Thyroid Glossary of Terms

Disclaimer: While every attempt is made to ensure the accuracy of the information contained herein, a certain amount of conjecture is admitted. For a complete understanding, please consult your physician, and or endocrinologist for a more detailed understanding. Excerpts are taken from a variety of information sources, including the Textbook of Medical-Surgical Nursing by Brunner, Emerson, Ferguson, and Suddarth 2nd Edition, and informational pamphlets from the Thyroid Foundation of America, Inc. plus other sources, dictionaries, etc.

Since this Glossary is for Thyroid Cancer Group patients, perhaps the first step is the identification of the four different types of thyroid cancer: papillary, follicular (most common, mixed papillary-follicular), medullary (solid, with amyloid struma), and anaplastic (rare).


ablation: Removal of a body part or the destruction of its function, as by a surgical procedure, morbid process, or noxious substance.

anaplastic carcinoma: accounts for 10% or less of thyroid cancer and occurs mostly in elderly patients, females slightly more than males. The tumor is characterized by rapid and painful enlargement, and about 80% of patients die within 1 year of diagnosis. Rapid enlargement of the thyroid gland may also suggest thyroid lymphoma, particularly if found in association with high concentrations of thyroid antimicrosomal antibodies and Hashimoto's thyroiditis.

antithyroid agents: Drugs; methamazole (Tapazole) or Propylthiouracil (PTU), drugs used to make it more difficult for iodine to get into your thyroid gland.

anxiety: Apprehension of danger and dread accompanied by restlessness, tension, tachycardia, and dyspnea unattached to a clearly identifiable stimulus.

Assay: different labs use different scales of measurement. This is why, for comparison, it is crucial to be sure that the same lab, or at least the same scale, is used for every draw. It also means that you cannot compare your results to someone else's and make any useful conclusion; it's all apples and oranges.

beta adrenergic blocking agents: drugs which block the action of the thyroid hormone on your body.

biopsy: procedure of obtaining a tissue sample from a suspect area often used in the determination of whether the tissue is cancerous or not.

calcitonin level: a normal cell produced by the body which helps regulate the balance of calcium between the blood and bones. When mtc patients prove to be cancer free, it is likely they will not have a 'normal' calcitonin level. The docs don't know why this is. The goal, then, is not to get back to the 'norm', but to level out. If you happen to get back to 'norm,' that's great; it's also very unusual.

cancer: basically normal cells multiplying at an uncontrolled rate.

carcinogen emryonic agent (CEA): most cancers also produce it, which is a marker for the presence of cancer. Everyone has a certain level of carcinogens in the blood stream because of trace amounts of carcinogens that we inhale, eat, etc. When it gets above a certain "norm," however, it is indicative that a tumor is present. MTC often produces CEA - but not always.

CAT: Abbreviation for computerized axial tomography.

C-cell: have nothing to do with thyroid functions; they just happen to reside there. Among other things, they produce a normal hormone called "calcitonin," which helps regulate the balance of calcium between your blood and bones.

CT: Abbreviation for computed tomography.

cyst: an abnormal collection of fluid within a definite sac or wall.

cytomel: drug T3 based drug.

dermabrasion: Dermal abrasion, the surgical planning of the skin. The procedure involves the removal of the epidermis and some superficial dermis while preserving enough of the dermis to allow re-epithelialization of the dermabraded areas.

Diffuse toxic goiter: Hyperthyroidism.

endo: see endocrinologist.

endocrinologist: One who specializes in endocrinology, A specialist who studies the endocrine glands, these include the thyroid gland, parathyroid glands, the pancreas, the adrenal gland, and the pituitary gland.

endometrioid carcinoma: adenocarcinoma of the ovary or prostate resembling endometrial adenocarcinoma, possibly arising from ovarian foci of endometriosis.

eosin: A derivative of flourescein used as a fluorescent acid dye for cytoplasmic stains and counterstains in histology and in Romanovsky-type blood stains.

eosinophilic: Staining readily with eosin dyes; denoting such cell or tissue elements.

euthyroid: normal thyroxine level condition, thyroid hormone level in normal balance.

exophthalmos: a thyroid related condition where one or both of the eyes may appear protruded. This is a less common condition associated with Graves' disease.

FSH: Abbreviation for follicle-stimulating hormone. Follicular carcinoma accounts for about 15% of thyroid cancer and is more common in the elderly. It is more malignant than papillary carcinoma, spreading hematogenously with distant metastases. It also is occasionally associated with a history of radiation exposure and is more frequent in females than in males. Treatment for follicular cancer of any size requires near-total thyroidectomy with postoperative radioiodine ablation of residual thyroid tissue similar to the patient with papillary cancer. Metastases appear to be more amenable to radioiodine therapy.

follicullar thyroid cancer: The normal thyroid gland is made up of sphere-shaped structures called follicles. When a thyroid cancer arises from the cells which normally make up these follicles, the cancer is called follicular cancer.

free T4: The FT4 measures the concentration of free thyroxine, the only biologically active fraction, in the serum. The free thyroxine is not affected by changes in concentrations of binding proteins such as TBG and thyroid binding prealbumin. Thus such conditions as pregnancy, or estrogen and androgen therapy do not affect the FT4.

GP: General Practitioner.

goiter: a chronic enlargement of the thyroid gland, not due to a neoplasm, occurring endemically in certain localities, especially mountainous regions, and sporadically elsewhere.

Graves: is the type of hyperthyroidism caused by a generalized overactivity of the entire thyroid gland. It is also called "diffuse toxic goiter,", diffuse because because the entire thyroid gland is involved in the disease process; "toxic" because the patient appears hot and flushed, as if feverish due to an infection; and "goiter" because the thyroid gland enlarges in this condition. One potential symptom is that the eyes may appear enlarged due to the elevation of the upper eye lids.

Hashimoto's struma: also referred to as Reidel's struma, chronic thyroiditis.

Hurthle Cells: Hürthle cell, Askanazy cell; a large, granular eosinophilic cell derived from thyroid follicular epithelium by accumulation of mitochondria, e.g., in Hashimoto's disease.

hyper: see hyperthyroidism.

hyperthyroidism: The term used to refer to any condition in which there is too much thyroid hormone in the body. This most commonly results from a generalized over-activity of the entire thyroid gland, a condition also known as diffuse toxic goiter or Graves' disease. Common symptoms may include nervousness, irritability, increased perspiration, thinning of your skin, fine brittle hair, and muscular weakness especially involving the upper arms and thighs. Your hands may shake and your heart may race. Your bowel movements may increase in frequency, though diarrhea is uncommon.

hyperparathyroidism: The presence of excess parathyroid hormone in the body resulting in disturbance of calcium metabolism with increase in serum calcium and decrease in inorganic phosphorus, loss of calcium from bone, and renal damage with frequent kidney-stone formation.

hyperplasia: numerical hypertrophy; quantitative hypertrophy; an increase in number of cells in a tissue or organ, excluding tumor formation, whereby the bulk of the part or organ may be increased. See also hypertrophy.

hypo: see hypothyroidism.

hypoparathyroidism: Deficiency of parathyroid hormone (PTH) in the body. Decreased levels of PTH lead to low levels of calcium and high levels of phosphorus in the blood. This imbalance can lead to problems with bones, muscles, skin, and nerve endings.

hypothyroidism: a condition in which the amount of thyroid hormones in the body is below normal. This is the most common form of thyroid function abnormality, and is far more common than an overactive thyroid. Symptoms include feeling run down, slow, depressed, cold, tired, and you may lose interest in normal daily activities. Other symptoms may include dryness and brittleness of the hair, dry and itchy skin, constipation, muscle cramps, and increased menstrual flow in women.

LH: Abbreviation for luteinizing hormone.

levothroid: drug; different brands of the thyroid hormone T4 or levo-thyroxine.

Levo-Thyroxine: T4.

Levoxyl: drug; different brands of the thyroid hormone T4 or levo-thyroxine.

lobectomy: Excision of a lobe of any organ or gland.

lymph node: lymphonodus.

lymphonodus: lymph gland; lymph node; lymphaden; lymphoglandula; nodus lymphaticus; one of numerous round, oval, or bean-shaped bodies located along the course of lymphatic vessels, varying greatly in size (1 to 25 mm in diameter) and usually presenting a depressed area, the hilum, on one side through which blood vessels enter and efferent lymphatic vessels emerge. The structure consists of a fibrous capsule and internal trabeculae supporting lymphoid tissue and lymph sinuses; lymphoid tissue is arranged in nodules in the cortex and cords in the medulla of a node, with afferentessels entering at many points of the periphery

MTC: medullary thyroid cancer.

malignant: (1) Resistant to treatment; occurring in severe form, and frequently fatal; tending to become worse and lead to an ingravescent course. (2) In reference to a neoplasm, having the property of locally invasive and destructive growth and metastasis.

malignancy: The property or condition of being malignant.

medullary: medullar; relating to the medulla or marrow.

Medullary (solid) carcinoma: of the thyroid may occur as a sporadic form (usually unilateral) or as a familial form (frequently bilateral), transmitted as an autosomal dominant trait. Patients are usually 15 years of age. Pathologically there is a proliferation of parafollicular cells ("C" cells) that produce excessive calcitonin, a hormone that can lower serum Ca and phosphate (PO4), and there are characteristic amyloid deposits that stain with Congo red. Metastases are via lymphatics to cervical and mediastinal nodes, but there may also be metastases to liver, lungs, and bone, with dense calcifications. The usual presentation is that of an asymptomatic thyroid nodule, although many cases are now diagnosed during routine screening of affected kindreds with multiple endocrine neoplasia (MEN) types II or III before a palpable tumor develops. Medullary carcinoma of the thyroid may have a dramatic biochemical presentation when it is associated with ectopic production of hormones such as ACTH, vasoactive intestinal polypeptide, prostaglandins, kallikreins, and serotonin. This tumor is a component of Sipple's syndrome, which is characterized by medullary carcinoma of the thyroid, pheochromocytoma, and hyperparathyroidism. All 3 disorders are not always found in the same patient. Pheochromocytoma is present in 50 to 75%; hyperparathyroidism, in 50%. Additional findings not regularly associated with this syndrome include disorders of the neural ectoderm, including mucosal neuromas; megacolon; pectus excavatum; poorly developed musculature; and marfanoid appearance, with long arms and fingers. When these associated conditions occur, the syndrome is classified as MEN, type III; hyperparathyroidism is not present in this subset.

Medullary Thyroid Cancer (MTC): C-cells multiplying at an uncontrolled rate creating an increasing number of cells producing calcitonin. By measuring this overproduction, the docs can tell if you have mtc. As yet, there is no established correlation between the calcitonin level and the amount of tumor; the only conclusion that can currently be drawn from an increasing level is the continuing presence of MTC, not an increase in tumor size.

metastases: (1) The shifting of a disease, or its local manifestations, from one part of the body to another, as in mumps when the symptoms referable to the parotid gland subside and the testis becomes affected. (2) The spread of a disease process from one part of the body to another, as in the appearance of neoplasms in parts of the body remote from the site of the primary tumor; results from dissemination of tumor cells by the lymphatics or blood vessels, or by direct extension through serious cavities or subarachnoid or other spaces. (3) Transportation of bacteria from one part of the body to another, through the bloodstream (hematogenous metastasis) or through lymph channels (lymphogenous metastasis).

MRI: Magnetic Resonance Imaging.

nodule: A small node. See also nodulus.

nodulus: (1) a small node. (2) The posterior extremity of the inferior vermis of the cerebellum, forming with the velum medullare posterius the central portion of the flocculonodular lobe.

occult: (1) Hidden; concealed; not manifest. (2) Denoting a concealed hemorrhage, the blood being so changed as not to be readily recognized. See occult blood. (3) In oncology, a clinically unidentified primary tumor with recognized metastases.

PCP: primary care physician.

palpitations: trepidatio cordis; forcible pulsation of the heart, perceptible to the patient, usually with an increase in frequency or force, with or without irregularity in rhythm.

papilla: a nipple-like projection.

Papillary carcinoma is the most common thyroid malignancy (60 to 70% of all thyroid cancers). Females are affected 2 to 3 times more often than males. It is more frequent in the young, but it takes a more malignant course in the elderly. It is often associated with a history of radiation exposure and spreads via the lymphatics. Lateral aberrant thyroid rests may be found that are actually occult metastases with a benign histologic appearance. These well- differentiated cancers are highly TSH-dependent and may develop in hypothyroid glands secondary to Hashimoto's thyroiditis. Many papillary cancers contain follicular elements, but this does not alter the basic biology of the tumor. Treatment for small (< 1.5 cm), encapsulated tumors localized to one lobe is lobectomy and isthmectomy. Thyroid hormone in suppressive doses is given to minimize chances of regrowth or produce regression of any microscopic remnants of papillary carcinoma; surgery is almost always curative. Large (1.5 cm) or diffusely spreading tumors require total or near-total thyroidectomy with postoperative radioiodine ablation of residual thyroid tissue with 150 mCi 131I administered when the patient is hypothyroid. Repeat treatment may be required every 6 to 12 months to achieve ablation of remaining thyroid tissue. Replacement doses of L-thyroxine are given afterward at an average oral dose of 100 to 150 µg/day.

papillary carcinomas: multiple projections giving them a fern or frond-like appearance. In a small state these are commonly found in most thyroids, when these papillary carcinoma grow enough to form a lump in the thyroid gland, it is considered clinically important for it is likely to continue to enlarge and may spread elsewhere in the body. Such papillary tumors make up about 60% to 70% of all thyroid cancers, and can occur at any age.

papillary: Relating to, resembling, or provided with papillae.

parathyroid: (1) Adjacent to the thyroid gland. (2) Glandula parathyroidea.

pathological: (1) Pertaining to pathology. (2) Morbid or diseased; resulting from disease.

PET scan: Positron Emission Tomagraphy; identifies differences in how quickly cells metabolize glucose. Apparently cancer cells metabolize glucose more quickly than normal cells.

postpartum thyroiditis: An inflammation of the thyroid gland which normally occurs after the birth of a child, for reasons unknown normally after the second or later birth. It is presumedly cause by antibodies (proteins) in the body which attack and damage the thyroid gland. This is a common disorder which frequently goes unrecognized.

Propranolol: drug; Inderal.

RAI: Abbreviation for Radioactive Iodine.

radioactive iodine: usually administered in the form of a capsule or in water (it is odorless and tasteless), the Radioactive iodine is quickly take up by the overactive thyroid cells. The results is that the thyroid shrinks in size, the thyroid hormone production falls, and blood levels return to normal with restoration of good health. Occasionally a second treatment is given to further control the thyroid hormone output. After administration your Nuclear Medicine technician will usually monitor the amount of intake by the thyroid (scanning), and looking for hot spots or glows.

resin T3 uptake: The resin T3 uptake is used to assess the binding capacity of the serum for thyroid hormone. This is used to help determine if the Total T4 is reflecting the free T4, or if abnormalities in binding capacity are responsible for changes in T4 values.

RET proto-oncogene: blood test to determine if the Medullary Thyroid Cancer is sporadic or familial (hereditary)

Sensitivity: the lab tests can run the test on the same sample of blood twice and get two slightly different numbers. Remember, they are counting tiny hormone levels; the digits are bound to be different each time. What counts is how far different. 

Synthroid: drug; different brands of the thyroid hormone T4 or levo-thyroxine.

thyca: Thyroid Cancer.

thyroglobulin: (1) iodoglobulin; thyroprotein; a thyroid hormone-containing protein, usually stored in the colloid within the thyroid follicles; biosynthesis of thyroid hormone entails iodination of the tyrosine moieties of this protein and the combination of two iodotyrosines to form thyroxine, the fully iodinated thyronine; secretion of thyroid hormone requires proteolytic degradation of thyroglobulin, with the attendant release of free hormone. (2) A substance obtained by the fractionation of thyroid glands from the hog, Sus scrofa, containing not less than 0.7% of total iodine; used as a thyroid hormone in the treatment of hypothyroidism.

thyroid: (1) Resembling a shield; denoting a gland (glandula thyroidea) and a cartilage of the larynx (cartilago thyroidea) having such a shape. (2) The cleaned, dried, and powdered thyroid gland obtained from one of the domesticated animals used for food and containing 0.17 to 0.23% of iodine; used in the treatment of cretinism and myxedema, in certain cases of obesity, and in skin disorders.

thyroiditis: inflammation of the thyroid gland.

thyroid storm: thyrotoxic crisis.

thyroidectomy: The surgical removal of part or all of the thyroid gland.

thyroxine: The hormone produced by the thyroid gland.

T3: see Triiodothironine or Cytomel.

T4: see Thyroxine.

TMJ: Abbreviation for temporomandibular joint dysfunction.

Total T3: The total T3 measures the concentration of triiodothyonine in the serum. The T3 is increased in almost all cases of hyperthyroidism and usually goes up before the T4 does. Thus the T3 is a more sensitive indicator of hyperthyroidism than the Total T4. In hypothyroidism the T3 is often normal even when the T4 is low. The T3 is decreased during acute illness and starvation, and is affected by several medications including Inderal, steroids and amiodarone. This test measures both bound and free hormone. Only the free hormone is biologically active, but is only 0.5% of the total. Anything which affects thyroid binding globulin (TBG), or albumin will affect the total Triiodothyronine but not the free.

Total T4: The T4 test measures the concentration of Thyroxine in the serum. This includes both bound and free hormone. Only the free hormone, about 0.05% of the total, is biologically active. Anything which affects levels of thyroid binding globulin (TBG), albumin, or thyroid binding prealbumin will affect the total thyroxine but not the free hormone. Estrogens and acute liver disease will increase thyroid binding, while androgens, steroids, chronic liver disease and severe illness can decrease it.

TRH test: Abbreviation for thyrotropin-releasing hormone.

TSH: Thyroid Stimulating Hormone is secreted from the pituitary gland to stimulate the thyroid gland. Once the thyroid gland starts secreting thyroid hormones, these hormones reach the pituitary and decrease the secretion of TSH in a perfect feed-back loop. Normal ranges fall between 0.35 - 5.50.

TSH test: a more sensitive thyroid hormone test which makes the TRH test unnecessary.

Triiodothironine toxicosis: toxicosis , thyroid toxicosis; hyperthyroidism resulting from excessive circulating 3,5,3‚-triiodothyronine.

Tyrosint: a drug; one of the different brands of the thyroid hormone T4 or levothyroxine.

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Last updated: October 23, 2006