Reader: I am a woman in my early 60s. Since age 12 or so, I could feel my heart pounding and racing. During treatment at a hospital, I set off the heart monitor. I am sending my latest thyroid test results and the Holter monitor test results.

Dr. Zipes: Your thyroid results indicate an under-acting thyroid (hypothyroid). The Holter test shows your heart rate varied between 52 and 129 beats per minute in 24 hours. This is not at all unusual, as during sleep your heart rate slows, and during activity it speeds. I would like to see the ECG strips that set off the alarm during your hospitalization. They may provide more insight into what is causing your palpitations than did the Holter test.