Diastolic blood pressure; pressure of blood against arterial walls during cardiac relaxation phase (phase between heart beats).
Also known as monodeionodinase or iodide peroxidase. Enzyme involved in deactivation or activation of T4 to T3
A broad term to encompass the physical and cognitive changes accompanying growth, usually applied to young people. Optimizing nutrition to maintain normal development is important: iodine deficiency remains a co-factor in the development of thyroid disorders in some countries
Thyroid cancer that has metastasized. Should not be confused with differentiated thyroid cancer (DTC)
Diabetes mellitus. A group of metabolic conditions characterised by hyperglycaemia due to defects in insulin secretion, action or both. It is important to ensure that blood pressure is effectively monitored in people with DM (type 1 or type 2).
Differentiated thyroid cancer is a cancer of follicular epithelial cells within the thyroid and is the most common thyroid cancer observed. DTC is treated with surgery, which requires precision and specialist training; complete surgical resection is a key determinant of eventual outcome. Postoperatively, some patients require radioactive iodine therapy
Aberrant physical development, observed on physical examination. Congenital hypothyroidism might lead to dysmorphology in affected newborn.
Ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity.
European Accreditation Council for Continuing Medical Education
Environmental chemicals that may mimic hormones and thereby cause disruption in endocrine function, including thyroid function
Enzymes are proteins that act as catalysts for biochemical reactions essential to life.
Endocrinology Society
European Society of Endocrinology
European Society of Molecular Endocrinologists
European Thyroid Association
Term used to describe a person who has normal thyroid function
Term that describes several of the higher functions of the brain. Examples of executive function include exercising will, insight, or judgement, coordinating use of resources (such as memory) to achieve a desired goal, planning tasks, generating strategies or placing complex activities in order to complete a larger task, correcting errors, troubleshooting, adapting behaviour in the light of new information, generating behavioural responses based on actions that are not already well learned, or performing well in situations that require overcoming temptation or force of habit. Studies in populations with iodine deficiency and related thyroid disorder have found reduced executive function, increased depression/anxiety and poor working memory, on average, compared with populations without iodine deficiency and related thyroid disorder.
Protrusion of the eye from the orbit, typically associated with hyperthyroidism (Graves’ disease)
Thyroid follicular epithelial cell neoplasm, not belonging to papillary thyroid carcinoma, with evidence of capsular and/or vascular invasion. Second most common form of thyroid cancer, which affects the follicular cells.
Gestational diabetes mellitus
A sequence of DNA that determines the structure of a particular protein.
The pattern of mutations present in particular genes, at the level of the DNA of an individual.
Abnormal swelling of the neck or larynx, resulting from enlargement of the thyroid gland; often due to underlying thyroid disease.
Diffuse smooth goitre describes a thyroid gland that is larger than normal but feels smooth. Typically, smooth goitre is observed in people with colloid goitre, Graves’ disease or Hashimoto’s disease.
Nodular goitres nay be multinodular (where the thyroid feels lumpy) or may involve a single nodule (which could be a fluid-filled cyst, a solid or semi-solid tumour. Many people with a goitre may be euthyroid
General practitioner/family physician
Autoimmune disease that is commonly observed in people with Graves’ disease, causing orbitopathy or exophthalmos
An autoimmune thyroid disorder that usually causes hyperthyroidism, due to the overproduction of antibodies that act like TSH. These antibodies trigger overactivity of thyroid hormone production in the thyroid gland, which results in hyperthyroidism. Named after Dr Robert Graves
Also known as chronic autoimmune thyroiditis, this is the most common form of hypothyroidism. Hashimoto’s disease is associated with Tg/TPO thyroid antibody positivity
Glycosylated haemoglobin
Healthcare professional
We each have two copies of each gene. A subject with a particular mutation of one gene, but not the other, is said to be heterozygous for that mutation.
We each have two copies of each gene. A subject with an identical mutation of both genes is said to be homozygous for that mutation.
Nodule with increased radioactive isotope uptake on the thyroid scan, often associated with hyperthyroidism
Health-related quality of life; describes the effect that a medical condition (and/or its therapy) has on a patient’s physical and occupational function, psychological state, level of social interaction and somatic sensation.
Also known as overactive thyroid or thyrotoxicosis. Hyperthyroidism describes a state where the thyroid produces too much of the hormone thyroxines (T4 and/or T3). Common causes include Graves’ disease, toxic multinodular goitre or subacute thyroiditis
Serum levels of thyroid hormones are regulated by the hypothalamic-pituitary-thyroid axis. In the brain, the hypothalamus secretes thyrotropin releasing hormone (TRH), which controls the secretion of thyrotropin (also known as thyroid stimulating hormone, TSH) by the pituitary gland. TSH stimulates the thyroid gland to synthesize and secrete thyroid hormones (T4 and T3) Thyroid hormones provide feedback to the hypothalamus and pituitary gland resulting in inhibition or stimulation of TRH and TSH release depending on the level of thyroid hormone, leading to normal thyroid hormone homeostasis
Brain region that regulates the production and secretion of TRH
A condition where not enough thyroid hormones are produced for the body’s needs. Primary hypothyroidism is caused by loss of functional thyroid tissue, defects in thyroid hormone biosynthesis and release (caused by iodine deficiency, administration of certain drug classes, or congenital deficits). Secondary (central) hypothyroidism is associated with functional deficits in TSH; consumptive hypothyroidism is rare and is associated with haemiangiomas or increased type 2 or type 3 deiodinase activity, which degrades T4/T3
Iodine deficiency disorder
International Diabetes Federation
Impaired glucose tolerance
Ischaemic heart disease
International Insulin Foundation
A mutation where additional DNA (one or more base pairs) is added to the gene
DNA sequences within a gene that are not represented in the final protein. RNA sequences arising from introns will be removed during processing, to form the messenger RNA that will be used for translation into protein
Iodine is an essential component of thyroid hormone; dietary iodine is absorbed in the small intestine and transported in plasma to the thyroid. Good dietary sources of iodine include seafood, dairy produce, iodised salt; the RDI is 150 μg; intakes < 50μg/day are associated with goitre
See IDD
Institute for Studies on Diabetes Foundation
Area that connects the two lobes of the thyroid gland
L-thyroxine (L-T4), also known as levothyroxine sodium or levothyroxine, is a synthetic hormone, chemically identical to thyroxine (T4). L-thyroxine is administered as replacement or supplemental therapy to people with thyroid disorders such as hypothyroidism, or requiring TSH suppression (e.g. thyroid cancer, nodular disease, goitre)
Also known as liothyronine. Synthetic pharmaceutical preparation of the levorotatory isomer of triiodothyronine.
Latin American Thyroid Society.
Middle East and North Africa
A lack of normal development of intellectual capacities. Iodine deficiency may lead to severe mental retardation early in life.
Metabolic syndrome
An abnormally small head due to a failure of growth of the brain. Microcephaly is evident in some children with congenital hypothyroidism
Methimazole drug treatment for hyperthyroidism that reduces the amount of thyroid hormone produced by inhibiting TPO. Less hepatotoxic than PTU, but not suitable for use in the first trimester of pregnancy
Medullary thyroid cancer accounts for ~5% of all thyroid cancers and is the third most common type of thyroid cancer. MTC originates from the parafollicular cells (C cells), which release the hormone calcitonin. MTC can be sporadic, or inherited. Sporadic MTC is the most common form; inherited MTC is caused by a mutation in the RET proto-oncogene. The 5-year survival rate for MTC is reported at > 80% but < 90%.
Vast numbers of proteins are required to support life. The structures of these proteins are determined by genes, made up of strands of DNA. Mutations are changes in the DNA sequence that may alter the way that proteins work. Papillary thyroid cancers are often associated with mutations in the BRAF gene (the gene for the B-type Raf kinase, BRAF). Medullary thyroid cancer is linked with a mutation in the RET proto-oncogene
Swelling of the skin and underlying tissues giving a waxy consistency, typical of patients with underactive thyroid glands. Synonymous with hypothyroidism, especially severe disease
Also known as desiccated thyroid. Produced using pig thyroid glands. Natural thyroid drugs therefore contain all thyroid hormones
Thyroid nodules are common, and may be asymptomatic and associated with a euthyroid state. However, nodules should always be investigated: they carry a < 5% risk of malignancy. Nodules arise within an otherwise normally-functioning thyroid gland and manifest as a lump in the throat; in individuals with low BMI, lumps in the neck may be observed on standard examination. Some nodules are thyroid cysts, which are fluid-filled or contain solid and fluid components; occasionally the solid components may be malignant. Nodular disease is characterised using ultrasound; histopathology (using fine-needle aspiration biopsy) may also be undertaken. Measurement of TSH, thyroid function tests (TFT) or anti-thyroid antibodies may be performed, to identify functional thyroid disorders
May be multinodular (where the thyroid feels lumpy) or may involve a single nodule (which could be a fluid-filled cyst, a solid or semi-solid tumour). Many people with a goitre may be euthyroid
Oral antidiabetes drugs
Oral glucose tolerance testing
A type of well-differentiated thyroid cancer that appears as an irregular solid or cystic mass or nodule in a normal thyroid parenchyma. The most common type of thyroid cancer, globally. See thyroid cancer
Usually four small glands behind the thyroid that secrete parathyroid hormone. Involved in calcium and bone metabolism
Small gland, situated in a bony space behind the eyes at the base of the brain. Secretes thyroid stimulating hormone (TSH) as part of the closed-feedback mechanism that results in normal thyroid hormone homoestasis
Inflammation of the thyroid occurring after pregnancy, which may cause short-term hyperthyroidism followed by hypothyroidism
Provider-patient communication
Postprandial hyperglycaemia
Propylthiouracil is a second-line treatment for hyperthyroidism. Reduces the amount of thyroid hormone produced, by inhibiting TPO and by inhibiting peripheral T4/T3 conversion. Can be administered in first trimester of pregnancy
Broad description used for any of the isotopes of iodine, especially I131 or I123, which are used as tracers in medicine. Radioiodine (also known as RAI; I-131) is administered orally to some patients with benign or malignant thyroid disorders: malignant thyroid cells absorb the radioactive iodine. This therapy can be effective at offering targeted radiotherapy, even for metastatic disease. RAI is also used to treat hyperthyroidism by reducing the volume of the thyroid. RAI aims to destroy enough thyroid tissue so that the patient becomes euthyroid or hypothyroid. Radioactive iodine is taken up by the iodide transporter in the thyroid; the follicular cell is then destroyed by radioactivity
Randomized clinical trial.
Stanford Asia Pacific program for hypertension and insulin resistance
Systolic blood pressure. Highest force of blood against arterial walls during the contraction phase of cardiac muscle.
Rare inflammatory condition in the thyroid gland, usually associated with a recent history of viral upper respiratory tract infection and more common in middle-aged female patients. Associated with pain. Under investigation, anti-thyroid antibodies are undetectable or present at low levels; biopsy of the thyroid gland shows giant-cell inflammation. The condition is usually self-limited. In mild cases, treatment aims to reduce pain and inflammation (using simple anti-inflammatory agents). If hyperthyroidism is identified, this should be treated with beta-blockers. More severe cases can be treated with steroids, to control inflammation
Abbreviated as SCH. Also known as subclinical hypothyroid disorder. SCH describes a state where a patient exhibits increased serum TSH levels, but circulating T4 and T3 concentrations are within the population reference range
Type 2 diabetes mellitus
thyroid dysfunction
Thyroglobulin (Tg); a 660 kDa dimeric protein that is only produced by cells in the thyroid gland. In patients with thyroid cancer, absence of Tg is a marker that the tumour has been eradicated
Serum glycoprotein, synthesized in the liver. Binds tightly to thyroxine but less firmly to triiodothyronine, thereby preventing their removal from the blood and releasing them as needed elsewhere in the body
Thyroid cancer is rare, but the incidence of differentiated thyroid cancer (DTC) is increasing globally, to the extent that it is the most frequently observed endocrine cancer. However, the five-year survival rate for DTC is high, at 97.7%. Histologically, thyroid cancer is defined as papillary thyroid cancer, thyroid follicular cell cancer, medullary thyroid cancer and other subtypes (such as lymphoma, sarcoma). DTC is a cancer of the follicular epithelial cells in the thyroid. Papillary cancer comprises about 85% of cases, ~10% have follicular histology, and the remainder are oxyphil or Hürthle cell tumours. DTC is treated with surgical excision (thyroidectomy); disease recurrence or persistence is most likely to occur in metastatic lymph nodes. Accurate postoperative disease staging is critical, to aid decisions relating to prognosis and further management. Radioactive iodine is administered in some cases, either for thyroid tissue remnant ablation, or to treat any residual disease or metastases. MTC accounts for ~5% of all thyroid cancers and is the third most common type of thyroid cancer. MTC originates in the parafollicular cells (C cells), which release calcitonin. MTC can be sporadic, or inherited. Sporadic MTC is the most common form; inherited MTC is caused by a mutation in the RET porto-oncogene.
The thyroid gland is an endocrine gland in the neck. It synthesizes the thyroid hormones tetraiodothyronine (T4) and triiodothyronine (T3), and plays an important role in cell and organ function; the thyroid works with the hypothalamus and pituitary gland in a closed feedback loop, to regulate the production of hormones responsible for metabolism, growth and maturation
Also known as TPO. Enzyme within the thyroid that catalyzes the incorporation of iodide to tyrosine residues in the production of thyroxine. This process is called organification.
Also known as thyrotropin, TSH is a glycoprotein hormone, secreted by thyrotrope cells in the pituitary gland. TSH regulates the production of thyroxine (T4), and subsequently T3. TSH is the most sensitive marker of thyroid status. Small changes in free T4 can result in large changes in TSH. Measuring TSH is important when thyroid dysfunction is suspected
Also known as tetraiodothyronine, T4. Iodine-containing hormone secreted by the thyroid gland. Prohormone of T3. Primary function of T4 is to increase the rate of cell metabolism
Condition associated with hyperthyroidism. Also known as toxic nodular goitre, or toxic nodular struma. This is a multinodular swelling in the region of the body where the thyroid gland is found
Countries that are classified between ‘developing’ and ‘developed’.
Thyrotropin-releasing hormone produced by the hypothalamus, TRH is important for the regulation of TSH and prolactin secretion. TRH is the simplest hypothalamic neurohormone. Tripeptidal, its sequence is glutamic acid-histidine-proline
Also known as T3, triiodothyronine is an iodine-containing thyroid hormone, liberated from thyroglobulin, that helps to control metabolism but also inhibits secretion of thyrotropin in the pituitary gland. T3 production is activated by TSH in a closed feedback loop (see hypothalamic-pituitary-thyroid axis). T3 has effects on target tissues that are approximately four times more potent than the effects of T4; approximately 20% of thyroid hormone is produced as T3, with the remainder produced as T4
Thyroid stimulating hormone
Years of life with disability
Years of life lost