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    Overactive Thyroid (Hyperthyroidism)

    Causes of Hyperthyroidism continued...

    Excess iodine. You may also develop hyperthyroidism if you eat, drink, or are otherwise exposed to substances that contain a high amount of iodine. Iodine is used by the body to make thyroid hormone. Kelp or seaweed supplements and the medication amiodarone (Cordarone, Pacerone), once used to treat irregular heartbeats, are examples of medicines that contain a lot of iodine.

    Thyroid medications. Taking too much thyroid hormone medication can wreak havoc on your thyroid gland and cause hyperthyroidism. If you have been prescribed thyroid replacement hormone (for hypothyroidism), never take an extra dose, even if you missed one, without first talking to your doctor.

    Symptoms of Hyperthyroidism

    Symptoms of hyperthyroidism may be vague and can often mimic other illnesses and conditions. If you have a very mild form of hyperthyroidism, you may not notice any symptoms. Symptoms are often particularly subtle in the elderly. However, an overactive thyroid often leads to discomfort or even disability that disrupts your everyday activities or routines.

    Thyroid enlargement, called a goiter, occurs in most people with hyperthyroidism. You may see or feel a lump in the front of your neck. Sometimes only your doctor will be able to detect a goiter.

    Other symptoms of hyperthyroidism include:

    • Anxiety, nervousness, and irritability
    • Frequent, loose bowel movements
    • Difficulty sleeping
    • Double vision
    • Eyes that bulge out, or "protrude" (in patients with Graves' disease)
    • Hair changes, including brittle hair, thinning hair, and hair loss from scalp
    • Irregular heart beat (arrhythmia), especially in older adults
    • Menstrual cycle changes, including lighter bleeding and less frequent periods
    • Muscle weakness, especially in the thighs and upper arms
    • Rapid fingernail growth
    • Rapid heartbeat, usually over 100 beats per minute
    • Shaky hands
    • Sweating
    • Thinning skin
    • Weight loss despite increased appetite

    Make an appointment with your health care provider if you have any of these symptoms. It is important to note that these symptoms can be due to other medical conditions and disorders ranging from anxiety to a tumor of the adrenal gland.

    How Is Hyperthyroidism Diagnosed?

    Blood tests can confirm a diagnosis of hyperthyroidism. Blood tests include those for thyroid-stimulating hormone (TSH). This is a hormone released by the pituitary gland to stimulate the thyroid to make thyroid hormone. Other blood tests include measures of thyroid hormone levels (typically elevated) and thyroid-stimulating antibody (called thyroid-stimulating immunoglobin test) to check for Graves' disease. If your test results are abnormal, your doctor may also order the following tests:

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