I was diagnosed with Hypothyroidism 2 years ago and originally I ...

I was diagnosed with Hypothyroidism 2 years ago and originally I was prescribed synthroid. I was tired and cold all the time. I was switched by my doctor to Levoxyl 50 mcg about a year ago. I am only 10 lbs overweight I still have not been able to lose. Over the last 4 months I trained and and completed a 26.2 mile marathon and 3 different 13.1 miles half marathons (running) I have not lost any weight. My enodocrinologist has recommended that I get checked again to see if the dosage needs adjustment. I have a feeling it is too high.I have recently had some symptoms such as hot and cold flashes, headaches, heart palpitations. I have more energy now than ever in my life. Other than the hypothyroidism I am healthy and should not have heart palpitations. and my endo says that the amount of running may have shocked my body into working more efficiently. I am to be tested in a few weeks. I don't know if this is true but I also heard that if you buy medications that are on the shelf too long that they lose some of their potency.