Myxedema
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| Myxedema | |
|---|---|
| Specialty | Endocrinology  |
Myxedema is a form of hypothyroidism developing in the older child or adult. The clinical manifestations vary with the age of the onset of the deficiency. Clinical features of myxedema are characterized by a slowing of physical and mental activity. The initial symptoms include generalized fatigue, apathy, and mental sluggishness. Speech and intellectual functions become slowed. Patients with myxedema are unenthusiastic, cold intolerant, and frequently overweight. Decreased sympathetic activity results in constipation and decreased sweating. The skin of these patients is often cool and pale. The patients often complain about shortness of breath and decreased exercise capacity. In addition, hypothyroidism promotes atherogenic profile, and serum levels of total cholesterol and low-density lipoprotein (LDL) are increased. Patients with unexplained increase in body weight or hypercholesterolemia should be assessed for potential hypothyroidism. Measurement of serum TSH level is the most screening test for this disorder. [1] Myxedema (BrE: myxoedema) describes a specific form of cutaneous and dermal edema secondary to increased deposition of connective tissue components (like glycosaminoglycans, hyaluronic acid, and other mucopolysaccharides) in subcutaneous tissue as seen in various forms of hypothyroidism and Graves' disease (pretibial myxedema).[2]: 535 It is more common in women than in men. [3]
The word originates from [μύξα,] Error: {{Lang}}: text has italic markup (help) taken from ancient Greek to convey 'mucus' or 'slimy substance' and [ὁίδημα] Error: {{Lang}}: text has italic markup (help) for swelling.
Signs and Symptoms
Clinical features of myxedema are characterized by a slowing of physical and mental activity. The initial symptoms include generalized fatigue, apathy, and mental sluggishness. Speech and intellectual functions become slowed. Patients with myxedema are unenthusiastic, cold intolerant, and frequently overweight. Decreased sympathetic activity results in constipation and decreased sweating. The skin of these patients is often cool and pale. The patients often complain about shortness of breath and decreased exercise capacity. [1]
Treatments
Thyroxine administration. [4]
Variants
- Hyperthyroid myxedema is associated with hyperthyroidism, and typically presents in specific areas (pretibial myxedema and exophthalmos) and is related to high levels of TSH receptor stimulation and/or inflammation mounted against the TSH receptor itself. Myxedema of the lower legs (called pretibial myxedema), can occur in one to four percent of patients with Graves' disease -- a condition that causes hyperthyroidism -- or in patients with hypothyroid myxedema.[5]
- Hypothyroid myxedema is used to describe the clinical syndrome secondary to hypothyroidism. Used in this way, myxedema can be considered the adult counterpart of cretinism.[6]
- Myxedema coma is a condition which can occur with or without myxedema.
Cause
The increased deposition of glycosaminoglycan is not fully understood, however two mechanisms predominate.
- Exophthalmos in particular results from TSH receptor stimulation on fibroblasts behind the eyes which leads to increased glycosaminoglycan deposition. It is thought that many cells responsible for forming connective tissue react to increases in TSH levels. [citation needed]
- Secondarily, in autoimmune thyroid diseases lymphocytes react to the TSH receptor. Thus, in addition to the inflammation within the thyroid, any tissue with cells expressing the TSH receptor will likely experience lymphocytic infiltrates as well. The inflammation can cause tissue damage and scar tissue formation, explaining the deposition of glycosaminoglycans. [citation needed]
The increased deposition of glycosaminoglycans causes an osmotic edema and fluid collection.
Hashimoto's thyroiditis, an autoimmune condition, is the most common cause of myxedema in the United States.[7]
See also
References
- ^ a b Vinay Kumar (2010). Robbins and Cotran Pathologic Basis of Disease. p. 1111. ISBN 978-1-4160-3121-5.
{{cite book}}: Unknown parameter|Publisher=ignored (|publisher=suggested) (help) - ^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
{{cite book}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) - ^ BRS Pathology - A.S. Schneider, P.A. Szanto - 3rd edition - page 314
- ^ Bertram Katzung (2012). Basic and Clinical Pharmacology. pp. 684, 691, 693. ISBN 978-0-07-176402-5.
{{cite book}}: Unknown parameter|Publisher=ignored (|publisher=suggested) (help) - ^ "Pretibial Myxedema", Retrieved on 2009-3-27
- ^ "myxedema" at Dorland's Medical Dictionary
- ^ "Hasihimotos Thyroiditis", Retrieved on 2009-3-27
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