Is anyone else out there racing with thyroid problems? I have been getting treatment for the last 4 years or so and after an initial significant improvement after many years of never seeming to get anywhere I have dropped back a lot with only occasional better performances. My Doc is pretty good but doesn't necessarily understand a runners perspective on this issue such as referring current medication to resting heart rate and as long as my blood tests come back in what seems to be a broad range of 'normal' he is reluctant to see a need for changes to my dosage. The medication affects my metabolism and if my RHR strays consistently outside the range of 48-52 I know its not quite right. I know one local runner who has the same medical problem but he is actually very good and doesn't seem to have the same difficulties with it as I have. To give an idea when the treatment was going well I ran Anniversary Waltz in 2.09 - this year I think I was about 2.35. Its pretty frustrating! Is anyone else dealing with this and in particular does anyone change their medication according to activity levels? I'm convinced the same dose every day cant be right for days when you do nothing and others when I might be running for five hours, but I'm told its a background thing rather than something you can or need to alter such as the amount of food you eat or (for example) insulin dosage for someone with diabetes.