Hyperthyroidism is a thyroid condition in which the thyroid gland is overactive and produces an excess of thyroid hormone. The thyroid gland is a small organ in the front of your neck. It is more common in women than in men, and it is thought to have a genetic component. When the thyroid gland is overactive (hyperthyroidism), the body’s processes speed up, causing nervousness, anxiety, mood swings, rapid heartbeat, hand tremor, excessive sweating, weight loss, and sleep problems, among other symptoms. Hyperthyroidism is characterized by increased thyroid hormone production by the thyroid gland, and it is also known as thyrotoxicosis.