What Causes Hypothyroidism?

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About Hypothyroidism

The primary role of the thyroid is to produce hormones that regulate the body’s metabolism. People with hypothyroidism do not produce functional thyroid hormones, or in some cases don’t produce the hormones at all. In the U.S. more than five million people are affected by hypothyroidism, and it has been estimated that around ten percent of women have thyroid deficiency.

People with hypothyroidism tend to have symptoms of very slow metabolism, but the actual symptoms of the disease often vary between individuals. This is because all cells that are metabolically active use thyroid hormone. Symptoms of hypothyroidism may include the following:

  • Fatigue and low energy levels, sleepiness
  • Unexplained weight gain and/or decreased appetite
  • Intolerance to cold
  • Dry skin, hair loss
  • Joint and muscle pain
  • Depression and/or emotional instability
  • Impaired memory and ability to concentrate
  • Blurred vision
  • Disturbances in menstrual cycle
  • Feeling of fullness in the throat, often accompanied by hoarseness

Causes of Hypothyroidism

There are several different causes of hypothyroidism, ranging from mineral deficiency to cancer.

  • Iodine deficiency is the number one cause of hypothyroidism across the world. In the Western world, however, iodine intake tends to be of an adequate level, and thyroid deficiency caused by autoimmune disease is the most common.

  • Thyroid autoimmune disease is called Hashimoto thyroiditis. This disease develops when the immune system begins to attack the thyroid gland, causing a chronic immune response that reduces thyroid function.

  • Up to ten percent of women develop lymphocytic thyroiditis after giving birth. For many women this condition is temporary, but some women may develop permanent hypothyroidism.

  • Subacute granulomatous thyroiditis causes inflammation of the thyroid, leading to hypothyroidism which may be permanent in some people.

  • People with Graves disease are treated with radioactive iodine, which almost always permanently destroys thyroid function, leading to hypothyroidism.

  • External neck irradiation (required by people with Hodgkin disease and some other types of cancer) may cause hypothyroidism

Hypothyroidism Treatment

The standard treatment for hypothyroidism involves replacing the hormone that the body can no longer produce on its own. Daily intake of synthetic thyroid hormones, in the form of levothyroxine, restores the body’s levels and restores normal metabolism. For most people with hypothyroidism, levothyroxine treatment is a permanent requirement, but reassessment is needed periodically to ensure the dose is adequate.

Resources

Hypothyroidism Information at eMedicine

Hypothyroidism: Too Little Thyroid Hormone. By James Norman MD, FACS, FACE.

The Mayo Clinic on Hypothyroidism