Myxedema

Source: Wikipedia, the free encyclopedia.
This article is about skin changes that occur in hypothyroidism. The word myxedema was historically used to refer hypothyroidism in general. For the related medical emergency, see myxedema coma.
Myxedema
Other namesMyxoedema
mucopolysaccharide
SpecialtyEndocrinology

Myxedema (

Hashimoto thyroiditis and other long-standing forms of hypothyroidism
.

Etymology

The word myxedema originates from μύξᾰ, meaning "mucus" or "slimy substance", and οἴδημα for "swelling".

Signs and symptoms

Man with myxedema or severe hypothyroidism showing an expressionless face, puffiness around the eyes and pallor
Additional findings include swelling of the arms and legs and significant ascites.
Woman with myxedema, Bulgaria, 1930s.

Myxedema's characteristic physical sign is

pitting edema.[1]

Myxedema can also occur in the lower leg (pretibial myxedema) and behind the eyes (exophthalmos).

Severe cases, requiring hospitalization can exhibit signs of hypothermia, hypoglycemia, hypotension, respiratory depression, and coma.

Causes

Myxedema is known to occur in various forms of

Graves disease. One of the hallmarks of Grave's disease is pretibial myxedema, myxedema of the lower limb.[2]

Myxedema is more common in women than in men.[3]

Myxedema can occur in:

Pathophysiology

Myxedema describes a specific form of

mucopolysaccharides.[2]
This protein-mucopolysaccharide complex binds water, producing non-pitting boggy edema, in particular around eyes, hands, feet and in the supraclavicular fossae. Myxoedema is responsible for the thickening of the tongue and the laryngeal and pharyngeal mucous membranes, which results in thick slurred speech and hoarseness, both of which are seen commonly in hypothyroidism.

The increased deposition of glycosaminoglycan is not fully understood, however, two mechanisms predominate:

  • thyroid stimulating hormone (TSH) receptor increases the deposition of glycosaminoglycan, which results in an osmotic edema and fluid retention. It is thought that many cells responsible for forming connective tissue react to increases in TSH levels.[6][7]
  • Lymphocyte stimulation. In Graves' thyroid disease, lymphocytes react against the TSH receptor by inappropriately producing thyroid-stimulating immunoglobulin (IgG; type II hypersensitivity). Lymphocytes react not only against thyroid receptors, but also any tissue with cells expressing the receptor. This can lead to tissue damage and scar tissue formation, explaining the deposition of glycosaminoglycans.[8]

Diagnosis

It is often possible to diagnose myxedema on clinical grounds alone. Characteristic symptoms are weakness, cold intolerance, mental and physical slowness, dry skin, typical facies, and hoarse voice. Results of the total serum thyroxine and free thyroxine index tests usually will confirm the diagnosis.[9]

Management

Primary treatment is prompted by the administration of adequate doses of either the thyroid hormone

L-thyroxine given intravenously or by giving liothyronine via a nasogastric tube. It is essential to identify and treat the condition precipitating the coma.[9]

Myxedema coma is rare but often fatal. It occurs most often in elderly women and may be mistaken for one of the chronic debilitating diseases common to this age group.[9]

Though the exact cause of myxedema is still unclear, a wealth of research has demonstrated the importance of iodine.[10] In an important study[11] the researchers showed that in the myxedematous type of cretinism treatment with iodine normalizes thyroid function provided that the treatment is begun early in the postnatal period. If not, the prognosis remains dismal.[10]

History

Myxedema was first treated successfully in 1891 when George Redmayne Murray diagnosed a 46-year-old woman with the disease. He prescribed an extract from sheep thyroid. The patient improved significantly within a few weeks and lived another 28 years while taking the sheep thyroid extract.[12]

References

  1. PMID 35936163
    .
  2. ^
    ISBN 978-1-4377-0314-6.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  3. ISBN 978-1451109061
    .
  4. ^ "Pretibial Myxedema". Archived from the original on 2016-03-04. Retrieved 2009-03-27.
  5. ^ "Hypothyroidism". The Lecturio Medical Concept Library. Retrieved 27 July 2021.
  6. ^ "Fibroblast". Genetics Home Reference. U.S. National Library of Medicine. 2014-05-05. Retrieved 2014-05-10.
  7. ^ "Fibroblasts". Retrieved 16 August 2018.
  8. ^ "Lymphocytes". The Lecturio Medical Concept Library. Retrieved 27 July 2021.
  9. ^
    PMID 624451
    .
  10. ^
    PMID 21760981
    .
  11. PMID 3018564
    .
  12. ^ "Eating Organs to Cure Disease". Tacomed.com. Archived from the original on 6 September 2017. Retrieved 15 June 2017.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Myxedema&oldid=1209483923"