Hyperthyroidism occurs when the thyroid gland is over-active, though this condition can arise in a variety of ways:
- Graves' disease is the most common cause of overproduction of thyroid hormone and can result in enlargement of the gland. Other symptoms include sleep problems, irritability, muscle weakness and a rapid heartbeat.
- Toxic adenomas are benign thyroid gland tumours. Adenomas, or nodules, develop within the thyroid gland and start to secrete thyroid hormones, thus disturbing your body's delicate chemical balance. A goiter may sometimes contain a number of individual nodules.
- Sub-acute thyroiditis causes an inflammation of the thyroid, which feels tender. This condition, which is possibly the result of a viral infection, causes the thyroid gland to leak excess hormones, resulting in a temporary hyperthyroidism, which usually lasts for only a few weeks.
- Pituitary gland disorders or cancerous growths within the thyroid gland, although considered extremely rare, can also result in hyperthyroidism.