Hyperthyroidism sometimes looks like other health problems. That can make it hard to diagnose. It can cause many symptoms, including:

• Losing weight without trying.
• Fast heartbeat, a condition called tachycardia.
• Irregular heartbeat, also called arrhythmia.
• Pounding of the heart, sometimes called heart palpitations.
• Increased hunger.
• Nervousness, anxiety and irritability.
• Tremor, usually a small trembling in the hands and fingers.
• Sweating.
• Changes in menstrual cycles.
• Increased sensitivity to heat.
• Changes in bowel patterns, especially more-frequent bowel movements.
• Enlarged thyroid gland, sometimes called a goiter, which may appear as a swelling at the base of the neck.
• Tiredness.
• Muscle weakness.
• Sleep problems.
• Warm, moist skin.
• Thinning skin.
• Fine, brittle hair.

Older adults are more likely to have symptoms that are hard to notice. These symptoms may include an irregular heartbeat, weight loss, depression, and feeling weak or tired during ordinary activities.

When to see a doctor

If you lose weight without trying, or if you notice a rapid heartbeat, unusual sweating, swelling at the base of your neck or other symptoms of hyperthyroidism, make an appointment with your health care provider. Tell your provider about all the symptoms you've noticed even if they are minor.

After a diagnosis of hyperthyroidism, most people need regular follow-up visits with their health care provider to monitor the condition.

Hyperthyroidism can be caused by several medical conditions that affect the thyroid gland. The thyroid is a small, butterfly-shaped gland at the base of the neck. It has a big impact on the body. Every part of metabolism is controlled by hormones that the thyroid gland makes.

The thyroid gland produces two main hormones: thyroxine (T-4) and triiodothyronine (T-3). These hormones affect every cell in the body. They support the rate at which the body uses fats and carbohydrates. They help control body temperature. They have an effect on heart rate. And they help control how much protein the body makes.

Hyperthyroidism happens when the thyroid gland puts too much of those thyroid hormones into the bloodstream. Conditions that can lead to hyperthyroidism include:

• Graves' disease. Graves' disease is an autoimmune disorder that causes the immune system to attack the thyroid gland. That prompts the thyroid to make too much thyroid hormone. Graves' disease is the most common cause of hyperthyroidism.
• Overactive thyroid nodules. This condition also is called toxic adenoma, toxic multinodular goiter and Plummer disease. This form of hyperthyroidism happens when a thyroid adenoma makes too much thyroid hormone. An adenoma is a part of the gland that is walled off from the rest of the gland. It forms noncancerous lumps that can make the thyroid bigger than usual.
• Thyroiditis. This condition happens when the thyroid gland becomes inflamed. In some cases, it's due to an autoimmune disorder. In others, the reason for it is unclear. The inflammation can cause extra thyroid hormone stored in the thyroid gland to leak into the bloodstream and cause symptoms of hyperthyroidism.

Risk factors for hyperthyroidism include:

• A family history of thyroid disease, particularly Graves' disease.
• A personal history of certain chronic illnesses, including pernicious anemia and primary adrenal insufficiency.
• A recent pregnancy, which raises the risk of developing thyroiditis. This can lead to hyperthyroidism.

Hyperthyroidism can lead to the following complications.

Heart problems

Some of the most serious complications of hyperthyroidism involve the heart, including:

• A heart rhythm disorder called atrial fibrillation that increases the risk of stroke.
• Congestive heart failure, a condition in which the heart can't circulate enough blood to meet the body's needs.

Brittle bones

Untreated hyperthyroidism can lead to weak, brittle bones. This condition is called osteoporosis. The strength of bones depends, in part, on the amount of calcium and other minerals in them. Too much thyroid hormone makes it hard for the body to get calcium into bones.

Vision problems

Some people with hyperthyroidism develop a problem called thyroid eye disease. It's more common in people who smoke. This disorder affects the muscles and other tissues around the eyes.

Symptoms of thyroid eye disease include:

• Bulging eyes.
• Gritty sensation in the eyes.
• Pressure or pain in the eyes.
• Puffy or retracted eyelids.
• Reddened or inflamed eyes.
• Light sensitivity.
• Double vision.

Eye problems that go untreated may cause vision loss.

Discolored, swollen skin

In rare cases, people with Graves' disease develop Graves' dermopathy. This causes the skin to change colors and swell, often on the shins and feet.

Thyrotoxic crisis

This rare condition also is called thyroid storm. Hyperthyroidism raises the risk of thyrotoxic crisis. It causes severe, sometimes life-threatening symptoms. It requires emergency medical care. Symptoms may include:

• Fever.
• Fast heartbeat.
• Nausea.
• Vomiting.
• Diarrhea.
• Dehydration.
• Confusion.
• Delirium.

Hyperthyroidism is diagnosed with a medical history, physical exam and blood tests. Depending on the results of the blood tests, you may need other tests too.

• Medical history and physical exam. During the exam, your health care provider may check for:

  • Slight tremor in your fingers and hands.
  • Overactive reflexes.
  • Rapid or irregular pulse.
  • Eye changes.
  • Warm, moist skin.

  Your provider also examines your thyroid gland as you swallow to see if it's larger than usual, bumpy or tender.

• Blood tests. Blood tests that measure the hormones T-4 and T-3 and thyroid-stimulating hormone (TSH) can confirm a diagnosis of hyperthyroidism. A high level of T-4 and a low level of TSH is common in people with hyperthyroidism.

  Blood tests are particularly important for older adults because they may not have classic symptoms of hyperthyroidism.

  Thyroid blood tests may give false results if you take biotin. Biotin is a B vitamin supplement that also may be found in multivitamins. Tell your health care provider if you are taking biotin or a multivitamin with biotin. To make sure your blood test is accurate, your health care provider may ask you to stop taking biotin 3 to 5 days before the test.

If blood test results show hyperthyroidism, your health care provider may suggest one of the following tests. They can help find out why your thyroid is overactive.

• Radioiodine scan and uptake test. For this test, you take a small, dose of radioactive iodine, called radioiodine, to see how much of it collects in your thyroid gland and where it collects in the gland.

  If your thyroid gland takes in a high amount of radioiodine, that means your thyroid gland is making too much thyroid hormone. The most likely cause is either Graves' disease or overactive thyroid nodules.

  If your thyroid gland takes in a low amount of radioiodine, that means hormones stored in the thyroid gland are leaking into the bloodstream. In that case, it's likely that you have thyroiditis.

• Thyroid ultrasound. This test uses high-frequency sound waves to make images of the thyroid. Ultrasound may be better at finding thyroid nodules than are other tests. There's no exposure to radiation with this test, so it can be used for people who are pregnant or breastfeeding, or others who can't take radioiodine.

There are several treatments available for hyperthyroidism. The best approach for you depends on your age and health. The underlying cause of hyperthyroidism and how severe it is make a difference too. Your personal preference also should be considered as you and your health care provider decide on a treatment plan. Treatment may include:

• Anti-thyroid medicine. These medications slowly ease symptoms of hyperthyroidism by preventing the thyroid gland from making too many hormones. Anti-thyroid medications include methimazole and propylthiouracil. Symptoms usually begin to improve within several weeks to months.

  Treatment with anti-thyroid medicine typically lasts 12 to 18 months. After that, the dose may be slowly decreased or stopped if symptoms go away and if blood test results show that thyroid hormone levels have returned to the standard range. For some people, anti-thyroid medicine puts hyperthyroidism into long-term remission. But other people may find that hyperthyroidism comes back after this treatment.

  Although rare, serious liver damage can happen with both anti-thyroid medications. But because propylthiouracil has caused many more cases of liver damage, it's generally used only when people can't take methimazole. A small number of people who are allergic to these medicines may develop skin rashes, hives, fever or joint pain. They also can raise the risk of infection.

• Beta blockers. These medicines don't affect thyroid hormone levels. But they can lessen symptoms of hyperthyroidism, such as a tremor, rapid heart rate and heart palpitations. Sometimes, health care providers prescribe them to ease symptoms until thyroid hormones are closer to a standard level. These medicines generally aren't recommended for people who have asthma. Side effects may include fatigue and sexual problems.
• Radioiodine therapy. The thyroid gland takes up radioiodine. This treatment causes the gland to shrink. This medicine is taken by mouth. With this treatment, symptoms typically lessen within several months. This treatment usually causes thyroid activity to slow enough to make the thyroid gland underactive. That condition is hypothyroidism. Because of that, over time, you may need to take medicine to replace thyroid hormones.

• Thyroidectomy. This is surgery to remove part of or all of the thyroid gland. It is not used often to treat hyperthyroidism. But it may be an option for people who are pregnant. It also may be a choice for those who can't take anti-thyroid medicine and don't want to or can't take radioiodine therapy.

  Risks of this surgery include damage to the vocal cords and parathyroid glands. The parathyroid glands are four tiny glands on the back of the thyroid. They help control the level of calcium in the blood.

  People who have a thyroidectomy or radioiodine therapy need lifelong treatment with the medicine levothyroxine (Levoxyl, Synthroid, others). It supplies the body with thyroid hormones. If the parathyroid glands are removed during surgery, medicine also is needed to keep blood calcium in a healthy range.

Thyroid eye disease

If you have thyroid eye disease, you may be able to manage mild symptoms with self-care steps, such as artificial tear drops and lubricating eye gels. Avoiding wind and bright lights can help too.

More-severe symptoms may need treatment with medicine called corticosteroids, such as methylprednisolone or prednisone. They can lessen swelling behind the eyeballs. The medicine teprotumumab (Tepezza) also may be used to control moderate to severe symptoms. If those medicines don't ease symptoms, other medicines are sometimes used to treat thyroid eye disease. They include, tocilizumab (Actemra), rituximab (Rituxan) and mycophenolate mofetil (Cellcept).

In some cases, surgery may be needed to treat thyroid eye disease, including:

• Orbital decompression surgery. In this surgery, the bone between the eye socket and the sinuses is removed. This surgery can improve vision. It also gives the eyes more room, so they can go back to their usual position. There is a risk of complications with this surgery. If you have double vision before the surgery, it may not go away afterward. Some people develop double vision after the surgery.
• Eye muscle surgery. Sometimes scar tissue from thyroid eye disease can cause one or more eye muscles to be too short. This pulls the eyes out of alignment, causing double vision. Eye muscle surgery may correct double vision by cutting the muscle from the eyeball and attaching it again farther back.

Once you begin treatment, symptoms of hyperthyroidism likely will get better. Along with your treatment, your health care provider might suggest that you reduce iodine in your diet. It can make hyperthyroidism worse. Kelp, dulse and other types of seaweed contain a lot of iodine. Cough syrup and multivitamins also may contain iodine.

Graves' disease

If you have Graves' disease that causes eye or skin problems, taking the following steps may help ease symptoms:

• Don't smoke. Smoking has been linked to the development of thyroid eye disease. It also can make that condition worse. And smoking can cause symptoms to come back after treatment.
• Keep your eyes lubricated. Eye drops may help relieve dryness and scratchiness. A cool compress also can provide moisture. If your eyes don't completely close, a lubricating gel at bedtime may help keep the cornea from drying out. Some people also tape their eyelids shut while they sleep.
• Protect your eyes. Wear sunglasses to help protect your eyes from the sun and wind.
• Keep your head up. Raising the head of your bed may lessen swelling and ease pressure on your eyes.
• Use creams for swollen skin. Creams containing hydrocortisone that you can buy without a prescription (Cortizone 10, others) may help ease swollen skin on the shins and feet. For help finding these creams, ask a pharmacist.

If you've been diagnosed with hyperthyroidism, it's important that you get the medical care you need. After you and your health care provider have decided on a treatment plan, there also are some things you can do to cope with the condition and help your body heal.

• Get regular exercise. Exercise can help you feel better. It improves muscle tone and helps keep your heart and lungs healthy. Exercise also can help you feel more energetic.
• Learn relaxation techniques. Many relaxation techniques can help you keep a positive outlook, especially when coping with illness. Research has shown that for Graves' disease in particular, stress is a risk factor. Learning to relax and find a sense of calm may help sustain your physical and mental well-being.

You'll likely start by seeing your primary care provider. But you may be referred directly to a specialist in hormone disorders, called an endocrinologist. If you have eye problems, you may be referred to an eye doctor, also called an ophthalmologist.

Here's some information to help you get ready for your appointment and to know what to expect from your health care provider.

What you can do

• Be aware of any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do to get ready for it, such as not eat or drink for a certain amount of time.
• Write down any symptoms you have, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medicines, vitamins or supplements you're taking, especially any supplements or vitamins containing biotin.
• Take a family member or friend along, if possible. Someone who is there with you may remember information you missed or forgot.
• Write down questions to ask your health care provider.

Writing a list of questions will help you make the most of your time with your health care provider. For hyperthyroidism, some questions to ask include:

• What's the most likely cause of my symptoms?
• Are there other possible causes?
• What tests do I need?
• Is my condition likely temporary or long lasting?
• What treatment options are available, and which do you recommend for me?
• I have other health conditions. How can I manage these conditions together?
• Should I see a specialist?
• Is there a generic alternative to the medicine you're prescribing?
• Do you have brochures or other printed material I can take? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your health care provider is likely to ask you some questions, including:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, makes your symptoms better?
• What, if anything, makes your symptoms worse?
• Do members of your family have thyroid disease?
• Have you had any recent radiology scans that used intravenous contrast?