Hyperthyroidism

Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone (thyroxine and triiodothyronine). Excess hormone accelerates metabolism, which can cause weight loss, rapid or irregular heartbeat, sweating, nervousness, and other symptoms.

The most common cause is Graves’ disease, an autoimmune disorder. Other causes include toxic nodular goiter, thyroiditis, and excess iodine or thyroid hormone intake. Hyperthyroidism is treatable with medicines, radioactive iodine, or surgery. Untreated, it can lead to heart problems, brittle bones, and a rare life-threatening crisis called thyroid storm.

Symptoms can include:

• Unintentional weight loss despite normal or increased appetite
• Tachycardia, palpitations, or irregular heartbeat (including atrial fibrillation)
• Nervousness, anxiety, or irritability
• Tremor (usually of the hands and fingers)
• Increased sweating and heat intolerance
• Changes in menstrual patterns
• More frequent bowel movements
• Enlarged thyroid gland (goiter)
• Fatigue and muscle weakness
• Difficulty sleeping
• Thinning skin and fine, brittle hair
• In Graves’ disease: bulging eyes (Graves’ orbitopathy), redness or swelling around the eyes, and rare skin changes on the shins (pretibial myxedema)

Older adults may present mainly with fatigue, weight loss, or atrial fibrillation rather than classic hyperactive symptoms.

Common causes include:

• Graves’ disease — autoantibodies stimulate the thyroid-stimulating hormone (TSH) receptor
• Toxic multinodular goiter and toxic adenoma — autonomous hormone-producing nodules
• Thyroiditis — temporary leakage of stored hormone (subacute, postpartum, silent); often followed by a hypothyroid phase
• Excess iodine intake or iodine-containing medicines (e.g., amiodarone)
• Over-replacement with thyroid hormone tablets
• Rare: pituitary TSH-secreting tumors or gestational trophoblastic disease

Risk factors include:

• Female sex
• Family history of Graves’ disease or other autoimmune thyroid disease
• Personal history of other autoimmune diseases (type 1 diabetes, rheumatoid arthritis, celiac disease, vitiligo)
• Recent pregnancy (postpartum thyroiditis or new Graves’)
• Smoking (especially increases risk of Graves’ eye disease)
• Excess iodine exposure

Possible complications include:

• Atrial fibrillation and heart failure
• Osteoporosis and fracture risk
• Graves’ orbitopathy with risk to vision in severe cases
• Red, swollen skin on the shins or feet (Graves’ dermopathy)
• Thyrotoxic periodic paralysis (rare, more often in Asian males)
• Thyroid storm (rare medical emergency)
• Pregnancy complications if uncontrolled (miscarriage, preterm birth, maternal heart failure, fetal thyroid dysfunction)

Most causes of hyperthyroidism cannot be prevented. Not smoking reduces the risk and severity of Graves’ eye disease. People on thyroid hormone should take the correct dose and have periodic monitoring so over-replacement is avoided.

Evaluation typically includes:

• TSH — suppressed in primary hyperthyroidism
• Free T4 and total or free T3 — elevated
• TSH-receptor antibodies (TRAb/TSI) to support Graves’ disease
• Radioactive iodine uptake and scan — high diffuse uptake in Graves’; focal uptake in toxic nodules; low uptake in thyroiditis or exogenous hormone
• Thyroid ultrasound — especially when nodules are present or uptake scanning is not available
• Eye evaluation when orbitopathy is suspected

See a healthcare professional for unexplained weight loss, persistent rapid heartbeat, anxiety, tremor, or heat intolerance. Seek emergency care for symptoms of thyroid storm: high fever, severe agitation or confusion, marked tachycardia, or vomiting and diarrhea in someone with known or suspected hyperthyroidism.

Treatment depends on cause, severity, age, pregnancy status, and patient preference:

• Antithyroid drugs — methimazole (preferred in most non-pregnant patients) or propylthiouracil (preferred in first trimester of pregnancy); monitor for rare agranulocytosis and liver injury
• Radioactive iodine ablation — definitive therapy for many with Graves’ or toxic nodules; leads to hypothyroidism requiring lifelong levothyroxine in most cases
• Surgery (thyroidectomy) — for large goiters, suspected cancer, moderate-to-severe orbitopathy, or patient preference; requires lifelong hormone replacement if total thyroidectomy is performed
• Beta-blockers — control heart rate, tremor, and anxiety until hormone levels are controlled
• Supportive care for thyroiditis — beta-blockers and time; antithyroid drugs are not useful when the problem is hormone leakage rather than overproduction
• Graves’ orbitopathy — supportive care, selenium in mild cases, steroids, teprotumumab, orbital radiation, or surgery for moderate-to-severe disease

Helpful measures:

• Take medicines exactly as prescribed and keep laboratory appointments
• Do not smoke
• Eat adequate calories if weight loss is significant until hormone levels normalize
• Protect eyes (lubricating drops, sunglasses, elevating the head of the bed) if mild orbitopathy is present
• Report fever, sore throat, or severe fatigue while on antithyroid drugs (possible low white-cell count)
• Inform all clinicians of planned pregnancy or new pregnancy immediately

Bring:

• List of symptoms and when they began
• Personal and family history of thyroid or autoimmune disease
• Complete medication and supplement list (including biotin, which can interfere with thyroid tests)
• Previous thyroid test results
• Questions about treatment options (medicines vs radioactive iodine vs surgery), eye disease, and pregnancy