@carrotisland: There are several signs and/or symptoms of thyroid trouble. If you experience sudden weight loss, tremors, sweating, increased appetite, palpitations, fatigue, menstrual problems, or swelling at the base of your neck, it could be a sign of hyperthyroidism.
There is also what is called hypothyroidism. Several of the symptoms are the same as hyperthyroidism such as fatigue, tremors, and menstrual problems. However, with hypothyroidism, weight gain, hair loss, low temperature, depression, and constipation are issues.
If you are experiencing any of these symptoms, you should see your doctor.