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*[[Thyroid hormone]] plays an important role in cellular [[metabolism]]. | *[[Thyroid hormone]] plays an important role in cellular [[metabolism]]. | ||
*Long-standing [[hypothyroidism]] is associated with reduced [[metabolic rate]] and decreased [[oxygen]] consumption, which affects all [[organ systems]]. | *Long-standing [[hypothyroidism]] is associated with reduced [[metabolic rate]] and decreased [[oxygen]] consumption, which affects all [[organ systems]]. | ||
*Reduced metabolism results in [[hypothermia]]. | *Reduced [[metabolism]] results in [[hypothermia]]. | ||
*Reduced metabolism and decreased oxygen also results in decreased drug metabolism leading to overdosing of medications particularly sedatives, hypnotics, and anesthetic agents; this can precipitate myxedema coma. | *Reduced [[metabolism]] and decreased [[oxygen]] also results in decreased drug metabolism leading to overdosing of [[medications]] particularly [[sedatives]], [[hypnotics]], and [[anesthetic agents]]; this can precipitate myxedema coma. | ||
*Even in severe hypothyroidism a balance of metabolic homeostasis is achieved through adaptive neurovascular mechanisms. However in conditions such as respiratory or urinary tract infections, cardiac, acute myocardial infarction or stroke interfere with this adaptive mechanisms by decreasing the blood volume and ventilation triggering myxedema coma. | *Even in severe [[hypothyroidism]] a balance of metabolic homeostasis is achieved through adaptive neurovascular mechanisms. However in conditions such as [[respiratory]] or [[urinary tract infections]], [[cardiac]], [[acute myocardial infarction]] or [[stroke]] interfere with this adaptive mechanisms by decreasing the [[blood volume]] and [[ventilation]] triggering myxedema coma. | ||
{{familytree/start}}{{familytree | | | | | | | | | A01 | | | | | |A01=[[Hypothyroidism]]}} | {{familytree/start}}{{familytree | | | | | | | | | A01 | | | | | |A01=[[Hypothyroidism]]}} | ||
{{familytree | | | | | | | | | |!| | | | | | | | }} | {{familytree | | | | | | | | | |!| | | | | | | | }} | ||
Revision as of 18:56, 19 October 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
Myxedema coma occurs as a result of long-standing, un-diagnosed, or untreated hypothyroidism and is usually precipitated by a systemic illness. Thyroid hormone plays an important role in celluar metabolism. Long-standing hypothyroidism results in reduced metabolic rate and decreased oxygen consumption, which affects all organ systems. Reduced metabolism and decreased oxygen results in hypothermia and decreased drug metabolism leading to overdosing of medications particularly sedatives, hypnotics, and anesthetic agents and can precipitate myxedema coma.
Pathophysiology
- Myxedema coma occurs as a result of long-standing, undiagnosed, or untreated hypothyroidism.[1][2][3][4]
- Myxedema coma is usually precipitated by a systemic illness.
Triggers
- Myxedema coma can result from any of the causes of hypothyroidism, most commonly chronic autoimmune thyroiditis.
- Myxedema coma can also occur in patients who had thyroidectomy or underwent radioactive iodine therapy for hyperthyroidism.
- Rare causes may include secondary hypothyroidism and medications such as lithium and amiodarone.
Pathogenesis
- Thyroid hormone plays an important role in cellular metabolism.
- Long-standing hypothyroidism is associated with reduced metabolic rate and decreased oxygen consumption, which affects all organ systems.
- Reduced metabolism results in hypothermia.
- Reduced metabolism and decreased oxygen also results in decreased drug metabolism leading to overdosing of medications particularly sedatives, hypnotics, and anesthetic agents; this can precipitate myxedema coma.
- Even in severe hypothyroidism a balance of metabolic homeostasis is achieved through adaptive neurovascular mechanisms. However in conditions such as respiratory or urinary tract infections, cardiac, acute myocardial infarction or stroke interfere with this adaptive mechanisms by decreasing the blood volume and ventilation triggering myxedema coma.
| Hypothyroidism | |||||||||||||||||||||||||||||||||||
| Precipitating Factor | |||||||||||||||||||||||||||||||||||
| ↓T4 | |||||||||||||||||||||||||||||||||||
| ↓ IntracellularT3 | |||||||||||||||||||||||||||||||||||
| Hypothalamus | Respiratory | Cardiovascluar | Renal | ||||||||||||||||||||||||||||||||
| ↓ Thermogenesis | Hypercapnia Hypoxia | ↓ Inotropic Bradycardia | ↓ Volume status | ||||||||||||||||||||||||||||||||
| Hypothermia | Hypoventilation | ↓ Cardiac output ↓ Blood volume | ↓ GFR ↑ ADH | ||||||||||||||||||||||||||||||||
| Alteration of mental state | Cerebral anoxia | ↓Arterial pressure/shock | Hyponatremia Edema | ||||||||||||||||||||||||||||||||
| Myxedema Coma | |||||||||||||||||||||||||||||||||||
The following table summarizes the various effects of reduced thyroid hormone on different organ systems
| Organ System | Effect due to Decreased Thyroid Hormone | Manifestation |
|---|---|---|
| Cardiovascular |
|
|
| Neurologic |
| |
| Pulmonary |
|
|
| Renal |
|
|
| Gastrointestinal |
|
|
| Hematologic |
|
Associated Conditions
Common conditions associated with myxedema coma include:
- Type 1 diabetes
- Addison's disease
- Pernicious anemia
- Vitiligo
- Rheumatoid arthritis
- Premature ovarian failure
References
- ↑ Rizzo L, Mana DL, Bruno OD, Wartofsky L (2017). "[Myxedema coma]". Medicina (B Aires) (in Spanish; Castilian). 77 (4): 321–328. PMID 28825577. Vancouver style error: initials (help)
- ↑ Wall CR (2000). "Myxedema coma: diagnosis and treatment". Am Fam Physician. 62 (11): 2485–90. PMID 11130234.
- ↑ Mathew V, Misgar RA, Ghosh S, Mukhopadhyay P, Roychowdhury P, Pandit K, Mukhopadhyay S, Chowdhury S (2011). "Myxedema coma: a new look into an old crisis". J Thyroid Res. 2011: 493462. doi:10.4061/2011/493462. PMC 3175396. PMID 21941682.
- ↑ Wartofsky L (2006). "Myxedema coma". Endocrinol. Metab. Clin. North Am. 35 (4): 687–98, vii–viii. doi:10.1016/j.ecl.2006.09.003. PMID 17127141.