Advanced Hypothyroidism in Adults (Myxedema): Signs, Causes, Treatment

Thyroid hormone plays an essential role in regulating metabolism, and a deficiency can disrupt many body functions, including heart rate, metabolism, and body temperature.

Thyroid hormone replacement is an effective treatment that helps restore and balance thyroid hormone levels. If left untreated, hypothyroidism (underactive thyroid) can progressively slow body functions and lead to health issues, including heart disease, weight gain, joint and muscle pain, and depression.

Myxedema is the most advanced form of hypothyroidism. Though rare, it is life-threatening and requires immediate medical attention.

This article explores the symptoms of advanced hypothyroidism (myxedema), its causes, treatment, and outlook for adults with the condition. 

Healthcare provider checking a woman's thyroid gland.

Jose Luis Pelaez Inc / Getty Images

Signs & Symptoms of Advanced Hypothyroidism

Thyroid hormone deficiency progressively slows all body functions. If hypothyroidism is undiagnosed or untreated, symptoms will gradually worsen in severity. Over time, it becomes more difficult for the body to cope with stressors, such as cold weather or infections. 

Signs and symptoms of advanced hypothyroidism can include:

  • Cold intolerance 
  • Constipation 
  • Depression 
  • Enlarged tongue
  • Facial puffiness, especially around the eyes and lips 
  • Goiter (a lump in the neck indicative of an enlarged thyroid gland)
  • Lethargy (fatigue)
  • Low blood pressure
  • Menstrual cycle changes (e.g., failure to menstruate or excessive menstrual bleeding) 
  • Slow heart rate 
  • Thick, swollen skin, especially in the hands and legs
  • Weakness
  • Weight gain

Symptoms of a Myxedema Crisis

If advanced hypothyroidism is left untreated, it can lead to a myxedema crisis, or myxedema coma. When this occurs, the body’s vital organs cannot function normally (e.g., brain, heart, kidneys). Myxedema crisis is life-threatening and requires immediate medical attention.

Myxedema crisis signs and symptoms include:

  • Abdominal swelling 
  • Altered mental state (e.g., confusion, disorientation) 
  • Bradycardia (slowed heart rate) 
  • Decreased mobility 
  • High systolic and low diastolic blood pressure
  • Hypothermia (body temperature below 95.9 degrees Fahrenheit)
  • Low blood sugar
  • Low sodium levels 
  • Seizures
  • Shallow breathing 
  • Slow reflexes 


Hypothyroidism occurs when the thyroid gland produces insufficient amounts of thyroid hormone. Causes of hypothyroidism include:

Advanced hypothyroidism can progress to myxedema if left untreated. Certain situations that put extra stress on a body with too little thyroid hormone can trigger myxedema, including:

  • Exposure to cold temperatures 
  • Infection
  • Certain medications (e.g., sedatives, analgesics, diuretics, tranquilizers) 
  • Trauma/injury 
  • Heart failure
  • Gastrointestinal bleeding 

Risk Factors for Advanced Hypothyroidism

Risk factors for advanced hypothyroidism include:

  • Being over age 60
  • Assigned female sex at birth
  • History of neck surgery 
  • Previous radiation treatment


Healthcare providers look for signs and symptoms of advanced hypothyroidism (e.g., altered mental state, hypothermia). Your healthcare provider will order blood tests to check thyroid hormone levels to confirm the diagnosis. 

Blood tests to diagnose advanced hypothyroidism include:

  • Free T4 index: Measures how much thyroxine (T4) the thyroid produces 
  • Total T3 levels: Measures how much triiodothyronine (T3) the thyroid produces
  • Serum TSH: Measures how much thyroid-stimulating hormone the pituitary gland produces 

Additional lab tests may be ordered to confirm myxedema crisis. Your healthcare provider will check for the following:

Healthcare providers will also look for physical signs of advanced hypothyroidism, such as dry skin, sparse/brittle hair, goiter, slow breathing, low blood pressure, heart rate, and body temperature. 


Myxedema is a medical emergency that requires rapid treatment. If your healthcare provider suspects a myxedema crisis, you will be admitted to the hospital's intensive care unit (ICU), where thyroid hormone replacement therapy will begin immediately. 

Medications administered intravenously (in the vein) to treat myxedema crisis include:

Your condition will be carefully monitored while in the hospital to ensure your vital organs and body functions are stable. Additional treatments will be provided as needed until you are well enough to go home.

Outlook for Adults With Advanced Hypothyroidism

Thyroid hormone replacement therapy is an effective treatment for advanced hypothyroidism. Lifelong treatment is required, and it’s important to continue taking your medication as prescribed. 

If advanced hypothyroidism is untreated, it can lead to severe health complications and death. Myxedema crisis requires immediate treatment and hospitalization. Mortality rates range between 30% to 60% for those who receive early diagnosis and treatment. Older adults (aged 60 and above) are at a higher risk of death.


Advanced hypothyroidism occurs when hypothyroidism has gone undiagnosed or untreated. Without appropriate treatment, advanced hypothyroidism can progress to myxedema crisis, a medical emergency often triggered by a stressful event, such as cold exposure, infection, or surgery.

Myxedema requires emergency medical care for diagnosis and immediate thyroid hormone replacement therapy. Hospitalization in the intensive care unit is needed to monitor the function of vital organs and body processes. Myxedema crisis has high mortality rates ranging between 30% to 60%, but immediate medical care can help increase survival rates.

A Word From Verywell

Talk to your healthcare provider if you have symptoms of advanced hypothyroidism (e.g., lethargy, puffy face, cold intolerance). Advanced hypothyroidism in adulthood is highly treatable. Lifelong treatment with thyroid hormone replacement therapy can help you feel better and live well.  

Frequently Asked Questions

  • What can make hypothyroidism worse?

    Stopping thyroid hormone replacement therapy or skipping doses can worsen hypothyroidism. Taking too much iodine and eating soy products (e.g., soy milk and edamame) can also worsen hypothyroidism.

  • Is hypothyroidism fatal if left untreated?

    Untreated hypothyroidism can lead to serious health complications, including heart problems, infertility, and myxedema crisis. Myxedema crisis is associated with heart failure, seizures, coma, and death.

  • What is the most severe form of hypothyroidism?

    Myxedema crisis, often called myxedema coma, is the most severe form of hypothyroidism. Myxedema crisis occurs when the body functions slow so significantly that it becomes life-threatening. Myxedema crisis requires immediate medical care.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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