Hyperthyroidism: When Your Thyroid Becomes Too Active

Singer Missy Elliott had it. So did former first lady Barbara Bush and former president George H.W. Bush (and their dog Millie!). An overactive thyroid gland—hyperthyroidism—is not as common as an underactive one, but its manifestations can be more acute and dramatic.

The most common cause is Graves’ disease which, like Hashimoto’s thyroiditis, is the result of the body’s immune system attacking its own thyroid gland. Unlike Hashimoto’s disease, in which the autoantibodies typically destroy the gland, in Graves’ disease, the antibodies stimulate the thyrotropin (TSH) receptors in the thyroid, leading instead to increased production and release of thyroid hormone.

Hashimoto’s and Graves’ may actually represent the two ends of a single spectrum of autoimmune disease, since they often occur with high frequency together in many families and can overlap in some of their clinical manifestations.

Other causes of hyperthyroidism include viral infections of the thyroid gland, which can cause the rapid release of thyroid hormone from the gland, usually followed by a period of hypothyroidism as the gland recovers, and a hyperactive thyroid nodule. Thyroid cancers are almost never hyperactive and do not cause hyperthyroidism.

Hyperthyroidism magnifies all the processes that thyroid hormone normally regulates. Patients can therefore experience a rapid heartbeat, profuse sweating, heat intolerance, insomnia, diarrhea, and weight loss. They look like their bodies have gone into overdrive. All this heightened metabolic activity can lead to profound weight loss, fatigue, and weakness.

Patients with Graves’ Disease can also develop marked bulging of the eyes, to the point that their eyelids do not fully close and they may look like they are constantly staring ahead. This condition is caused by the autoimmune process affecting the muscles around the eye.

Other symptoms may include a tremor, most evident when patients extend their hands outward, abnormal heart rhythms, and hypertension. Elderly patients, however, may demonstrate virtually none of these symptoms and instead experience depression, weight loss, constipation, and loss of appetite. Often, the only finding in older patients is atrial fibrillation, an abnormal heart rhythm, which may only be detected in a physical exam or on an EKG.

Lastly, we should mention one potentially devastating manifestation of hyperthyroidism. A condition called thyroid storm can occur in patients with untreated hyperthyroidism who undergo a significant stress, such as surgery or a severe illness. These patients can suddenly develop a very high fever, rapid and abnormal heart rhythms, congestive heart failure (they may even experience a heart attack), and delirium. Urgent treatment is critical for this condition, which can be fatal.

The diagnosis of hyperthyroidism is confirmed by blood tests revealing increased thyroid hormones (T3 and/or T4) and a suppressed level of the pituitary hormone TSH, which regulates the thyroid gland.

Treatment of Graves’ disease or an overactive thyroid nodule involves one of three basic modalities:

• Medications that inhibit the synthesis of thyroid hormones.
• Radioactive iodine, which destroys thyroid tissue and is the most common treatment for Graves’ disease. It can’t be used in pregnant women since it can cross the placenta and damage the fetus’s thyroid gland.
• Surgery—used mostly for overactive thyroid nodules.