Hyperthyroidism, also called overactive thyroid or thyrotoxicosis, occurs when the thyroid gland produces much more hormones than the body needs. Hyperthyroidism increases the body's metabolism, causing sudden weight loss, a rapid or irregular heartbeat, sweating, decreased menstrual flow and nervousness or irritability. Without treatment, hyperthyroidism can lead to serious heart problems, bone problems and a dangerous condition called thyroid storm.
Attribution: Straight Talk Foundation