What Causes Hypothyroidism?

The most common cause of hypothyroidism is Hashimoto's thyroiditis. In this disease, the body's immune system mistakenly attacks its own thyroid gland. The thyroid gland cannot make enough thyroxine to keep the hormone levels in balance.

Other causes of hypothyroidism include:

• Treatments that can damage the thyroid, such as:
  • Radiation therapy to the head or neck area
  • Surgery to remove some or all of the thyroid
• Medicines, such as lithium or interferon, that may cause the thyroid to make less thyroid hormone

In rare cases, hypothyroidism may be caused by a birth defect or a problem with the pituitary gland or the hypothalamus. The pituitary gland (a small gland just below the brain) and the hypothalamus (a gland in the center of the brain) work together to control the thyroid gland.

Could you be at risk for hypothyroidism?

Men and women of any age may develop hypothyroidism. As many as 1 in 10 Americans 65 years or older may have hypothyroidism, and more than half do not know it.¹^,² However, the chances of getting the condition are higher if you:

• Are a woman older than 60 years
• Have family members with thyroid disease
• Have had thyroid surgery or radiation to the head or neck area
• Have other autoimmune disorders, such as type 1 diabetes, rheumatoid arthritis, Addison's disease, vitiligo (white patches on skin), or pernicious anemia
• Are pregnant or have just recently had a baby

The way to find out for sure if you have hypothyroidism is to see your doctor.

Next >> When to see a doctor

References
1. American Thyroid Association. ATA Hypothyroidism Booklet. Falls Church, Va: American Thyroid Association; 2003.
2. Canaris GJ, Manowitz NR, Mayor G, Ridgway EC. The Colorado thyroid disease prevalence study. Arch Intern Med. 2000;160:526-534.