People who develop a particular inflammatory disorder known as Hashimoto's thyroiditis have the most common cause of hypothyroidism.
Autoimmune disorders occur when your immune system produces antibodies that attack your own tissues. Sometimes this process involves your thyroid gland.
Scientists aren't sure why the body produces antibodies against itself. Some think a virus or bacterium might trigger the response, while others believe a genetic flaw may be involved. Most likely, autoimmune diseases result from more than one factor.
But however it happens, these antibodies affect the thyroid's ability to produce hormones.
Key word: autoimmune hypothyroidism