An overactive thyroid produces too much hormone, speeding up the body's metabolism and causing a distinct set of symptoms. Dr. Guttler explains the causes, diagnosis, and treatment options.
Hyperthyroidism occurs when the thyroid gland produces excess thyroid hormone, causing the body's metabolism to accelerate. It affects approximately 1% of the US population and is more common in women. Left untreated, hyperthyroidism can lead to serious complications including heart arrhythmias, osteoporosis, and thyroid storm — a rare but life-threatening emergency.
The most common cause is Graves' disease, an autoimmune condition in which antibodies stimulate the thyroid to overproduce hormone. Other causes include toxic multinodular goiter (multiple overactive nodules), a single toxic adenoma (one overactive nodule), thyroiditis (inflammation causing temporary hormone release), and excessive iodine intake. Rarely, hyperthyroidism is caused by a TSH-secreting pituitary tumor.
Symptoms reflect the body's accelerated state: rapid or irregular heartbeat (palpitations), unintentional weight loss despite increased appetite, nervousness, anxiety, and irritability, tremor in the hands and fingers, increased sweating and heat intolerance, frequent bowel movements, fatigue and muscle weakness, difficulty sleeping, and in women, lighter or less frequent menstrual periods. Older patients may present with only heart-related symptoms — a presentation called 'apathetic hyperthyroidism.'
Diagnosis is confirmed with blood tests showing a suppressed TSH and elevated Free T4 and/or Free T3. Thyroid antibody tests (TSI, TRAb) help identify Graves' disease. A radioactive iodine uptake scan distinguishes Graves' disease from thyroiditis and toxic nodules. Thyroid ultrasound assesses gland size and identifies nodules. An electrocardiogram may be needed if cardiac symptoms are present.
Three main treatments exist: antithyroid medications (methimazole or propylthiouracil) block hormone production and are often the first-line approach; radioactive iodine (RAI) therapy destroys overactive thyroid tissue and is highly effective; and thyroid surgery (thyroidectomy) removes part or all of the gland. The choice depends on the cause, severity, patient age, pregnancy status, and personal preference. Beta-blockers provide rapid symptom relief while definitive treatment takes effect.
Graves' disease is uniquely associated with thyroid eye disease (Graves' ophthalmopathy), in which the immune system attacks the tissues around the eyes. Symptoms range from mild eye irritation and puffiness to severe proptosis (bulging eyes), double vision, and vision loss. Thyroid eye disease requires specialized management and may need treatment independent of thyroid function.
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