Causes of hypothyroidism

Autoimmune thyroiditis - The body's immune system may produce a reaction in the thyroid gland that results in hypothyroidism and, most often, a goiter (enlargement of the thyroid). The most common cause of thyroid gland failure is called autoimmune thyroiditis or Hashimoto's thyroiditis, which is created by the immune system itself.

Congenital condition - An infant may be born with an inadequate amount of thyroid tissue or an enzyme defect that does not allow normal thyroid hormone production.

Medical treatments - The second major cause is the broad category of "medical treatments."  The treatment of many thyroid conditions requires surgical removal of a part or all of the thyroid gland (thyroid cancer). Hypothyroidism occurs when thyroid producing cells remaining after surgery are not enough to meet the needs of the body.

Medications - Lithium, high doses of iodine, and amiodarone (Cordarone, Pacerone) can cause hypothyroidism.

Radioactive iodine treatment - Hypothyroidism can develop as a desired therapeutic goal after the use of radioactive iodine treatment for hyperthyroidism.

Thyroid Operation - Hypothyroidism may be related to surgery on the thyroid gland, especially if most of the thyroid has been removed.

Pituitary hypothyroidism - Any destructive disease of the pituitary gland may cause damage to the cells that secrete Thyroid Stimulating Hormone (TSH), which stimulates the thyroid to produce normal amounts of thyroid hormone. This is a very rare cause of hypothyroidism.

Postpartum thyroiditis - Shortly after pregnancy, the thyroid may go through a period of hyperthyroidism, followed by hypothyroidism, and then most often returns to normal function.

Subacute thyroiditis - Painful inflammation of the thyroid, the cause of which is unknown, may cause hypothyroidism after a period of overactivity (hyperthyroidism).

Spontaneous onset - Underproduction of thyroid hormones (hypothyroidism) can occur for no apparent reason.

Risk factors
Risk factors increase the likelihood of experiencing a disease or condition. A number of different factors can combine and make it more likely that a person will experience hypothyroidism. For example, people with certain medical conditions have a higher risk for hypothyroidism. Examples of medical conditions that increase risk of thyroid problems include:

• Addison's disease
• Anorexia or bulimia
• Autoimmune diseases
• Gout
• Myasthenia gravis
• Polycystic ovarian syndrome
• Turner syndrome

Other risk factors for hypothyroidism include:

Age - The risk for hypothyroidism is greatest after 50 and increases with age.

Ethnicity - African-Americans may be less likely to have thyroid disease than Caucasians and Asians.

Gender - Women have 10 times the risk of hypothyroidism as men, with a significant increase in risk after age 34. Changes during both pregnancy and menopause should be carefully monitored.

Genetics - Genetics plays a role in many cases of underactive and overactive thyroid. The genetics involved with hypothyroidism are complicated, however. Certain genetic features, for example, appear to play a role in Hashimoto's thyroiditis and postpartum thyroiditis in Caucasians, but others affect different ethnic groups.

Medications - People of any age can get hypothyroidism, although people taking drugs are more at risk for developing problems that affect the thyroid. Therefore anyone being treated for a chronic disease, taking thyroid medication, and those at risk for a thyroid disorder should be aware of the impact these drugs may have on the thyroid.

Smoking - Smoking significantly increases risk for thyroid disease, particularly autoimmune Hashimoto's thyroiditis and postpartum thyroiditis. Chemicals in cigarette smoke called thiocyanates appear to have especially harmful effects on the thyroid.

Early identification and diagnosis of thyroid problems is key to receiving the best treatment available.  Do you know how to identify the symptoms of Hypothyroidism? While some of the symptoms of Hypothyroidism are well known, there are additional symptoms to look for. Read the following symptoms section for more information about symptoms of hypothyroidism.