Hyperthyroidism: Causes, Symptoms, Diagnosis, and Treatment
Also known as: Overactive thyroid, Thyrotoxicosis
What is hyperthyroidism?
Hyperthyroidism is the excessive production of thyroid hormones by the thyroid gland, which speeds up the body’s metabolism. The NIDDK puts the overall figure at about 1 out of 100 Americans ages 12 years and older, and notes the condition is more common in women and in people older than 60. The gap between the sexes is wide: the Whickham Survey, which studied thyroid disorders in northeast England, found hyperthyroidism in 2.7% of women compared with 0.23% of men, roughly a tenfold difference. The most common cause is Graves’ disease, an autoimmune condition, followed by toxic thyroid nodules and certain types of thyroiditis.
Causes and risk factors
Graves’ disease causes about 4 out of 5 cases of hyperthyroidism in the United States, according to the NIDDK. It is driven by antibodies that abnormally stimulate the thyroid, and it affects nearly 1 in 100 Americans overall. Other causes include:
- Toxic multinodular goiter and toxic adenoma (a single overactive nodule)
- Thyroiditis, a temporary inflammation of the thyroid, which can be subacute, postpartum, or painless
- Too much iodine, from diet or supplements
- Too much thyroid hormone medicine, usually when a dose is set too high
- A noncancerous pituitary tumor, an uncommon cause
A family history of thyroid or autoimmune disease raises the risk. For Graves’ disease specifically, the NIDDK also lists other autoimmune disorders and nicotine use as risk factors, and notes it is more common in women and in people older than 30.
Symptoms
Typical signs include weight loss despite a normal or increased appetite, heart palpitations, hand tremors, nervousness, heat intolerance, and excessive sweating. Other symptoms include fatigue, muscle weakness, sleep disturbances, mood swings, faster bowel movements, and a visible goiter in the neck.
Graves’ disease can also affect the eyes. More than 1 in 3 people with Graves’ disease develop Graves’ ophthalmopathy, which can cause bulging eyes (exophthalmos), gritty or irritated eyes, light sensitivity, eye pressure or pain, and blurred or double vision.
Diagnosis
Diagnosis relies on a blood test for TSH, which is low, along with free T4 and T3, which are elevated. As the American Thyroid Association puts it, lab results in hyperthyroidism usually show high T4 and/or T3 and low TSH.
Testing for TSH receptor antibodies (TRAb) or thyroid stimulating immunoglobulin (TSI) confirms Graves’ disease. A thyroid ultrasound, a radioactive iodine uptake test, and sometimes a thyroid scan round out the workup to pinpoint the exact cause and guide treatment.
Available treatments
Several treatment options exist depending on the cause and severity:
- Antithyroid medications (methimazole, propylthiouracil) to slow hormone production. Treatment typically runs 1 to 2 years, and sometimes longer.
- Beta blockers to relieve symptoms such as rapid heart rate, shakiness, and nervousness. They control symptoms but do not treat the underlying overactivity.
- Radioactive iodine to destroy part of the overactive thyroid tissue. Almost all patients are treated with a single dose, though about 10% may need a second one.
- Surgery (thyroidectomy) for a large goiter or when other treatments haven’t worked.
- Regular endocrinology follow-up with blood work. Treatment can lead to hypothyroidism, which is then managed with thyroid hormone replacement.
Complications
Untreated or poorly controlled hyperthyroidism can lead to heart problems, including a fast heart rate, abnormal heart rhythm, and heart failure. It can also cause osteoporosis. Thyroid storm (also called thyroid crisis) is a sudden worsening of symptoms that may occur with infection or stress and needs emergency care. Untreated Graves’ eye disease can lead to corneal ulcers, double vision, and vision loss.
Prevention
There’s no specific way to prevent autoimmune hyperthyroidism, but regular medical follow-up allows for early detection, especially if you have a family history. Avoid self-medicating with iodine supplements, since too much iodine is itself a cause. Tell your doctor about any thyroid hormone treatment before changing the dose, and let them know if you use nicotine, which raises the risk of Graves’ disease and its eye complications.
When should you see a doctor?
See a doctor for unexplained weight loss, palpitations, tremors, or unusual nervousness. Untreated hyperthyroidism can lead to heart complications, including abnormal heart rhythm and heart failure. Seek urgent care if symptoms worsen suddenly alongside a fever or an infection, which can signal a thyroid storm. If in doubt, don’t hesitate to consult a doctor quickly.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Hyperthyroidism, official U.S. data and guidance
- NIDDK: Graves’ Disease, causes, risk factors, and treatment
- American Thyroid Association: Hyperthyroidism, patient education from the U.S. learned society
- MedlinePlus: Hyperthyroidism, U.S. National Library of Medicine health information
- MedlinePlus Medical Encyclopedia: Hyperthyroidism, symptoms, diagnosis, and complications
- StatPearls (NCBI Bookshelf, NIH): Hyperthyroidism, prevalence in women compared with men (Whickham Survey)