Hyperthyroidism (overactive thyroid) is a condition in which your thyroid gland produces too much of the hormone thyroxine. Hyperthyroidism can accelerate your body’s metabolism significantly, causing sudden weight loss, a rapid or irregular heartbeat, sweating, and nervousness or irritability.
Several treatment options are available if you have hyperthyroidism. Doctors use anti-thyroid medications and radioactive iodine to slow the production of thyroid hormones. Sometimes, treatment of hyperthyroidism 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.
A variety of conditions can cause hyperthyroidism. Graves’ disease, an autoimmune disorder, is the most common cause of hyperthyroidism. It causes antibodies to stimulate the thyroid to secrete too much hormone. Graves’ disease occurs more often in women than in men. It tends to run in families, which suggests a genetic link. You should tell your doctor if your relatives have had the condition.
Other causes of hyperthyroidism can include:
- excess iodine, a key ingredient in T4 and T3
- inflammation of the thyroid (thyroiditis) that causes T4 and T3 to leak out of the gland
- tumors of the ovaries or testes
- benign tumors of the thyroid or pituitary gland
- large amounts of tetraiodothyronine taken through dietary supplements or medication
Any process that causes an increase in the peripheral circulation of unbound thyroid hormone can cause signs and symptoms of hyperthyroidism. Disturbances of the normal homeostatic mechanism can occur at the level of the hypothalamus, the pituitary gland and the thyroid gland, as illustrated in diagram above.
Defect of hypothalamus and pituitary gland can be hyper-secreting of hormone which can induce excessive secretion of thyroid hormone causing hyperthyroidism. But this is rare. Hyper-secretion may be due to certain tumor or any other defects. On investigation, this defect can increase level of tri-iodothyronine (T3) and level of thyroxine (T4) in plasma. Level of Thyroid Releasing Hormone (TRH) and/or level of Thyroid Stimulating Hormone (TSH) also may be increased. Goiter that is enlargement of thyroid gland may be present.
Defect also can be originated from the thyroid gland itself. Hyper-secreting of thyroid hormone may be one of the causes with absent of goitre. Other than that, is Graves’s Disease which is the common cause of hyperthyroidism. Graves’s Disease is an autoimmune disease in which the body abnormally produces thyroid-stimulating immunoglobulin (TSI), an antibody whose targeting the TSH receptor on the thyroid cells. TSI will stimulates both secretion and growth of the thyroid in a manner similar to TSH.
High amounts of T4, T3, or both can cause an excessively high metabolic rate. This is called a hypermetabolic state. When in a hypermetabolic state, you may experience a rapid heart rate, elevated blood pressure, and hand tremors. You may also develop a low tolerance for heat and sweat a lot. Hyperthyroidism can cause more frequent bowel movements, weight loss, and, in women, irregular menstrual cycles.
Visibly, the thyroid gland itself can swell into a goiter, which can be either symmetrical or one-sided. Your eyes may also appear quite prominent, which is a sign of exophthalmos, a condition that’s related to Graves’ disease.
Other symptoms of hyperthyroidism include:
- increased appetite
- inability to concentrate
- irregular heartbeat
- difficulty sleeping
- fine, brittle hair
- hair loss
- nausea and vomiting
- breast development in men
The following symptoms require immediate medical attention:
- shortness of breath
- loss of consciousness
- fast, irregular heart rate
Hyperthyroidism can also cause atrial fibrillation, a dangerous arrhythmia that can lead to strokes, as well as congestive heart failure.
Measurement of the TSH level is the only initial test necessary in a patient with a possible diagnosis of hyperthyroidism without evidence of pituitary disease. Further testing is warranted if the TSH level is abnormal. An undetectable TSH level is diagnostic of hyperthyroidism. Antithyroid antibodies are elevated in Graves’ disease and lymphocytic thyroiditis but usually are not necessary to make the diagnosis. Thyroid-stimulating antibody levels can be used to monitor the effects of treatment with antithyroid drugs in patients with Graves’ disease. Radionuclide uptake and scan easily distinguishes the high uptake of Graves’ disease from the low uptake of thyroiditis and provides other useful anatomic information. Nonspecific laboratory findings can occur in hyperthyroidism, including anemia, granulocytosis, lymphocytosis, hypercalcemia, transaminase elevations, and alkaline phosphatase elevation.
Several treatments for hyperthyroidism exist. The best approach for you depends on your age, physical condition, the underlying cause of the hyperthyroidism, personal preference and the severity of your disorder:
- Radioactive iodine. Taken by mouth, radioactive iodine is absorbed by your thyroid gland, where it causes the gland to shrink and symptoms to subside, usually within three to six months. Because this treatment causes thyroid activity to slow considerably, causing the thyroid gland to be underactive (hypothyroidism), you may eventually need to take medication every day to replace thyroxine. Used for more than 60 years to treat hyperthyroidism, radioactive iodine has been shown to be generally safe.
- Anti-thyroid medications. These medications gradually reduce symptoms of hyperthyroidism by preventing your thyroid gland from producing excess amounts of hormones. They include propylthiouracil and methimazole (Tapazole). Symptoms usually begin to improve in six to 12 weeks, but treatment with anti-thyroid medications typically continues at least a year and often longer. For some people, this clears up the problem permanently, but other people may experience a relapse. Both drugs can cause serious liver damage, sometimes leading to death. Because propylthiouracil has caused far more cases of liver damage, it generally should be used only when you can’t tolerate methimazole. A small number of people who are allergic to these drugs may develop skin rashes, hives, fever or joint pain. They also can make you more susceptible to infection.
- Beta blockers. These drugs are commonly used to treat high blood pressure. They won’t reduce your thyroid levels, but they can reduce a rapid heart rate and help prevent palpitations. For that reason, your doctor may prescribe them to help you feel better until your thyroid levels are closer to normal. Side effects may include fatigue, headache, upset stomach, constipation, diarrhea or dizziness.
- Surgery (thyroidectomy). If you’re pregnant or otherwise can’t tolerate anti-thyroid drugs and don’t want to or can’t have radioactive iodine therapy, you may be a candidate for thyroid surgery, although this is an option in only a few cases.
In a thyroidectomy, your doctor removes most of your thyroid gland. Risks of this surgery include damage to your vocal cords and parathyroid glands — four tiny glands situated on the back of your thyroid gland that help control the level of calcium in your blood. In addition, you’ll need lifelong treatment with levothyroxine (Levoxyl, Synthroid, others) to supply your body with normal amounts of thyroid hormone. If your parathyroid glands also are removed, you’ll need medication to keep your blood-calcium levels normal.