The thyroid is a butterfly-shaped organ located in the center of the neck. It produces hormone controlling speed of one's metabolism. When a person's thyroid does not work properly the person most likely to experience the following symptoms: Change in weight, Neck swelling, heart rate changes, mood swings, hair loss, feeling too cold or hot. For hypothyroidism one can experience dry skin, brittle nails, numbness in the hands, constipation, abnormal menstrual periods. For hyperthyroidism includes muscle weakness, vision problems,diarrhea and irregular menstrual period.