thyroid gland
Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
gland
[gland]an aggregation of cells specialized to secrete or excrete materials not related to their ordinary metabolic needs. Glands are divided into two main groups, endocrine and exocrine. adj., adj glan´dular.
The endocrine glands, or ductless glands, discharge their secretions (hormones) directly into the blood; they include the adrenal, pituitary, thyroid, and parathyroid glands, the islands of Langerhans in the pancreas, the gonads, the thymus, and the pineal body. The exocrine glands discharge through ducts opening on an external or internal surface of the body; they include the salivary, sebaceous, and sweat glands, the liver, the gastric glands, the pancreas, the intestinal, mammary, and lacrimal glands, and the prostate. The lymph nodes are sometimes called lymph glands but are not glands in the usual sense.
The endocrine glands, or ductless glands, discharge their secretions (hormones) directly into the blood; they include the adrenal, pituitary, thyroid, and parathyroid glands, the islands of Langerhans in the pancreas, the gonads, the thymus, and the pineal body. The exocrine glands discharge through ducts opening on an external or internal surface of the body; they include the salivary, sebaceous, and sweat glands, the liver, the gastric glands, the pancreas, the intestinal, mammary, and lacrimal glands, and the prostate. The lymph nodes are sometimes called lymph glands but are not glands in the usual sense.
Classification of glands according to mode of secretion. From Applegate, 2000.
acinous gland one made up of one or more acini (oval or spherical sacs).
adrenal gland see adrenal gland.
apocrine gland one whose discharged secretion contains part of the secreting cells.
areolar g's Montgomery's glands.
axillary g's lymph nodes in the axilla.
Bartholin g's two small mucus-secreting glands, one on each side in the lower pole of the labium majus and connected to the surface by a duct lined with transitional cells, which opens just external to the hymenal ring. Their exact function is not clear but they are believed to secrete mucus to moisten the vestibule during sexual excitement. Called also major vestibular glands.
Bowman's g's olfactory glands.
bronchial g's seromucous glands in the mucosa and submucosa of the bronchial walls.
Brunner's g's glands in the submucosa of the duodenum that secrete intestinal juice; called also duodenal glands.
buccal g's seromucous glands on the inner surface of the cheeks; called also genal glands.
bulbocavernous g's (bulbourethral g's) two glands embedded in the substance of the sphincter of the male urethra, posterior to the membranous part of the urethra; their secretion lubricates the urethra; called also Cowper's glands.
cardiac g's mucus-secreting glands of the cardiac part (cardia) of the stomach.
celiac g's lymph nodes anterior to the abdominal aorta.
ceruminous g's cerumin-secreting glands in the skin of the external auditory canal.
cervical g's
1. the lymph nodes of the neck.
2. compound clefts in the wall of the uterine cervix.
ciliary g's sweat glands that have become arrested in their development, situated at the edges of the eyelids; called also Moll's glands.
circumanal g's specialized sweat and sebaceous glands around the anus; called also Gay's glands.
Cobelli's g's mucous glands in the esophageal mucosa just above the cardia.
coccygeal gland glomus coccygeum.
compound gland one made up of a number of smaller units whose excretory ducts combine to form ducts of progressively higher order.
Cowper's g's bulbourethral glands.
ductless g's endocrine glands.
duodenal g's Brunner's glands.
Ebner's g's serous glands at the back of the tongue near the taste buds.
eccrine gland one of the ordinary or simple sweat glands, which are of the merocrine type.
endocrine g's see endocrine glands.
exocrine g's glands that discharge their secretions through ducts opening on internal or external surfaces of the body; see gland.
fundic g's (fundus g's) numerous tubular glands in the mucosa of the fundus and body of the stomach that contain the cells that produce acid and pepsin.
gastric g's the secreting glands of the stomach, including the fundic, cardiac, and pyloric glands.
Gay's g's circumanal glands.
genal g's buccal glands.
glossopalatine g's mucous glands at the posterior end of the smaller sublingual glands.
haversian g's synovial villi.
holocrine gland one whose discharged secretion contains the entire secreting cells.
intestinal g's straight tubular glands in the mucous membrane of the intestines, in the small intestine opening between the bases of the villi, and containing argentaffin cells. Called also crypts or glands of Lieberkühn.
jugular gland a lymph node behind the clavicular insertion of the sternocleidomastoid muscle.
Krause's gland an accessory lacrimal gland deep in the conjunctival connective tissue, mainly near the upper fornix.
lacrimal g's the glands that secrete tears; see also lacrimal apparatus.
g's of Lieberkühn intestinal glands.
lingual g's the seromucous glands on the surface of the tongue.
lingual g's, anterior seromucous glands near the apex of the tongue.
Littre's g's
1. preputial glands.
2. the male urethral glands.
lymph gland lymph node.
major vestibular g's Bartholin glands.
mammary gland a specialized gland of the skin of female mammals, which secretes milk for the nourishment of their young; it exists in a rudimentary state in the male. See also breast.
meibomian g's sebaceous follicles between the cartilage and conjunctiva of the eyelids. Called also tarsal glands.
merocrine gland one whose discharged secretion contains no part of the secreting cells.
mixed g's
1. seromucous glands.
2. glands that have both exocrine and endocrine portions.
Moll's g's ciliary glands.
Montgomery's g's sebaceous glands in the mammary areola; called also areolar glands.
mucous g's glands that secrete mucus.
olfactory g's small mucous glands in the olfactory mucosa; called also Bowman's glands.
parathyroid g's see parathyroid glands.
parotid g's see parotid glands.
peptic g's gastric glands that secrete pepsin.
pineal gland pineal body.
pituitary gland see pituitary gland.
preputial g's small sebaceous glands of the corona of the penis and the inner surface of the prepuce, which secrete smegma; called also Littre's glands and Tyson's glands.
prostate gland prostate.
pyloric g's the mucin-secreting glands of the pyloric part of the stomach.
salivary g's see salivary glands.
sebaceous gland a type of holocrine gland of the corium that secretes an oily material (sebum) into the hair follicles.
Glands: The relationship of the hair follicle, eccrine and apocrine sweat glands and sebaceous glands. From Copstead, 1995.
sentinel gland an enlarged lymph node, considered to be pathognomonic of some pathologic condition elsewhere.
seromucous g's glands that are both serous and mucous.
serous gland a gland that secretes a watery albuminous material, commonly but not always containing enzymes.
sex gland (sexual gland) gonad.
simple gland one with a nonbranching duct.
Skene's g's the largest of the female urethral glands, which open into the urethral orifice; they are regarded as homologous with the prostate. Called also paraurethral ducts.
solitary g's solitary follicles.
sublingual gland a salivary gland on either side under the tongue.
submandibular gland (submaxillary gland) a salivary gland on the inner side of each ramus of the mandible.
sudoriferous gland (sudoriparous gland) sweat gland.
suprarenal gland adrenal gland.
sweat gland see sweat gland.
target gland any gland affected by a secretion or other stimulus from another gland, such as those affected by the secretions of the pituitary gland.
tarsal g's meibomian glands.
thymus gland thymus.
thyroid gland see thyroid gland.
tubular gland any gland made up of or containing a tubule or tubules.
Tyson's g's preputial glands.
unicellular gland a single cell that functions as a gland, e.g., a goblet cell.
urethral g's mucous glands in the wall of the urethra; in the male, called also Littre's glands.
uterine g's simple tubular glands found throughout the thickness and extent of the endometrium; they become enlarged during the premenstrual period.
vesical g's mucous glands sometimes found in the wall of the urinary bladder, especially in the area of the trigone.
vulvovaginal g's Bartholin's glands.
Waldeyer's g's glands in the attached edge of the eyelid.
Weber's g's the tubular mucous glands of the tongue.
thyroid
[thi´roid]1. the thyroid gland.
2. pertaining to the thyroid gland.
3. scutiform.
4. a preparation of thyroid gland from domesticated food animals, containing levothyroxine and liothyronine and used as replacement therapy in the diagnosis and treatment of hypothyroidism and the prevention and treatment of goiter and thyroid carcinoma; administered orally.
thyroid crisis a sudden and dangerous increase of the symptoms of thyrotoxicosis, seen in patients with severe hyperthyroidism or in the period immediately following a thyroidectomy. (However, good postoperative care and the use of radioiodine ablation techniques have greatly reduced the incidence of this once common postoperative complication.) Called also thyroid or thyrotoxic storm.
Thyroid crisis is a serious event that can be fatal if not brought under control. All of the body processes are accelerated to dangerously high levels. The pulse may rise to 200 beats per minute, and there is concurrent rise in the respiratory rate. The temperature control center loses control, bringing about a rapid and steady increase in body temperature. Pulmonary edema and congestive heart failure can also occur.
Treatment is aimed at correction of the hyperthyroidism, control of the symptoms, and prevention of further crisis by treating the underlying cause. Medications are employed to block synthesis of thyroid hormones, block their release, and inhibit conversion of triiodothyronine to thyroxine. plasmapheresis. plasma exchange, or hemodialysis may be necessary to remove the hormones from the circulation.
Supportive care includes administration of oxygen and measures to control hyperthermia, such as the use of ice packs or a hyperthermia blanket. Intravenous hydration is important to prevent shock. The use of glucocorticoids is associated with improved survival rates. propranolol, sympatholytics, and guanethidine are often used, as well as other medications that treat symptoms.
Thyroid crisis is a serious event that can be fatal if not brought under control. All of the body processes are accelerated to dangerously high levels. The pulse may rise to 200 beats per minute, and there is concurrent rise in the respiratory rate. The temperature control center loses control, bringing about a rapid and steady increase in body temperature. Pulmonary edema and congestive heart failure can also occur.
Treatment is aimed at correction of the hyperthyroidism, control of the symptoms, and prevention of further crisis by treating the underlying cause. Medications are employed to block synthesis of thyroid hormones, block their release, and inhibit conversion of triiodothyronine to thyroxine. plasmapheresis. plasma exchange, or hemodialysis may be necessary to remove the hormones from the circulation.
Supportive care includes administration of oxygen and measures to control hyperthermia, such as the use of ice packs or a hyperthermia blanket. Intravenous hydration is important to prevent shock. The use of glucocorticoids is associated with improved survival rates. propranolol, sympatholytics, and guanethidine are often used, as well as other medications that treat symptoms.
thyroid function test a test of the functioning of the thyroid gland, such as its proper production of thyroid hormones. See radioiodineuptake test, thyroid-stimulating hormone test, thyrotropin-releasing hormone test, and triiodothyronine resin uptake test.
thyroid gland the largest of the endocrine glands, consisting of two lateral lobes connected by an isthmus; a third pyramidal lobe sometimes extends up from the isthmus. The thyroid gland is located in the front and sides of the neck just below the thyroid cartilage and produces hormones that are vital in maintaining normal growth and metabolism (see thyroid hormones). It also serves as a storehouse for iodine.
Diagnostic tests for thyroid disorders include radioimmunoassay for T3, T4, and thyroid-stimulating hormone (TSH), free thyroxine serum concentration, and free thyroxine index (FTI). These and other thyroid function tests can be distorted by preparations and foods containing iodine, and by oral contraceptives, phenytoin (Dilantin), and several other drugs. The thyroid scan is useful in detecting nodules and active thyroid tissue and, combined with radioactive iodine uptake, measures the ability of the thyroid gland to take in ingested iodine.
Persons who received radiation to the head and neck as children are at higher than normal risk for development of thyroid abnormalities. Of these disorders about one-third are carcinomas of the thyroid. Other problems related to radiation early in life include adenomas and other malignant and benign tumors, hypo- and hyperthyroidism, and thyroiditis. The American Thyroid Association suggests periodic laboratory testing and physical assessment of persons at high risk in order to detect these abnormalities when they are more amenable to treatment.
Diagnostic tests for thyroid disorders include radioimmunoassay for T3, T4, and thyroid-stimulating hormone (TSH), free thyroxine serum concentration, and free thyroxine index (FTI). These and other thyroid function tests can be distorted by preparations and foods containing iodine, and by oral contraceptives, phenytoin (Dilantin), and several other drugs. The thyroid scan is useful in detecting nodules and active thyroid tissue and, combined with radioactive iodine uptake, measures the ability of the thyroid gland to take in ingested iodine.
Persons who received radiation to the head and neck as children are at higher than normal risk for development of thyroid abnormalities. Of these disorders about one-third are carcinomas of the thyroid. Other problems related to radiation early in life include adenomas and other malignant and benign tumors, hypo- and hyperthyroidism, and thyroiditis. The American Thyroid Association suggests periodic laboratory testing and physical assessment of persons at high risk in order to detect these abnormalities when they are more amenable to treatment.
Thyroid gland.
thyroid hormones iodothyronines secreted by the thyroid gland, principally thyroxine (tetraiodothyronine or T4) and triiodothyronine (T3). The serum level of T4 is normally 45 to 50 times the level of T3. However, T3 is several times more active than T4, and most T3 is produced by metabolism of T4 in peripheral tissues. The pharmaceutical names for T4 and T3 are levothyroxine and liothyronine, respectively. Thyroid hormones influence many metabolic processes. They stimulate the cellular production of heat; stimulate protein synthesis; regulate many aspects of carbohydrate metabolism; stimulate lipid synthesis, mobilization, and degradation; stimulate the synthesis of coenzymes from vitamins; and may affect the response of tissues to epinephrine and norepinephrine.
Secretion of thyroid hormones is regulated by the hypothalamus-pituitary-thyroid control system. Internal environmental conditions, such as low thyroid hormone and norepinephrine serum levels, or external factors, such as cold and stress, activate the hypothalamus, which secretes thyrotropin-releasing hormone (TRH). This hormone acts on the pituitary gland and brings about the release of thyroid-stimulating hormone (TSH). The TSH then stimulates the release of thyroid hormones such as T3 and T4 from the thyroid gland. When sufficient levels of serum thyroxine and other thyroid hormones have been reached, there is negative feedback to the hypothalamus and TRH is no longer secreted. See also hypothyroidism and hyperthyroidism.
Secretion of thyroid hormones is regulated by the hypothalamus-pituitary-thyroid control system. Internal environmental conditions, such as low thyroid hormone and norepinephrine serum levels, or external factors, such as cold and stress, activate the hypothalamus, which secretes thyrotropin-releasing hormone (TRH). This hormone acts on the pituitary gland and brings about the release of thyroid-stimulating hormone (TSH). The TSH then stimulates the release of thyroid hormones such as T3 and T4 from the thyroid gland. When sufficient levels of serum thyroxine and other thyroid hormones have been reached, there is negative feedback to the hypothalamus and TRH is no longer secreted. See also hypothyroidism and hyperthyroidism.
thyroid-stimulating hormone test a thyroid function test in which thyrotropin (thyroid-stimulating hormone) is administered intramuscularly and the thyroid gland is monitored over time with scintiscanning or radioimmunoassays for a response or areas of decreased responsiveness. Called also TSH test and TSH stimulation test.
thy·roid gland
[TA]an endocrine (ductless) gland consisting of irregularly spheroid follicles, lying in front and to the sides of the upper part of the trachea and lower part of the larynx and of horseshoe shape, with two lateral lobes connected by a narrow central portion, the isthmus; and occasionally an elongated offshoot, the pyramidal lobe, which passes upward from the isthmus in front of the larynx. It is supplied by branches from the external carotid and subclavian arteries, and its nerves are derived from the middle cervical and cervicothoracic ganglia of the sympathetic system. It secretes thyroid hormone and calcitonin.
thyroid gland
n.
A two-lobed endocrine gland found in all vertebrates, located in front of and on either side of the trachea in humans, and producing various hormones, such as triiodothyronine and calcitonin.
thyroid gland
Etymology: Gk, thyreos, shield, eidos, form
a highly vascular organ at the front of the neck, usually weighing about 30 g, consisting of bilateral lobes connected in the middle by a narrow isthmus. It is slightly heavier in women than in men and enlarges during pregnancy. The majority of the thyroid gland secretes the hormones thyroxin and triiodothyronine, and other clusters of cells produce the hormone calcitonin. These hormones are secreted directly into the blood; thus the thyroid is part of the endocrine system of ductless glands. It is essential to normal body growth in infancy and childhood, and its removal greatly reduces the oxidative processes of the body, producing a lower metabolic rate characteristic of hypothyroidism. The thyroid gland is activated by the pituitary thyrotrophic hormone and requires iodine to elaborate thyroxine. Also called thyroid. Compare parathyroid gland.
)
Thyroid gland
thy·roid gland
(thī'royd gland) [TA]An endocrine gland, consisting of irregularly spheroid follicles, lying in front and to the sides of the upper part of the trachea, of horseshoe shape, with two lateral lobes connected by a narrow central portion, the isthmus; occasionally an elongated offshoot, the pyramidal lobe, passes upward from the isthmus in front of the trachea. It is supplied by branches from the external carotid and subclavian arteries, and its nerves are derived from the middle cervical and cervicothoracic ganglia of the sympathetic system. It secretes thyroid hormone and calcitonin.
)
THYROID GLAND
thyroid gland
A large endocrine gland located in the center of the base of the neck. The gland is composed of two lobes, one on each side of the trachea, and an isthmus of tissue connecting the lower two thirds of each lobe. The isthmus is usually located at the level of the second to third tracheal rings. The whole gland is surrounded by a thin fibrous capsule attached in back to the cricoid cartilage and the first few tracheal rings. The lobes of the thyroid lie under the sternothyroid and sternohyoid muscles. The thyroid is filled with capillary networks (supplied by the superior and inferior thyroid arteries) that surround the many spherical units (follicles) packed inside the gland. Thyroid follicles consist of a ring of follicular cells surrounding a space filled with a clear colloid (a mixture of thyroglobulin proteins and iodine), from which the thyroid hormones (thyroxine and related molecules) are synthesized. These hormones regulate the rate of cellular metabolism throughout the body. All the steps in synthesizing and releasing thyroid hormones are stimulated by thyroid-stimulating hormone (TSH) secreted by the pituitary gland. Another class of thyroid cells, the parafollicular or C cells, is found outside the follicles; C cells secrete calcitonin, a calcium-lowering hormone.
See: illustrationSee also: gland
thyroid gland
An ENDOCRINE GLAND, situated in the neck like a bow tie across the front of the upper part of the windpipe (trachea). The gland secretes hormones that act directly on almost all the cells in the body to control the rate of their METABOLISM.thyroid gland
a large endocrine organ situated in the region of the neck which produces THYROXINE, a hormone that contains iodine obtained from the diet. Thyroxine controls BASAL METABOLIC RATE (BMR), and also controls metamorphosis in amphibians. Undersecretion during development causes hypothyroidism (reduced physical and mental development) leading to CRETINISM in subadults. In the adult stage MYXOEDEMA results, and this gives rise to general slowness of thought and action, coarse skin and fatness. Overproduction, (hyperthyroidism) causes exophthalmic goitre, where the thyroid, and thus the neck, swells and the eyeballs protrude. Those so affected become restless and overactive, lose weight and have an accelerated heart rate. Deficiency or excess of iodine in the diet causes malfunction of the thyroid gland. A deficiency occurs naturally in, for example, parts of Derbyshire, where the symptoms are known as Derbyshire Neck.Thyroid gland
A butterfly-shaped gland in front and to the sides of the upper part of the windpipe; influences body processes like growth, development, reproduction, and metabolism.
Mentioned in: Thyroid Function Tests
thy·roid gland
(thī'royd gland) [TA]Endocrine (ductless) gland consisting of irregularly spheroid follicles, lying in front and to sides of upper part of trachea and lower part of larynx and of horseshoe shape, with two lateral lobes connected by a narrow central portion, the isthmus; secretes thyroid hormone and calcitonin.
thyroid
1. resembling a shield.
2. the thyroid gland (see below) secreting thyroid hormones (see below).
3. a pharmaceutical preparation of cleaned, dried, powdered thyroid gland, obtained from those domesticated animals used for food by humans.
accessory thyroid
an additional thyroid located anywhere from the larynx to diaphragm, e.g. intrapericordial aorta; may be sufficient to supply the patient's need of thyroid hormone. Most common in dogs.
thyroid C cell
see c cell.
thyroid cartilage
the shield-shaped cartilage of the larynx.
thyroid diverticulum
primordium of the thyroid gland; appears as an outgrowth of the foregut between the first two pharyngeal pouches. This tube of epithelial cells grows ventrally into mesenchyme; the tube becomes the thyroglossal duct, the tip divides into two lobes, the thyroid glands.
thyroid dysfunction
ectopic thyroid
migration of thyroid diverticulum tissue to aberrant sites occurs, e.g. thyroid tissue in the thymus. These cause no apparent abnormality.
thyroid extract
a pharmaceutical substance derived from thyroid glands, used in the treatment of hypothyroidism. See thyroid (3) (above).
thyroid function tests
used to assess the functional capacity of the thyroid glands; most commonly employed in dogs and cats. Include plasma T4, plasma T3, free T4 radioiodine uptake, and TSH response tests.
thyroid gland
the largest of the endocrine glands, situated in the neck caudal to the larynx. It produces hormones (see below) that are vital in maintaining normal growth and metabolism. It also serves as a storehouse for iodine.
)
Microscopic appearance of the thyroid gland. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000
thyroid hormones
iodothyronines secreted by the thyroid gland, principally thyroxine (tetraiodothyronine, T4) and tri-iodothyronine (T3); derived from iodination of tyrosyl residues in thyroglobulin. The pharmaceutical names for T4 and T3 are levothyroxine and liothyronine, respectively. Regulate basal metabolic rate.
thyroid parafollicular cell
see c cell.
thyroid radioiodine uptake
used as a thyroid function test but superseded these days by estimates of T4 (thyroxine).
thyroid-stimulating hormone (TSH)
see thyrotropin.
thyroid tumor
mostly follicular adenomas in old-aged dogs, cats and horses; papillary adenomas are rare.
Patient discussion about thyroid gland
Q. Anyone know if there is a connection between Fibromyalgia and your Thyroid gland? I have Fibromyalgia and I read that if your diagnosed with this you can have Thyroid problems also. If anyone knows out there please inform me. Many thanks.
A. Below is an interesting article on the subject. A significant percentage of the estimated 20 million people with hypothyroidism end up also being diagnosed with fibromyalgia. Some experts believe that like most cases of hypothyroidism, fibromyalgia is also autoimmune in nature. Others believe that fibromyalgia may be one manifestation of an under active metabolism – hypometabolism – and is therefore one variation on thyroid dysfunction.
http://thyroid.about.com/cs/fibromyalgiacfs/a/fibrothyroid.htm
http://thyroid.about.com/cs/fibromyalgiacfs/a/fibrothyroid.htm
Q. Is there any natural herb for a sluggish thyroid My uncle is suffering with thyroid for the past 8 months and the treatment he underwent is not successful. Is there any natural herb for a sluggish thyroid?
A. first of all the thyroid gland is situated in the front of the neck, just below the larynx(voice box)it consist of two lobes,one one each side of the trachea(windpipe)joined by a narrower portion of tissue called the isthmus---the thyroid grand produces hormones that regulate metabolism(the chemical activitie in cells that release energy from nutrients or uses energy to create other substances,such as proteins)the thyroid gland regulates the level of calcium in the body.insufficient thyroid hormones prduction is known as hypothyroidism(sluggish thyroid)symtoms include tirednes/dry skin/hair loss/weight gain/constipation/and sensitivity to cold.--because iodine is necessary for the production of thyroid hormones/calcium-ASk your DR before trying natural meds-because they ma interfere with what your uncle is taking now?--and you need to find out from your DR WHY is his thyroid sluggish--mrfoot56--peace
Q. I was told to have my thyroid test and now after the result they have told me to go for MRI I am 23 years old lady……I was told to have my thyroid test and now after the result they have told me to go for MRI……..and I know one of my friend had same type of symptoms and after thyroid test she was on her medicines and now she is well…they say it may be fibromyalgia or sclerosis …why they want me to go for MRI…..there seems to be something serious?
A. i think the MRI is to detect any signs of sclerosis. they try to get a differential diagnosis so they look for sclerosis or any other pathological sign. they didn't find anything in the Thyroid?
More discussions about thyroid gland