Hyperthyroidism (overactive thyroid) occurs when your thyroid gland produces too much of the hormone thyroxine. Hyperthyroidism can accelerate your body's metabolism, causing unintentional weight loss and a rapid or irregular heartbeat.
Several treatments are available for hyperthyroidism. Doctors use anti-thyroid medications and radioactive iodine to slow the production of thyroid hormones. Sometimes, hyperthyroidism treatment involves surgery to remove all or part of your thyroid gland.
Although hyperthyroidism can be serious if you ignore it, most people respond well once hyperthyroidism is diagnosed and treated.
Hyperthyroidism can mimic other health problems, which can make it difficult for your doctor to diagnose. It can also cause a wide variety of signs and symptoms, including:
- Unintentional weight loss, even when your appetite and food intake stay the same or increase
- Rapid heartbeat (tachycardia) — commonly more than 100 beats a minute
- Irregular heartbeat (arrhythmia)
- Pounding of your heart (palpitations)
- Increased appetite
- Nervousness, anxiety and irritability
- Tremor — usually a fine trembling in your hands and fingers
- Changes in menstrual patterns
- Increased sensitivity to heat
- Changes in bowel patterns, especially more frequent bowel movements
- An enlarged thyroid gland (goiter), which may appear as a swelling at the base of your neck
- Fatigue, muscle weakness
- Difficulty sleeping
- Skin thinning
- Fine, brittle hair
Older adults are more likely to have either no signs or symptoms or subtle ones, such as an increased heart rate, heat intolerance and a tendency to become tired during ordinary activities.
Hyperthyroidism can be caused by a number of conditions, including Graves' disease, Plummer's disease and thyroiditis.
Your thyroid is a small, butterfly-shaped gland at the base of your neck, just below your Adam's apple. The thyroid gland has an enormous impact on your health. Every aspect of your metabolism is regulated by thyroid hormones.
Your thyroid gland produces two main hormones, thyroxine (T4) and triiodothyronine (T3), that influence every cell in your body. They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate, and help regulate the production of protein. Your thyroid also produces a hormone that helps regulate the amount of calcium in your blood (calcitonin).
Health care professionals use thyroid tests to check how well your thyroid is working and to find the cause of problems such as hyperthyroidism or hypothyroidism. The thyroid makes two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid hormones control how the body uses energy, so they affect nearly every organ in your body, even your heart.
What blood tests do doctors use to check thyroid function?
Doctors may order one or more blood tests to check your thyroid function. Tests may include thyroid stimulating hormone (TSH), T4, T3, and thyroid antibody tests.
For these tests, a health care professional will draw blood from your arm and send it to a lab for testing. Your doctor will talk to you about your test results.
Health care professionals usually check the amount of TSH in your blood first. TSH is a hormone made in the pituitary gland that tells the thyroid how much T4 and T3 to make.
A high TSH level most often means you have hypothyroidism, or an underactive thyroid. This means that your thyroid isn’t making enough hormone. As a result, the pituitary keeps making and releasing TSH into your blood.
A low TSH level usually means you have hyperthyroidism, or an overactive thyroid. This means that your thyroid is making too much hormone, so the pituitary stops making and releasing TSH into your blood.
If the TSH test results are not normal, you will need at least one other test to help find the cause of the problem.
A high blood level of T4 may mean you have hyperthyroidism. A low level of T4 may mean you have hypothyroidism.
In some cases, high or low T4 levels may not mean you have thyroid problems. If you are pregnant or are taking oral contraceptives , your thyroid hormone levels will be higher. Severe illness or using corticosteroids—medicines to treat asthma, arthritis, skin conditions, and other health problems—can lower T4 levels. These conditions and medicines change the amount of proteins in your blood that “bind,” or attach, to T4. Bound T4 is kept in reserve in the blood until it’s needed. “Free” T4 is not bound to these proteins and is available to enter body tissues. Because changes in binding protein levels don’t affect free T4 levels, many healthcare professionals prefer to measure free T4.
If your health care professional thinks you may have hyperthyroidism even though your T4level is normal, you may have a T3 test to confirm the diagnosis. Sometimes T4 is normal yet T3is high, so measuring both T4 and T3 levels can be useful in diagnosing hyperthyroidism.