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    Hypothyroidism

    Myxedema; Adult hypothyroidism

    Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. This condition is often called underactive thyroid.

    Causes

    The thyroid gland is an important organ of the endocrine system. It is locatedatthe front of the neck, just above where your collarbones meet. The thyroid makes hormones that control the way every cell in the body uses energy. This process is called metabolism.

    Hypothyroidism is more common in women and people over age 50.

    The most common cause of hypothyroidism is thyroiditis. Swelling and inflammationdamage the thyroid gland's cells.

    Causes of this problem include:

    • The immune systemattackingthe thyroid gland
    • Viral infections (common cold) or other respiratory infections
    • Pregnancy (often called postpartum thyroiditis)

    Other causes of hypothyroidism include:

    • Certain medicines, such as lithium and amiodarone
    • Congenital (birth) defects
    • Radiation treatments to the neck or brain to treat different cancers
    • Radioactive iodine used to treat an overactive thyroid gland
    • Surgical removal of part or all of the thyroid gland
    • Sheehan syndrome, a condition that may occur in a woman who bleeds severely during pregnancy or childbirth and causes the destruction of the pituitary gland
    • Pituitary tumor or pituitary surgery

    Symptoms

    Early symptoms:

    • Hard stools or constipation
    • Increased sensitivity to cold temperature
    • Fatigue or feeling slowed down
    • Heavier and irregular menstrual periods
    • Joint or muscle pain
    • Paleness or dry skin
    • Sadness or depression
    • Thin, brittle hair or fingernails
    • Weakness
    • Weight gain

    Late symptoms, if untreated:

    • Decreased taste and smell
    • Hoarseness
    • Puffy face, hands, and feet
    • Slow speech
    • Thickening of the skin
    • Thinning of eyebrows

    Exams and Tests

    The health care provider will do a physical exam and find that your thyroid gland is enlarged.Sometimes, the gland is normal size or smaller-than-normal. The exam may also reveal:

    • Brittle nails
    • Coarse features of the face
    • Pale or dry skin, which may be cool to the touch
    • Swelling of the arms and legs
    • Thin and brittle hair

    Blood tests are also ordered to measure your thyroid hormones TSH and T4.

    You may also have tests to check:

    • Cholesterol levels
    • Complete blood count (CBC)
    • Liver enzymes
    • Prolactin
    • Sodium

    Treatment

    Treatment is aimed at replacing the thyroid hormone thatyou arelacking.

    Levothyroxine is the most commonly used medicine:

    • You will be prescribed the lowest dose possible that relieves your symptoms and brings your blood hormone levels back to normal.
    • If you have heart disease or you are older, your doctor may startyou ona very small dose.
    • Most people with an underactive thyroid will need to take this medicine for life.

    When starting your medicine, your doctor may check your hormone levels every 2to 3 months. After that, your thyroid hormone levels should be monitored at leastonceeveryyear.

    When you are taking thyroid medicine, be aware of the following:

    • Donot stop taking the medicine when you feel better. Continue takingit exactly as your doctor prescribed.
    • If you change brands of thyroid medicine, let your doctor know. Your levels may need to be checked.
    • What you eat can change the way your body absorbs thyroid medicine. Talk with your doctor if you are eating a lot of soy products or are on a high-fiber diet.
    • Thyroid medicine works best on an empty stomach and when taken 1 hour before any other medications. Ask your doctor is you should take your medicine at bedtime. Studies have found that taking it at bedtime may allow your body to absorb the medicine better than taking it in the daytime.
    • Wait at least 4 hours after taking thyroid hormone before youtake fiber supplements, calcium, iron, multivitamins, aluminum hydroxide antacids, colestipol, or medicines that bind bile acids.

    While you are taking thyroid replacement therapy, tell your doctor if you have any symptomsthat suggest your dose is too high,such as:

    • Palpitations
    • Rapid weight loss
    • Restlessness or shakiness
    • Sweating

    Outlook (Prognosis)

    In most cases, thyroid hormone levels return to normal with proper treatment. You will likelytake athyroid hormonemedicine for the rest of your life.

    Myxedema coma, the most severe form of hypothyroidism, is rare. It occurs when thyroid hormone levels get very low. Itcan be caused by an infection, illness, exposure to cold, or certain medicines in people with untreated hypothyroidism.

    Myxedema coma is a medical emergency that must be treated in the hospital. Some patients may need oxygen, breathing assistance (ventilator), fluid replacement and intensive-care nursing.

    Symptoms and signs of myxedema coma include:

    • Below normal temperature
    • Decreased breathing
    • Low blood pressure
    • Low blood sugar
    • Unresponsiveness
    • Inappropriate or uncharacteristic moods

    People with untreated hypothyroidism are at increased risk of:

    • InfectionInfertility, miscarriage, giving birth to a baby with birth defects
    • Heart disease because of higher levels of LDL ("bad") cholesterol
    • Heart failure

    When to Contact a Medical Professional

    Call your health care provider if you have symptoms of hypothyroidism (or myxedema).

    If you are being treated for hypothyroidism, call your doctor if:

    • You develop chest pain or rapid heartbeat
    • You have an infection
    • Your symptoms get worse or do not improve with treatment
    • You develop new symptoms

    References

    Brent GA, Davies TF. Hypothyroidism and thyroiditis. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, et al. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa.: Elsevier Saunders; 2011:chap 13.

    Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid. 22;12:1200-1235.

    Kim M, Ladenson P. Thyroid. In: Goldman L, Schafer AI, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia, Pa.: Elsevier Saunders; 2011:chap 233.

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      A Closer Look

      Tests for Hypothyroidism

        Review Date: 6/7/2013

        Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.

        The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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