Patient Education - Endocrine Encyclopedia
Endocrine Surgery Encyclopedia
 Definition:
Hypothyroidism is a condition in which the thyroid gland fails to produce enough
thyroid hormone.
Alternative Names: Myxedema; Adult hypothyroidism
Causes, incidence,
and risk factors:
The thyroid gland, located in the front of the neck just below the larynx, secretes
hormones that control metabolism. These hormones are thyroxine (T4) and triiodothyronine
(T3).
The secretion of T3 and T4 is controlled by the pituitary gland and the hypothalamus,
which is part of the brain. Thyroid disorders may result not only from defects in
the thyroid gland itself, but also from abnormalities of the pituitary or hypothalamus.
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. The most severe form, called myxedema coma, is a medical emergency.
The most common cause of hypothyroidism is Hashimoto's thyroiditis, a disease
of the thyroid gland where the body's immune system attacks the gland. Failure of
the pituitary gland to secrete a hormone to stimulate the thyroid gland (secondary
hypothyroidism) is a less common cause of hypothyroidism. Other causes include congenital
(birth) defects, surgical removal of the thyroid gland, irradiation of the gland,
or inflammatory conditions.
Risk factors include age over 50 years, female gender, obesity, thyroid surgery,
and exposure of the neck to X-ray or radiation treatments.
Symptoms:
Early symptoms:
- Weakness
- Fatigue
- Cold intolerance
- Constipation
- Weight gain (unintentional)
- Depression
- Joint or muscle pain
- Thin, brittle fingernails
- Thin and brittle hair
- Paleness
Late symptoms:
- Slow speech
- Dry flaky skin
- Thickening of the skin
- Puffy face, hands and feet
- Decreased taste and smell
- Thinning of eyebrows
- Hoarseness
- Abnormal menstrual periods
Additional symptoms that may be associated with this disease:
- Overall swelling
- Muscle spasms (cramps)
- Muscle pain
- Muscle atrophy
- Uncoordinated movement
- Absent menstruation
- Joint stiffness
- Dry hair
- Hair loss
- Drowsiness
- Appetite loss
- Ankle, feet, and leg swelling
- Short stature
- Separated sutures
- Delayed formation or absence of teeth
Signs and tests:
A physical examination reveals delayed relaxation of muscles during tests of reflexes.
Other findings may include pale, yellow skin, thin and brittle hair, coarse facial
features, brittle nails, firm swelling of the arms and legs, and mental slowing.
Vital signs may show slow heart rate, low blood pressure, and low temperature.
A chest x-ray may show an enlarged heart.
Laboratory tests to determine thyroid function include:
- T4 test (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
- Low serum 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. The lowest dose effective in relieving symptoms
and normalizing the TSH is used. Life-long therapy is needed. Medication must be
continued even when symptoms subside. Thyroid hormone levels should be monitored
yearly after a stable dose of medication is determined.
After replacement therapy has begun, report any symptoms of increased thyroid
activity (hyperthyroidism) such as restlessness, rapid weight loss, and sweating.
Myxedema coma is a medical emergency that occurs when the body's level of thyroid
hormones becomes extremely low. It is treated with intravenous thyroid hormones replacement
and steroid therapy. Supportive therapy (oxygen, assisted ventilation, fluid replacement)
and intensive-care nursing may be indicated.
Support Groups:
Expectations (prognosis):
With treatment, return to the normal state is usual. Life-long medication is needed.
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,
and miscarriage.
Calling your health care provider:
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.
Prevention:
There is no prevention for hypothyroidism; however, screening tests in newborns can
detect congenital hypothyroidism.
Review Date: 5/12/2006
Reviewed By: Robert Hurd, MD, Department of Biology, College of Arts and Sciences,
Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.
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