Nearly 5% of Americans over the age of 12 have hypothyroidism.
It is most common in women.
Hashimoto’s disease is a common cause of hypothyroidism. When someone has Hashimoto’s disease, their immune system attacks the thyroid, which then can’t produce enough hormones.
People with celiac disease, Sjögren’s syndrome, diabetes, rheumatoid arthritis, or lupus may be more likely to have an underactive thyroid.
If an underactive thyroid is not treated during pregnancy, women can experience high blood pressure in late pregnancy, anemia, miscarriage, low birth weight, or stillbirth.
Infants can also have an underactive thyroid. All newborns in the U.S. are tested for congenital hypothyroidism.