Hyperthyroidism
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More InDepth Information on This Condition

Definition
The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hyperthyroidism occurs when the thyroid gland becomes overactive and produces too much thyroid hormone.

The Thyroid Gland

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Causes
Hyperthyroidism may be caused by:

  • Graves' disease —an autoimmune disorder that occurs when the immune system produces antibodies that attack cells of the thyroid gland
  • Thyroid nodules:
    • Toxic uninodular goiter—a single area/nodule in the thyroid gland is overactive
    • Toxic multinodular goiter—multiple nodules in the thyroid gland which overproduce thyroid hormone
  • Thyroiditis—inflammation of the thyroid that may later lead to hypothyroidism
  • Taking too much thyroid hormone—very rarely from meat sources contaminated by animal thyroid glands
Risk Factors
Factors that may increase your chance of having hyperthyroidism include:

  • Pregnancy—postpartum thyroiditis (hyperthyroidism followed by hypothyroidism)
  • Family history of Graves' disease
  • Certain viral infections
  • Smoking
Symptoms
Symptoms come on slowly. As the thyroid becomes more overactive, symptoms may appear.

Hyperthyroidism may cause:

  • Heart palpitations—more common in people over 50 years old
  • Rapid or irregular pulse
  • Shortness of breath
  • Fatigue
  • Heat intolerance
  • Itchiness
  • Nervousness, restlessness, or irritibility
  • Insomnia
  • Goiter —enlarged thyroid gland
  • Increased number of bowel movements/diarrhea
  • Irregular or no menstrual periods
  • Unexplained weight loss despite an increased appetite
  • Increased sweating
  • Tremors
  • Double vision
  • Lumpy, red thickening of the skin in front of the shins
Diagnosis
The doctor will ask about your symptoms and medical history. A physical exam will be done.

Tests may include:

  • Blood tests —to measure level of thyroid hormones and look for thyroid antibodies
  • Radioactive iodine uptake test—to measure how much iodine the thyroid gland absorbs over the course of several hours
Treatment
Treatment will depend what is causing the hyperthyroidism. It will also be adjusted if you are pregnant. Talk to your doctor about the best treatment options for you.

Options include:

Antithyroid Drugs
Antithyroid medications work best for Graves' disease. They will reduce thyroid activity. Smoking can interfere with some of the medications. If you smoke, talk to your doctor about how you can successfully quit .

All theses medications can cause a rash, fever and painful joints. Serious adverse reactions include increased risk of infection and liver damage.

If the disease goes into remission, you may no longer need medication.

Beta-Blockers
This type of medication can relieve rapid heart rate and nervousness.

Radioactive Iodine
Radioactive iodine is taken orally. It is then absorbed by the thyroid gland. Once there, it damages most of the thyroid cells. These cells can no longer produce thyroid hormones. Within days, the excess iodine passes out of the body in the urine or changes into a nonradioactive state. This treatment reduces the activity of the thyroid. Sometimes the treatment can decrease the thyroid levels too much. In this case, you will need to take a daily thyroid hormone replacement.

Surgery
Surgery is uncommon for the treatment of hyperthyroidism. It will remove part or all of the thyroid. It may be an option when medical therapy fails.

After a thyroidectomy, you may need to take daily thyroid, calcium, or vitamin D supplements.

Eye Protection
If there are eye symptoms like dry red eyes or double vision, your doctor may prescribe:

  • Eye protection before sleep
  • Artificial tears
  • Sunglasses
You may be referred to an eye specialist.

Prevention
There are no current guidelines to prevent hyperthyroidism.




RESOURCES:
The American Thyroid Association

National Graves' Disease Foundation

CANADIAN RESOURCES

Thyroid Foundation of Canada

References:
American Association of Clinical Endocrinologists. Medical guidelines for clinical practice for the evaluation and treatment of hyperthyroidism and hypothyroidism. Endocrine Practice. 2002;8:457-469.

Hyperthyroidism. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated March 12, 2013. Accessed November 25, 2013.

Shomon M. Frequently asked questions on Graves' disease & hyperthyroidism. Thyroid-Info website. Available at: http://www.thyroid-info.com/articles/hyperthyroidism-faq.htm. Updated November 25, 2013. Accessed November 25, 2013.

Van Geest RJ, Sa sim IV, Koppeschaar HP, et al. Methylprednisolone pulse therapy for patients with moderately severe Graves' orbitopathy: a prospective, randomized, placebo-controlled study. Eur J Endocrinol. 2008;148:229-237.

1/30/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Nyirenda MJ, Taylor PN, Stoddart M, Beckett GJ, Toft AD. Thyroid-stimulating hormone-receptor antibody and thyroid hormone concentrations in smokers vs nonsmokers with Graves disease treated with carbimazole. JAMA. 2009;301:162-164.

7/6/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Safety: propylthiouracil. US Food and Drug Administration website. Available at: http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm164162.htm. Updated April 21, 2010. Accessed November 25, 2013.

6/10/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Alhefdhi A, Mazeh H, et al. Role of postoperative vitamin D and/or calcium routine supplementation in preventing hypocalcemia after thyroidectomy: a systematic review and meta-analysis. Oncologist. 2013;18(5):553-542.

Last Reviewed November 2013



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