I think she probably meant that your TSH is high, as Scottie said.
TSH stands for thyroid stimulating hormone. When your thyroid is sluggish (hypo), your body produces more TSH to try to get it moving. Therefore, a high TSH means you are hypothyroid (it's like your body is screaming, "GET WORKING!!!" at your thyroid).
For those of us with AI issues, it is especially important to stay on the lower end of the normal range. Most people feel best with a TSH lower than 2. For me, it needs to be between .3 and 1.5. Any higher, and I have symptoms.
Here are the AACE recommendations for TSH levels: http://www.aace.com/public/awareness/tam/2003/explanation.php
A fantastic resource for reading up on thyroid problems is www.thyroid.about.com
but it's produced by a patient advocate, not a doctor. As such, you'll want to find research to back up anything you find there before sharing it with your doctor. My doctor loves when I bring in AACE information, because they are doctors; I would never even try to bring in something from thyroid.about.com because I know it wouldn't go over well. Fortunately, the articles on the site are usually pretty good about citing sources.