Thyroid dysgenesis

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Thyroid dysgenesis
Other namesThyroid agenesis
CT and scintigraphy of lingular ectopic thyroid.jpg
CT scan and scintigraphy images of lingular ectopic thyroid
Specialty Endocrinology

Thyroid dysgenesis is a cause of congenital hypothyroidism [1] where the thyroid is missing, ectopic, or severely underdeveloped. It should not be confused with iodine deficiency, or with other forms of congenital hypothyroidism, such as thyroid dyshormonogenesis, where the thyroid is present but not functioning correctly.

Contents

Congenital hypothyroidism caused by thyroid dysgenesis can be associated with PAX8. [2]

Ectopic thyroid

An ectopic thyroid, also called accessory thyroid gland, is a form of thyroid dysgenesis in which an entire or parts of the thyroid located in another part of the body than what is the usual case. A completely ectopic thyroid gland may be located anywhere along the path of the descent of the thyroid during its embryological development, although it is most commonly located at the base of the tongue, just posterior to the foramen cecum of the tongue. In this location, an aberrant or ectopic thyroid gland is known as a lingual thyroid. [3] If the thyroid fails to descend to even higher degree, then the resulting final resting point of the thyroid gland may be high in the neck, such as just below the hyoid bone. [3] Parts of ectopic thyroid tissue ("accessory thyroid tissue") can also occur, and arises from remnants of the thyroglossal duct, and may appear anywhere along its original length. [3] Accessory thyroid tissue may be functional, but is generally insufficient for normal function if the main thyroid gland is entirely removed. [3]

Lingual thyroid is 4-7 times more common in females, with symptoms developing during puberty, pregnancy or menopause. Lingual thyroid may be asymptomatic, or give symptoms such as dysphagia (difficulty swallowing), dysphonia (difficulty talking) and dyspnea (difficulty breathing). [4]

Related Research Articles

<span class="mw-page-title-main">Hyperthyroidism</span> Clinical syndrome caused by excessive 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">Hypothyroidism</span> Insufficient production of thyroid hormones by the thyroid gland

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, extreme fatigue, muscle aches, 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.

<span class="mw-page-title-main">Congenital hypothyroidism</span> Thyroid hormone deficiency present at birth

Congenital hypothyroidism (CH) is thyroid hormone deficiency present at birth. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often go unrecognized as a problem. Significant deficiency may cause excessive sleeping, reduced interest in nursing, poor muscle tone, low or hoarse cry, infrequent bowel movements, significant jaundice, and low body temperature.

<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 goiter.

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

A thyroglossal cyst or thyroglossal duct cyst is a fibrous cyst that forms from a persistent thyroglossal duct. Thyroglossal cysts can be defined as an irregular neck mass or a lump which develops from cells and tissues left over after the formation of the thyroid gland during developmental stages.

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

Pendred syndrome is a genetic disorder leading to congenital bilateral sensorineural hearing loss and goitre with euthyroid or mild hypothyroidism. There is no specific treatment, other than supportive measures for the hearing loss and thyroid hormone supplementation in case of hypothyroidism. It is named after Vaughan Pendred (1869–1946), the British doctor who first described the condition in an Irish family living in Durham in 1896. It accounts for 7.5% to 15% of all cases of congenital deafness.

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

Macroglossia is the medical term for an unusually large tongue. Severe enlargement of the tongue can cause cosmetic and functional difficulties in speaking, eating, swallowing and sleeping. Macroglossia is uncommon, and usually occurs in children. There are many causes. Treatment depends upon the exact cause.

<span class="mw-page-title-main">Frenulum of the tongue</span> Small fold of mucous membrane

The frenulumof the tongue, tongue web, lingual frenulum, frenulum linguae, or fraenulum is a small fold of mucous membrane extending from the floor of the mouth to the midline of the underside of the human tongue.

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

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 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.

<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.

The thyroid hormone receptor (TR) is a type of nuclear receptor that is activated by binding thyroid hormone. TRs act as transcription factors, ultimately affecting the regulation of gene transcription and translation. These receptors also have non-genomic effects that lead to second messenger activation, and corresponding cellular response.

<span class="mw-page-title-main">Sodium/iodide cotransporter</span> Mammalian protein found in Homo sapiens

The sodium/iodide cotransporter, also known as the sodium/iodide symporter (NIS), is a protein that in humans is encoded by the SLC5A5 gene. It is a transmembrane glycoprotein with a molecular weight of 87 kDa and 13 transmembrane domains, which transports two sodium cations (Na+) for each iodide anion (I−) into the cell. NIS mediated uptake of iodide into follicular cells of the thyroid gland is the first step in the synthesis of thyroid hormone.

<span class="mw-page-title-main">Young–Simpson syndrome</span> Medical condition

Young–Simpson syndrome (YSS) is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, intellectual disability, and postnatal growth retardation.

<span class="mw-page-title-main">PAX8</span> Mammalian protein found in humans

Paired box gene 8, also known as PAX8, is a protein which in humans is encoded by the PAX8 gene.

<span class="mw-page-title-main">FOXE1</span> Mammalian protein found in Homo sapiens

Forkhead box protein E1 is a protein that in humans is encoded by the FOXE1 gene.

<span class="mw-page-title-main">TSHB</span> Protein-coding gene in the species Homo sapiens

Thyroid stimulating hormone, beta also known as TSHB is a protein which in humans is encoded by the TSHB gene.

<span class="mw-page-title-main">Iodotyrosine deiodinase</span> Protein-coding gene in the species Homo sapiens

Iodotyrosine deiodinase, also known as iodotyrosine dehalogenase 1, is a type of deiodinase enzyme that scavenges iodide by removing it from iodinated tyrosine residues in the thyroid gland. These iodinated tyrosines are produced during thyroid hormone biosynthesis. The iodide that is scavenged by iodotyrosine deiodinase is necessary to again synthesize the thyroid hormones. After synthesis, the thyroid hormones circulate through the body to regulate metabolic rate, protein expression, and body temperature. Iodotyrosine deiodinase is thus necessary to keep levels of both iodide and thyroid hormones in balance.

Bamforth–Lazarus syndrome is a genetic condition that results in thyroid dysgenesis. It is due to recessive mutations in forkhead/winged-helix domain transcription factor. It is associated with FOXE1.

<span class="mw-page-title-main">Hypothyroidism in dogs</span> Medical condition

Hypothyroidism is an endocrine disorder in which the thyroid gland fails to produce sufficient thyroid hormones. Hypothyroidism is one of the most common endocrinopathies in dogs. It is either acquired or congenital.

References

  1. ↑ Castanet M, Park SM, Smith A, et al. (August 2002). "A novel loss-of-function mutation in TTF-2 is associated with congenital hypothyroidism, thyroid agenesis and cleft palate". Hum. Mol. Genet. 11 (17): 2051–9. doi: 10.1093/hmg/11.17.2051 . PMID   12165566.
  2. ↑ Macchia PE, Lapi P, Krude H, et al. (May 1998). "PAX8 mutations associated with congenital hypothyroidism caused by thyroid dysgenesis". Nat. Genet. 19 (1): 83–6. doi:10.1038/ng0598-83. PMID   9590296. S2CID   33957230.
  3. 1 2 3 4 emedicine > Embryology of the Thyroid and Parathyroids > Thyroid Embryology Clinical Correlations By David J Kay and Arlen D Meyers. Updated: Jan 14, 2010
  4. ↑ Bouquot, Brad W. Neville, Douglas D. Damm, Carl M. Allen, Jerry E. (2002). Oral & maxillofacial pathology (2. ed.). Philadelphia: W.B. Saunders. pp. 11–12. ISBN   978-0721690032.{{cite book}}: CS1 maint: multiple names: authors list (link)
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