Thyroid Eye Disease
Graves’ eye disease, also known as thyroid eye disease, is an autoimmune condition in which immune cells attack the thyroid gland, which in turn responds by secreting an excess amount of thyroid hormone. As a result, the inflamed thyroid gland can enlarge (“goiter”) and excess hormone changes metabolism and affects the function of the heart, brain and other organs. The hyperthyroid state is characterized by fast pulse/heartbeat, palpitations, increased sweating, high blood pressure, irritability, fatigue, weight loss, heat intolerance, and loss of hair and alterations in hair quality. At times, people in the hyperthyroid state can be diagnosed with a psychiatric disorder, such as bipolar or manic disorder, while in fact they have a side effect of hyperthyroidism.
The eyes are particularly vulnerable to thyroid disease, because the immune system that attacks the thyroid gland often also targets the eye muscles and connective tissue within the eye socket. The skin is also affected, but to a lesser degree in most patients. The immunologic attack on the tissues of the orbit results in scarring of the orbital tissues, enlargement of the eye muscles, and expansion of the fat compartment that is present to protect the eye. The exact trigger for thyroid eye disease is not known, but the orbital tissues likely share some antigenic features with the thyroid gland. In addition, the orbital tissues contain receptors and enzymes that respond to changes in thyroid hormone levels. Eye symptoms can range from mild to severe, but only 10-20% of patients have vision-threatening disease.
Thyroid eye disease can also be present when the level of thyroid hormone in the blood is normal (euthyroid) or low (hypothyroid), depending on the degree of glandular stimulation caused by the immune attack and by the amount of thyroid gland destruction present at the time of diagnosis. However, most patients with eye symptoms have abnormal hormone levels that are accompanied by specific antibodies in the blood stream (for example, TSI – thyroid stimulating immunoglobulin). The components of the disease affecting the thyroid gland versus the eyes have common causes, but evolve separately and each must be treated separately.