The pituitary gland at the base of the brain produces TSH, or thyroid stimulating hormone, which promotes the production of hormones by the thyroid gland. A low TSH level typically indicates an overactive thyroid gland, or hyperthyroidism. Excessive thyroid hormone increases the metabolic rate of the body, causing potentially serious complications. Effective treatment of hyperthyroidism alleviates the risks associated with excessive thyroid hormone in the body.
Eye Abnormalities and Vision Loss
Graves' disease is the most common cause of hyperthyroidism in the United States, reports the American Thyroid Association. With this disease, antibodies produced by the immune system attack the thyroid tissue, provoking overproduction of thyroid hormone. The anti-thyroid antibodies of Graves' disease may also attack the muscles and other tissues that surround the eyeballs. Swelling of the eye muscles causes eye bulging, or exophthalmos. The eyelids retract to a wide-open position and may be unable to fully close because of the exophthalmos.
In severe cases of Graves' eye disease, permanent damage to the eye muscles can lead to double vision, notes the University of Michigan Kellogg Eye Center. The overexposed eyeball may also develop ulcers and scarring, which may cloud or distort vision. In rare cases, eye tissue swelling compresses the eye nerves, potentially leading to permanent vision loss. Prompt treatment for Graves' eye disease decreases the risk for permanent eye damage.
Mental Disturbances, Seizures and Coma
Patients with profound hyperthyroidism, or thyrotoxicosis, commonly experience mental disturbances, notes "The Merck Manual for Healthcare Professionals." Possible symptoms include agitation, confusion, anxiety, nervousness, extreme mood swings and psychosis. Untreated thyrotoxicosis may provoke seizures. A surge in thyroid hormone levels, known as a thyroid storm, may lead to coma. Patients experiencing a thyroid storm require emergency medical treatment.
Heart Arrhythmias
Patients with a low TSH and elevated thyroid hormone levels typically exhibit an increased heart rate, or tachycardia. In some patients, the excess thyroid hormone triggers an abnormal heart rhythm, or an arrhythmia. "Harrison's Principles of Internal Medicine" states that atrial fibrillation is the most common arrhythmia associated with thyrotoxicosis. With atrial fibrillation, the upper heart chambers exhibit a rapid, irregular rhythm that fails to produce normal heart contractions.
Heart Failure
Hyperthyroidism stresses the heart, which beats rapidly and with increased force under the influence of excess thyroid hormone. The heart muscle may weaken under the stress of the sustained, increased workload provoked by hyperthyroidism. Heart failure can ensue, with fluid accumulation in the lungs, shortness of breath and swelling of the hands, feet and lower legs. People with underlying heart disease are at increased risk for the development of heart failure in the setting of hyperthyroidism. In a 2003 article published in the journal "Emergency Medicine," Drs. Nikolaos Stathatos and Leonard Wartofsky note that thyrotoxicosis-induced heart failure can lead to life-threatening cardiovascular shock, with markedly low blood pressure and decreased blood supply to the body organs.
References
- American Thyroid Association: Hyperthyroidism
- University of Michigan Kellogg Eye Center: Graves' Eye Disease
- Merck Manual for Healthcare Professionals: Hyperthyroidism (Thyrotoxicosis)
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al., Editors; 2004
- "Emergency Medicine"; Thyroid Emergency: Are You Prepared?; Nikolaos Stathatos, M.D., Leonard Wartofsky, M.D.; February 2003
