What Is Myxedema Coma?

Myxedema coma is an extreme complication of hypothyroidism (low thyroid hormone). It’s rare and potentially fatal. The condition is also called myxedema crisis.

Myxedema coma is most common when severe hypothyroidism has gone untreated for a long time. It rarely leads to a coma. Instead, it causes lethargy due to slowed function of multiple systems.

Myxedema Coma Symptoms

Myxedema coma has three major symptoms:

• Altered mental status: You may be lethargic, sleep a lot, and have episodes of reduced consciousness for a few months, then eventually enter a coma.
• Defective temperature regulation (hypothermia): You lose the ability to maintain your body temperature. Exposure to the cold can make your body temperature drop sharply.
• Triggering event: It takes ongoing hypothyroidism plus another event to trigger this crisis. This trigger may be cold exposure, infection, use of certain drugs, trauma, stroke, heart failure, or bleeding in your digestive tract.

Causes

Your thyroid gland makes hormones that regulate homeostasis. That’s the way your body controls automatic things like temperature, digestion, and heart rate.

When thyroid hormones are low, your body adapts and finds other ways to maintain homeostasis. But then, a triggering event strains the body’s resources, and as a result:

• Your body can’t keep up the adaptations. 
• Your core temperature drops. 
• Multiple functions in your body slow down. 

Causes of Hypothyroidism

Lots of things can cause low thyroid levels:

• Hashimoto’s disease (an autoimmune thyroid condition)
• Radiation treatments for cancer
• Some immune system medications
• Medications, including lithium and Pacerone (amiodarone)
• Pregnancy
• Partial or complete thyroid removal (thyroidectomy)

Your levels can also drop if you go off of thyroid medication. Don’t stop taking your medication without talking to your doctor.

Risk Factors

Myxedema coma is most common in the winter. You’re at higher risk if:

• You’re female
• You’re over 60 years old
• You have a history of hypothyroidism
• You’ve had neck surgery or radioactive iodine treatment

Diagnosis

Doctors identify myxedema coma in several ways. A physical exam may show: 

• Low body temperature
• Slow breathing
• Low blood pressure
• Slow heart rate
• Delayed reflexes
• Coarse, dry skin
• Enlarged tongue

Lab tests may reveal:

• Anemia
• Low blood sugar
• Low sodium
• Low cortisol (the stress hormone)
• High cholesterol
• High creatine kinase 
• Low thyroid hormone
• High thyroid-stimulating hormone (TSH)

Treatment

Fast treatment of myxedema coma is crucial. Treatments must address each problem. They may include:

• Thyroid hormone supplements
• A ventilator 
• Blankets for warming (direct heat is discouraged)
• Fluid restriction to increase sodium levels
• Adding blood to increase blood pressure
• Glucose (sugar) for low blood sugar
• Treatment of triggering event, such as antibiotics for infection
• Steroid hormone replacement

You may need other treatments, depending on your symptoms and lab test results.

Prognosis

The prognosis, or outlook, for someone with myxedema coma is poor unless the condition is promptly recognized and treated. The lower the body temperature gets, the more likely the person will die.

Summary

Myxedema coma results from long-term, untreated hypothyroidism plus a triggering event that strains the body’s resources. This causes multiple systems and organs to slow down, leading to lethargy, excessive sleep, and possibly loss of consciousness. The best way to prevent myxedema coma is to have your thyroid condition diagnosed and treated early.

A Word From Verywell

Myxedema coma is a potentially life-threatening complication of hypothyroidism. It’s more likely to happen if your thyroid condition is not managed. If you have signs of hypothyroidism, talk to your doctor about your concerns. Getting diagnosed and treated early can significantly reduce your risk of having myxedema coma. If you or someone you know is having symptoms that could point to myxedema coma, get medical help immediately. The sooner you act, the better the chance of recovery.