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Endocrinology Health Channel

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Endocrine glands
Thyroid gland

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Hyperthyroidism

Definition

Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often referred to as an "overactive thyroid."

Alternative Names

Overactive thyroid

Causes, incidence, and risk factors

The thyroid gland is an important organ of the endocrine system. It is located in the front of the neck just below the voice box. The gland produces the hormones thyroxine (T4) and triiodothyronine (T3), which control the way every cell in the body uses energy. This process is called yourmetabolism.

Hyperthyroidism occurs when the thyroid releases too much of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including:

  • Getting too much iodine
  • Graves disease (accounts for most cases of hyperthyroidism)
  • Inflammation (thyroiditis) of the thyroid due to viral infections or other causes
  • Noncancerous growths of the thyroid gland or pituitary gland
  • Taking large amounts of thyroid hormone
  • Tumors of the testes or ovaries

Related topics:

Symptoms

  • Difficulty concentrating
  • Fatigue
  • Frequent bowel movements
  • Goiter (visibly enlarged thyroid gland) or thyroid nodules
  • Heat intolerance
  • Increased appetite
  • Increased sweating
  • Irregular menstrual periods in women
  • Nervousness
  • Restlessness
  • Weight loss (rarely, weight gain)

Other symptoms that can occur with this disease:

  • Breast development in men
  • Clammy skin
  • Diarrhea
  • Hair loss
  • Hand tremor
  • Weakness
  • High blood pressure
  • Itching - overall
  • Lack of menstrual periods in women
  • Nausea and vomiting
  • Pounding, rapid, or irregular pulse
  • Protruding eyes (exophthalmos)
  • Rapid, forceful, or irregular heartbeat (palpitations)
  • Skin blushing or flushing
  • Sleeping difficulty

Signs and tests

Physical examination may reveal thyroid enlargement, tremor, hyperactive reflexes, or an increased heart rate. Systolic blood pressure (the first number in a blood pressure reading) may be high.

Subclinical hyperthyroidism is a mild form of hyperthyroidism that is diagnosed by abnormal blood levels of thyroid hormones, often in the absence of any symptoms.

Blood tests are also done to measure levels of thyroid hormones.

  • TSH (thyroid stimulating hormone) level is usually low
  • T3 and free T4 levels are usually high

This disease may also affect the results of the following tests:

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