Levothyroxine http://www.nlm.nih.gov/medlineplus/d...r/a682461.html
Why is this medication prescribed?
Levothyroxine, a thyroid hormone, is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Without this hormone, the body cannot function properly, resulting in poor growth, slow speech, lack of energy, weight gain, hair loss, dry thick skin, and increased sensitivity to cold. When taken correctly, levothyroxine reverses these symptoms. Levothyroxine is also used to treat congenital hypothyroidism (cretinism) and goiter (enlarged thyroid gland).
In regards to heart problems ... usually you can get a racing heart by having too much thyroid.
If you are Hypo you will need to take it ... as it will suppliment for the thyroid your body is not making. Did he tell you you blood test results for TSH, T4, T3 and RT3? I have taken supplimental thyroid for hypo for over ten years. The main thing is to keep on top of things. Make sure you get your blood tested regularly and write down all of your symptoms.
Side Note - I have Hasimotos of which is an auto-immune disorder that causes your body to attack the thyroid produce by the body.