hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones that circulate in the blood ("hyper" means "over" in greek). thyrotoxicosis is a toxic condition that is caused by an excess of thyroid hormones from any cause. thyrotoxicosis can be caused by an excessive intake of thyroid hormone or by overproduction of thyroid hormones by the thyroid gland.
what is hyperthyroidism?