Thyroidgland is a small, butterfly-shaped gland located at the front of your neck. It produces 2 hormones ie: tetraiodothyronine (T4) and triiodothyronine (T3), which are the two primary hormones that control how a cells use energy.
Hyperthyroidism occurs when the thyroid makes too much T4, T3, or both. Diagnosis of overactive thyroid and treatment of the underlying cause can relieve symptoms and prevent complications.
Graves' disease. Graves' disease is an autoimmune disorder in which antibodies produced by your immune system stimulate your thyroid to produce too much T4. It's the most common cause of hyperthyroidism.
Hyperfunctioning thyroid nodules (toxic adenoma, toxic multinodular goiter or Plummer's disease). This form of hyperthyroidism occurs when one or more adenomas of your thyroid produce too much T4. An adenoma is a part of the gland that has walled itself off from the rest of the gland, forming noncancerous (benign) lumps that may cause an enlargement of the thyroid.
Thyroiditis. Sometimes thyroid gland can become inflamed, due to an autoimmune condition or for unknown reasons. The inflammation can cause excess thyroid hormone stored in the gland to leak into your bloodstream. Some types of thyroiditis may cause pain, while others are painless.
Other causes of hyperthyroidism include:
tumors of the ovaries or testes
benign tumors of the thyroid or pituitary gland
large amounts of tetraiodothyronine taken through dietary supplements or medication
Symptoms of hyperthyroidism
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, person may experience a rapid heart rate, elevated blood pressure, and hand tremors patient may also sweat a lot and develop a low tolerance for heat. Hyperthyroidism can cause more frequent bowel movements, weight loss, and, in women, irregular menstrual cycles.