A goiter (GOI-tur) is an abnormal enlargement of your thyroid gland; a butterfly-shaped gland located at the base of your neck. Though usually painless, a large goiter can cause coughing and difficulty when swallowing or breathing.The most common cause of goiters worldwide are diets lacking in iodine.

Though not all goiters cause signs and symptoms. Their occurrence may include:
Vvisible swelling at the base of your neck
A tight feeling in your throat
Difficulty swallowing
Difficulty breathing

Iodine deficiency.
The lackof the element Iodine in one’s diet. It is an essential mineral found in fish, seaweed, shellfish, dairy products and eggs.
Graves' disease.
Antibodies produced by your immune system mistakenly attack your thyroid gland, causing it to swell.
Hashimoto's disease.
An autoimmune disorder where the damage to the thyroid gland makes hormone production low, causing it to swell.
Thyroid cancer.

Risk factors
A lack of dietary iodine
People living in areas where iodine is in short supply and who don't have access to iodine supplements are at high risk of goiters.
Women at greater risk
Women are biologically prone to thyroid disorders
Medical history
Having a family history autoimmune disease increases your risk.
Pregnancy and menopause
Certain medications
Medications such as the heart drug Amiodarone and the Psychiatric drug Lithium increase risk.
Radiation exposure
Radiation treatments in the neck and chest area, or being exposed ro radioactivity increase risk.

SOURCES: http://www.mayoclinic.org/diseases-conditions/goiter/home/ovc-20264589;
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