Understanding TSH Levels and Weight Management

Question
Back in December I got a Wii Fit and noticed that my weight was increasing almost daily.  On January 7th I decided that I needed to lose weight, so I began watching what I was eating closely and exercising more frequently.  Over the next couple of months I went from 191 to 163, then I started gaining weight.  My weight is now 166 and I eat about 1500 calories a day and exercise 1 to 1.5 hours six days a week.  I do a variety of exercises from running to water aerobics.  I am a female 5'7" tall.

Last week I went for my annual physical and mentioned my weight plateau and was told that my TSH would be looked at.  When the lab work returned my TSH was at 3.41.  I began to do some Internet research and see that some endocrinologists look at any level over 3.0 to be abnormal.  I called my former doctor that I went to before I moved and here are my prior TSH levels:
Oct 2002 1.91
Oct 2004 2.45
Dec 2006 2.57
Apr 2009 3.291
Apr 2010 3.410

Over the past 5 years or so I have not been able to get my weight below 160.  I just assumed that I was not working hard enough to get it down, but when I consider what I am currently eating and the amount of exercise I am doing, and in light of the TSH levels shown above, I am concerned that there could be a thyroid issue.

I'm not looking for a "magic pill" to make it easy to lose weight.  In fact, my doctor suggested that she prescribe diet pills for a month or so to help speed up my metabolism, but I don't want to do that.  I just want to be assured that the increasing thyroid numbers and the difficulty in losing weight are not an indication that there is a problem that needs to be checked on.

Thank you so much for any help you can provide!

Answer
Hi Jennifer.  Your TSH result of 3.410 is generally considered as "borderline normal".  Like you researched, some doctors will say it's normal and some will say it's abnormal.  I think the next step would be for you to possibly have further testing.  The TSH blood test is not the only test to diagnose thyroid disease.  Perhaps you can follow-up with your doctor.

Samantha