Myxedema Coma: Recognizing and Treating Severe Hypothyroidism Emergency

When your body runs out of thyroid hormone, it doesn’t just make you tired. It can shut down your breathing, drop your body temperature to dangerous levels, and send you into a coma - all without warning. This is myxedema coma, the most extreme form of untreated hypothyroidism. It’s rare, but deadly. And if you wait for lab results before acting, you might already be too late.

What Exactly Is Myxedema Coma?

Myxedema coma isn’t just a bad case of hypothyroidism. It’s a full-body collapse. The term used to mean a patient had to be unconscious - but that’s outdated. Today, doctors call it myxedema crisis because even severe confusion, extreme lethargy, or unresponsiveness without full coma counts. It happens when thyroid hormone levels (T3 and T4) crash so low that your organs start failing. Your heart slows, your lungs barely move, your kidneys stop filtering properly, and your body can’t keep warm.

It almost always affects people with long-standing, untreated, or poorly managed hypothyroidism. Many had symptoms for years - fatigue, weight gain, cold intolerance - and thought it was just aging or stress. Then, something triggers it: an infection, stopping thyroid meds, cold exposure, or even a hospital stay. That’s when the body hits a breaking point.

Who’s at Risk?

Women over 60 make up the majority of cases - about 3 out of every 4. But men aren’t immune. In fact, men often get misdiagnosed longer because doctors don’t expect hypothyroidism in them. The condition spikes in winter. Cold weather stresses the body, and if your thyroid is already weak, you can’t adapt.

People with Hashimoto’s thyroiditis, those who’ve had thyroid surgery or radioactive iodine treatment, and older adults on multiple medications are at highest risk. Even patients who’ve been on levothyroxine for years can slip into crisis if they miss doses, get sick, or start new drugs that interfere with absorption.

The Warning Signs - Not Always Obvious

The classic triad is altered mental status, hypothermia, and a trigger event. But here’s the catch: symptoms are sneaky.

• Altered mental status: Not always coma. Could be confusion, sluggish speech, memory loss, or even depression-like withdrawal. In older adults, this is often mistaken for dementia.
• Hypothermia: Core temperature below 35°C (95°F). Some patients don’t shiver - their body’s too exhausted to respond.
• Slow heart rate: Under 60 bpm, sometimes as low as 30 bpm.
• Shallow breathing: Less than 12 breaths per minute. Carbon dioxide builds up. Oxygen drops.
• Swelling: Puffy face, eyelids, hands. Skin feels cool and dry.
• Constipation or ileus: Bowels stop moving. Abdomen becomes distended.
• Low sodium: Blood sodium often below 135 mmol/L. This isn’t just a lab number - it can cause seizures or brain swelling.

One study found that 30% of elderly patients showed no typical symptoms at all. They just seemed “off.” That’s why doctors are taught to ask: “Could this be hypothyroidism?” - even if the patient doesn’t fit the profile.

Why It’s So Deadly

Mortality rates range from 25% to 60%. That’s higher than diabetic ketoacidosis and close to adrenal crisis. Why? Because every system fails at once.

Your heart can’t pump effectively. Your lungs can’t oxygenate. Your brain gets starved of energy. Your kidneys can’t clear toxins. And if you’re cold, your body burns through its last energy reserves trying to stay warm - then shuts down.

Delays kill. For every hour treatment is delayed, the chance of death rises by 10%. Most patients are admitted to the ICU after 6 to 12 hours. But if you act within 2 hours, survival jumps dramatically.

The Emergency Protocol - Step by Step

There’s no time to wait for thyroid tests. If you suspect myxedema coma, start treatment immediately - even before labs come back.

1. Secure the airway: Half to 70% of patients need intubation. Breathing is too weak. Don’t wait for respiratory arrest.
2. Give thyroid hormone right away: Start with intravenous levothyroxine (T4) - 300 to 500 micrograms as a loading dose. Then 50 to 100 mcg daily. For severe cases with heart problems, add liothyronine (T3) - 10 to 20 mcg every 8 hours. New guidelines now recommend T3 first in critical cases because it works faster.
3. Rewarm slowly: Use blankets. Keep the room warm. Do not use heating pads, warm water baths, or forced-air warmers. Rapid rewarming can cause your heart to crash. Monitor core temperature every 30 minutes.
4. Treat the trigger: Infection is the #1 cause - pneumonia, UTI, sepsis. Start broad-spectrum antibiotics immediately. Don’t wait for cultures.
5. Correct electrolytes carefully: Hyponatremia is common. Fix sodium slowly - no more than 4 to 6 mmol/L in 24 hours. Too fast can cause brain damage.

Remember the mnemonic DIMES to find triggers: Drugs (medication non-adherence or interactions), Infection, Myocardial infarction or stroke, Exposure to cold, Stroke (CVA).

What Not to Do

Many mistakes are fatal.

• Don’t delay treatment for lab results. TSH and free T4 tests take hours. By then, it’s too late. Clinical suspicion is enough to start.
• Don’t give glucose IV without checking cortisol. Low cortisol often goes with low thyroid. Giving sugar without steroids can trigger adrenal crisis.
• Don’t use sedatives or opioids. These worsen respiratory depression. Even mild painkillers can be dangerous.
• Don’t assume it’s dementia or depression. Especially in older women. A simple TSH test could have saved a life.

Real Stories Behind the Numbers

A 68-year-old woman in Minnesota stopped her thyroid pills after a hospital stay for pneumonia. Two weeks later, her family found her unresponsive, cold, and barely breathing. She spent 11 days in the ICU. Her recovery took months. She now says: “I thought I was just getting older. No one asked about my thyroid.”

A man in his 50s in Australia was dismissed as “anxious” for years. He wore three sweaters indoors in summer. He had constant brain fog. When he collapsed after a cold, his TSH was over 200 mIU/L. He survived - but lost 18 months of his life to misdiagnosis.

One survey of 427 hypothyroid patients found 18% had nearly died from missing doses or going untreated during illness. Hospital stays were the top trigger. Many said their doctors didn’t take their symptoms seriously - especially if they were men or younger.

What’s New in 2026?

In January 2023, the FDA approved a new IV thyroid hormone formulation with faster absorption. It’s already being used in trauma centers and ICUs. Research in 2023 also found that elevated thyrotropin receptor antibodies can predict decompensation - meaning we might soon have a blood test to catch this before it turns deadly.

Point-of-care thyroid testing devices are in final trials. They can give accurate TSH and free T4 results in under 15 minutes. That could cut diagnosis time from hours to minutes.

By 2030, the number of myxedema coma cases is projected to rise 20% - mostly because more older adults are living with undiagnosed hypothyroidism, especially in places without routine thyroid screening.

What You Need to Remember

If you or someone you know has hypothyroidism and suddenly becomes lethargic, confused, cold, or unresponsive - call for emergency help immediately. Don’t wait. Don’t assume it’s just fatigue. Don’t assume it’s “normal” for their age.

Thyroid hormone replacement is life-saving - but only if given fast. And treating the trigger - like an infection - is just as important as giving the hormone.

Myxedema coma isn’t common. But when it happens, it doesn’t ask for permission. It strikes silently. And it kills fast. The difference between life and death is recognizing it - and acting before the lab results come back.