Also will add that fasting glucose is not a good indicator. you need to ask your doctor to test HA1c. THis test gives average glucose levels over a 3 month period and is a very indication of your blood sugar levels and status.
Thyroid being off can affect your glucose. However as Zoela said take this as a timely warning about there being a potential problem and use it.
Best Wishes
Being diagnosed as pre-diabetic is an excellent opportunity to make some changes in your lifestyle that will postpone or prevent advancing to diabetes. First off you need to get your thyroid under control so that you can lose the weight you need to. The best way to reduce blood sugar is to maintain normal weight, reduce carb intake and get regular exercise. Do continue to have your blood sugar tested on a regular basis. Also, keep in mind down the road that if your blood sugar start to rise dramatically and you are diagnosed with diabetes to get your antibodies tested to determine if you are Type 1 or Type 2 as having another autoimmune disorder (thyroid) can be an indicator of Type 1.