Alternate Names: Myxedema; Adult hypothyroidism

Causes and Risks:

The thyroid gland is located in the front of the neck just below the larynx. The thyroid gland secretes hormones that control body metabolism. These hormones are thyroxine (T4) and triiodothyronine (T3). T4 and T3 are two different types of thyroid hormone.

The secretion of T3 and T4 by the thyroid is controlled by a system involving the pituitary gland and the hypothalamus in the brain. Since the thyroid gland is regulated by the pituitary gland and the hypothalamus, thyroid disorders may result not only from defects in the gland itself, but also from disruption of the control system. Thyroid disorders caused by overproduction of thyroid hormones are called hyperthyroidism, and underproduction of these hormones is known as hypothyroidism.

Hypothyroidism, or underactivity of the thyroid gland, may cause a variety of symptoms and may affect all body functions. The body’s normal rate of functioning slows, causing mental and physical sluggishness. The symptoms may vary from mild to severe, with the most severe form called myxedema, which is a medical emergency.

The causes may be due to disease of the thyroid gland (primary hypothyroidism) such as Hashimoto’s disease where the body’s immune system attacks the thyroid gland, or from failure of the pituitary gland to secrete a hormone to stimulate the thyroid gland (secondary hypothyroidism). Other causes are congenital defects, surgical removal of the thyroid gland, irradiation of the gland, or inflammatory conditions. Risk factors include being over 50 years old, being female, obesity, thyroid surgery, and exposure of the neck to x-ray or radiation treatments. The incidence is 2 out of 100 people.

Prevention:

There is no prevention for hypothyroidism; however, screening tests in newborns can detect congenital hypothyroidism.

Symptoms:

Early symptoms:

• weakness
• fatigue
• cold intolerance
• constipation
• weight gain (unintentional)
• depression
• joint or muscle pain
• thin, brittle fingernails
• thin and brittle hair
• pale color

Late symptoms:

• slow speech
• dry flaky skin
• thickening of the skin
• puffy face, hands and feet
• decreased taste and smell
• thinning of eyebrows
• hoarseness
• menstrual periods, abnormal

Additional symptoms that may be associated with this disease:

• tongue problems
• swelling, overall
• skin color, patchy
• nipple discharge, abnormal
• muscle spasms (cramps)
• muscle pain
• muscle atrophy
• movement, uncoordinated
• menstruation, absent
• joint stiffness
• hearing loss
• hair, dry
• hair loss
• facial swelling
• ear noise/buzzing
• drowsiness
• breast development in males
• blood pressure, high
• appetite, loss
• ankle, feet, and leg swelling
• short stature
• sutures - separated
• teeth - delayed or absent formation

Signs and Tests:

A physical examination reveals delayed relaxation of muscles during tests of reflexes. Pale, yellow skin, loss of the outer edge of the eyebrows, thin and brittle hair, coarse facial features, brittle nails, firm swelling of the arms and legs, and mental slowing may be noted. Vital signs may reveal slow heart rate, low blood pressure, and low temperature.

A chest X-ray may reveal an enlarged heart.

Laboratory tests to determine thyroid function include:

• T4 test (low)
• T3 resin uptake (low)
• serum TSH (high in primary hypothyroidism, low or low-normal in secondary hypothyroidism)

Additional laboratory abnormalities may include:

• increased cholesterol levels
• increased liver enzymes
• increased serum prolactin
• lowserum sodium
• a complete blood count (CBC) that shows anemia

Treatment:

The purpose of treatment is to replace the deficient thyroid hormone. Levothyroxine is the most commonly used medication, but others are available. The lowest dose effective in relieving symptoms is used. Life-long therapy isneeded as relapses will occur if therapy is stopped. Medication must be continued even when symptoms subside.

After replacement therapy has begun, report any symptoms of increased thyroid activity (hyperthyroidism) such as restlessness, rapid weight loss, and sweating.


Myxedema coma is treated by intravenous thyroid replacement and steroid therapy. Supportive therapy of oxygen, assisted ventilation, fluid replacement, and intensive-care nursing may be indicated.

Prognosis:

With early treatment, return to the normal state is usual. However, relapses will occur if the medication is not continued. Myxedema coma can result in death.

Complications:

Myxedema coma, the most severe form of hypothyroidism, is rare. It may be caused by an infection, illness, exposure to cold, or certain medications in an individual with untreated hypothyroidism. Symptoms and signs of myxedema coma include unresponsiveness, decreased breathing, low blood pressure, low blood sugar, and below normal temperature.

Other complications are heart disease, increased risk of infection, infertility, miscarriage in pregnant women, and pituitary tumors.

Call your health care provider if signs of hypothyroidism (or myxedema) are present.

Call your health care provider if chest pain or rapid heart beat occur, infection occurs, symptoms worsen or do not improve with treatment, or new symptoms develop.