Current statistics in the United States estimate that hyperthyroidism, the excessive production of thyroid hormone, affects as many as 2 percent of women and less than 1 percent of men. There are nine disorders that lead to hyperthyroidism, and it is caused by many different conditions. The symptoms of hyperthyroidism include those of a metabolism that is speeding up. A racing heart, nervousness, increased transit time through the gut (which causes an increase in bowel movements), trembling hands, weakness, and weight loss are some of the common symptoms that may be experienced.