Hyperthyroidism means that your body has too much thyroid hormone, which controls how your body uses energy. Too much thyroid hormone can make you lose weight quickly, have a fast heartbeat, sweat a lot, or feel nervous and moody. If it isn't treated, it can cause serious problems.
Medical Review:Adam Husney MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Kathleen Romito MD - Family Medicine & David C.W. Lau MD, PhD, FRCPC - Endocrinology