There are a few major complications that may result from having hyperthyroidism, especially if left untreated.
Some people develop eye issues (called Graves' ophthalmopathy), which may cause gritty, red eyes or protrusion of the eyes due to swelling behind the eyeballs.2 In severe cases, double vision can develop.
Hyperthyroidism is linked to osteoporosis, which causes bone weakening, making a person more prone to breaking bones with even minor bumps or falls.
In hyperthyroidism, there is a high risk of developing atrial fibrillation, especially in older people. Atrial fibrillation is a common heart arrhythmia that can lead to serious problems like stroke or heart failure.
Thyroid storm is a rare but very serious, potentially life-threatening condition that occurs in people with untreated hyperthyroidism.3 It may also be triggered by a stressful event like surgery, trauma, or infection.
Thyroid storm is characterized by exaggerated symptoms of hyperthyroidism, such as a very fast heart rate, high fever, diarrhea, agitation, delirium, and/or decreased consciousness.
While mild hyperthyroidism in pregnancy does not usually cause problems for a mother and her baby, moderate-to-severe hyperthyroidism in a mother can lead to various complications.
For the baby, according to the American Thyroid Association, uncontrolled or untreated hyperthyroidism of the mother during pregnancy is associated with size that is small for gestational age, preterm birth, stillbirth, and possibly congenital malformations.4
For the mother, potential complications of untreated hyperthyroidism include pre-eclampsia and, rarely, thyroid storm.