Complications

Left untreated, an underactive thyroid gland (hypothyroidism) caused by Hashimoto's disease can lead to a number of health problems:

• Goiter. Constant stimulation of your thyroid to release more hormones may cause the gland to become enlarged, a condition known as a goiter. Hypothyroidism is one of the most common causes of goiters. It's generally not uncomfortable, but a large goiter can affect your appearance and may interfere with swallowing or breathing.
• Heart problems. Hashimoto's disease may also be associated with an increased risk of heart disease, primarily because high levels of low-density lipoprotein (LDL) cholesterol — the "bad" cholesterol — can occur in people with an underactive thyroid gland (hypothyroidism). If left untreated, hypothyroidism can lead to an enlarged heart and, possibly, heart failure.
• Mental health issues. Depression may occur early in Hashimoto's disease and may become more severe over time. Hashimoto's disease can also cause sexual desire (libido) to decrease in both men and women and can lead to slowed mental functioning.

• Myxedema (miks-uh-DEE-muh). This rare, life-threatening condition can develop due to long-term severe hypothyroidism as a result of untreated Hashimoto's disease. Its signs and symptoms include drowsiness followed by profound lethargy and unconsciousness.

  A myxedema coma may be triggered by exposure to cold, sedatives, infection or other stress on your body. Myxedema requires immediate emergency medical treatment.

• Birth defects. Babies born to women with untreated hypothyroidism due to Hashimoto's disease may have a higher risk of birth defects than do babies born to healthy mothers. Doctors have long known that these children are more prone to intellectual and developmental problems. There may be a link between hypothyroid pregnancies and birth defects, such as a cleft palate.

  A connection also exists between hypothyroid pregnancies and heart, brain and kidney problems in infants. If you're planning to get pregnant or if you're in early pregnancy, be sure to have your thyroid level checked.