Poorly controlled hypothyroidism Acute precipitant Myxedema Coma

• Etiologies of hypothyroidism include primary, secondary, or tertiary causes.

• Primary hypothyroidism (disease of the thyroid gland) accounts for 95% of hypothyroidism. Diseases include Hashimoto's thyoiditis most commonly, iatrogenic causes (post-radiation, post-surgical, anti-thyroid medications), congenital abnormalities, enzymatic defects, neoplasms, or infections

• Secondary hypothyroidism (disease of the pituitary gland) accounts for 4% of hypothyroidism. Diseases include pituitary tumors, infiltrative diseases (sarcoid), infarction, hemorrhage, or trauma.

• Tertiary hypothyroidism (disease of the hypothalmus) accounts for <1% of hy-pothyroidism. Etiologies include injury, infarction, infiltration or hemorrhage.

• Acute precipitants of myxedema coma are diverse. They include infection most commonly, environmental (prolonged cold exposure), cardiac (ischemia, CHF), pulmonary diseases, metabolic disease, trauma, surgery, or medications.

• The incidence is greater in women, the majority are elderly (half are between the ages of 50 and 70).

• Before the advent of thyroid hormone replacement, the mortality rate approached 100%. Even with treatment, the mortality may be as high as 50%.

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