Most cases of hypothyroidism, or underactive thyroid, are mild. However, hypothyroidism left untreated can result in myxedema.
The most life-threatening complication associated with myxedema is a myxedema coma.
What is a myxedema coma?
When the body experiences an ongoing deficiency of thyroid hormones, there is a heightened risk of a myxedema coma.
A myxedema coma is also known as a myxedema crisis. This serious medical condition occurs when the body can no longer cope with long-term, severely low levels of thyroid hormones.
Although it is rare, a myxedema coma is a medical emergency that requires immediate attention. In some cases, it can result in death.
Despite the name, a myxedema coma does not require the presence of either myxedema (skin changes) or a coma for it to be diagnosed.
According to the American Academy of Family Physicians, the primary sign of myxedema coma is a deterioration of mental state. For example, a person may experience confusion, hallucinations, or disorientation.
Other signs and symptoms of a myxedema coma include:
- high carbon dioxide levels in the blood
- hypothermia, or low body temperature
- labored breathing
- low blood sodium levels
- low oxygen levels in the blood
- shock, or a sudden drop in blood flow
People with severe hypothyroidism may experience the following signs and symptoms:
- feeling cold
- goiter or an enlarged thyroid gland
- low blood pressure
- low heart rate
- swelling of the face
- thickening of the skin, particularly of the lower legs
- thinning hair
- weight gain
Causes and triggers
Potential causes of myxedema include inflammation or removal of the thyroid gland, certain medicines, and pregnancy.
Myxedema is the result of severe hypothyroidism that is undiagnosed or not treated. It is most commonly seen in those with a history of thyroid surgery or radiotherapy.
The causes of hypothyroidism can include:
- Hashimoto's disease, an autoimmune condition and the most common cause of hypothyroidism in the U.S.
- Thyroiditis, or inflammation of the thyroid gland.
- Congenital hypothyroidism, a condition present from birth that is usually screened for in newborns.
- Surgical removal of the thyroid due to thyroid cancer or other conditions.
- Radiation therapy.
- Certain medications.
- Pituitary gland abnormalities caused by surgery, tumors, or medical conditions, such as Sheehan's syndrome.
- An iodine imbalance.
- Pregnancy, with some research estimating that hypothyroidism occurs in 1 out of every 1,600 to 2,000 deliveries.
In rare cases, myxedema may occur in people with normal thyroids but whose pituitary gland or hypothalamus, both of which are part of the brain, fail to send messages correctly to the thyroid gland.
In someone with hypothyroidism, a myxedema coma can be triggered by:
- cold weather
- discontinuing hypothyroid treatment
- hypoglycemia or low blood sugar
- sudden illness, such as a heart attack
- infection, such as pneumonia
- taking certain medications to suppress the central nervous system
- trauma, such as surgery, burns, or accidents
The biggest risk factor for myxedema coma is to have hypothyroidism that is untreated.
Other risk factors include:
- sex - women are more at risk of hypothyroidism and myxedema coma than men
- age - older adults, aged 60 or above, are at greater risk
- stressful or traumatic events
- cold weather
A doctor, usually an endocrinologist, will probably be able to diagnose severe hypothyroidism or myxedema based on a person's symptoms. A diagnosis will be confirmed using blood tests.
Blood tests are used to evaluate levels of:
- T3 (triiodothyronine) and T4 (thyroxine). Low levels of hormones produced by the thyroid can indicate hypothyroidism.
- Thyroid-stimulating hormone (TSH). Produced by the pituitary gland, a high level of TSH suggests hypothyroidism. This is because the pituitary is signaling to the thyroid that more levels of T3 and T4 are needed in the body.
Blood tests may also check for:
- adrenal gland function
- blood cell count
- blood glucose levels
- carbon dioxide levels
- liver function
- oxygen levels
Heart activity may be checked using an ECG (electrocardiogram) and the brain may be looked at with a CT scan. Lung function might also be tested.
As myxedema coma is a medical emergency and life threatening, so it requires immediate treatment, usually in an intensive care unit (ICU).
Treatment options may include thyroid hormone replacement therapy, which will be administered through an IV line.
Doctors will continually monitor the level of consciousness and vital signs of those with myxedema coma.
Vital signs include:
- blood pressure
- body temperature
- pulse rate
Thyroid hormone replacement therapy is administered through a vein, using an intravenous (IV) line.
It may take weeks for a person's thyroid hormones to return to normal levels. Once levels are restored, their symptoms will improve. However, some form of thyroid medication will be necessary for the rest of the person's life.
Other treatments may be given, such as:
- antibiotics for infection
- electrolyte replacement
- glucose supplements for low blood sugar
If doctors do not diagnose myxedema coma swiftly and treat it urgently, it can be fatal. Even with prompt diagnosis and immediate treatment, studies have suggested that between 30 and 60 percent of people die.
Complications that can lead to death include:
- gastrointestinal bleeding
- respiratory failure
A poorer outlook is connected with:
- older age
- persistent low body temperature or hypothermia
- slow heart rate, known as bradycardia
- damage to more than one organ
- poor consciousness
However, once myxedema is under control and the symptoms of myxedema coma have passed, the outlook is good, provided people follow their treatment regimen for the rest of their lives.