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. 

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 

Causes

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

• Hashimoto’s disease (an autoimmune condition) 
• Congenital hypothyroidism (present at birth) 
• Surgical removal of all or part of the thyroid 
• Radiation therapy
• Inflammation of the thyroid (thyroiditis) 
• Certain medications (e.g., lithium, chemotherapy drugs) 
• Iodine deficiency or excess iodine
• Family history of thyroid disease 
• Pituitary gland and/or hypothalamic disorders

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 

Diagnosis

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:

• Anemia (low iron) 
• Hypoglycemia (low blood sugar) 
• Hyponatremia (low sodium levels) 
• High cholesterol 
• Elevated liver enzymes

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. 

Treatment

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:

• Synthroid, Levoxyl, Unithroid, or Levothroid (levothyroxine) (synthetic T4/thyroid hormone) 
• Glucocorticoid steroids 

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.

Summary 

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.