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Alternative Names Return to topMyxedema; Adult hypothyroidism
Definition Return to top
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.
Causes Return to top
The thyroid gland is located in the front of the neck just below the voice box (larynx). It releases hormones that control metabolism.
The most common cause of hypothyroidism is inflammation of the thyroid gland, which damages the gland's cells. Autoimmune or Hashimoto's thyroiditis, in which the immune system attacks the thyroid gland, is the most common example of this. Some women develop hypothyroidism after pregancy (often referred to as "postpartum throiditis").
Other common causes of hypothyroidism include:
Certain drugs can cause hyperthyroidism, including:
Risk factors include:
Symptoms Return to top
Late symptoms, if left untreated:
Exams and Tests Return to top
A physical examination may reveal a smaller-than-normal thyroid gland, although sometimes the gland is normal size or even enlarged (goiter). The examination may also reveal:
A chest x-ray may show an enlarged heart.
Laboratory tests to determine thyroid function include:
Lab tests may also reveal:
Treatment Return to top
The purpose of treatment is to replace the thyroid hormone that is lacking. Levothyroxine is the most commonly used medication. Doctors will prescribe the lowest dose that effectively relieves symptoms and brings the TSH level to a normal range. If you have heart disease or you are older, your doctor may start with a very small dose.
Lifelong therapy is required unless you have a condition called transient viral thyroiditis.
You must continue taking your medication even when your symptoms go away. When starting your medication, your doctor may check your hormone levels every 2 - 3 months. After that, your thyroid hormone levels should be monitored at least every year.
Important things to remember when you are taking thyroid hormone are:
After you start taking replacement therapy, tell your doctor if you have any symptoms of increased thyroid activity (hyperthyroidism) such as:
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 hormone replacement and steroid medications. Some patients may need supportive therapy (oxygen, breathing assistance, fluid replacement) and intensive-care nursing.
Outlook (Prognosis) Return to top
In most cases, thyroid levels return to with proper treatment. However, thyroid hormone replacement must be taken for the rest of your life.
Myxedema coma can result in death.
Possible Complications Return to top
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 people with untreated hypothyroidism.
Symptoms and signs of myxedema coma include:
Other complications are:
People with untreated hypothyroidism are at increased risk for:
People treated with too much thyroid hormone are at risk for angina or heart attack, as well as osteoporosis (thinning of the bones).
When to Contact a Medical Professional Return to top
Call your health care provider if you have symptoms of hypothyroidism (or myxedema).
If you are being treated for hypothyroidism, call your doctor if:
Prevention Return to top
There is no prevention for hypothyroidism.
Screening tests in newborns can detect hypothyroidism that is present from birth (congenital hypothyroidism).
References Return to top
Fatourechi V. Subclinical hypothyroidism: an update for primary care physicians. Mayo Clin Proc. 2009;84(1):65-71.
Ladenson P, Kim M. Thyroid. In: Goldman L and Ausiello D, eds. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007:chap 244.
Vaidya B, Pearce SH. Management opf hypothyroidism in adults. BMJ. 2008;28;337:a801.Update Date: 4/29/2009 Updated by: Deborah Wexler, MD, Assistant Professor of Medicine, Harvard Medical School, Endocrinologist, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.