I just read earlier on the thyroid board that a bad case of mono can trigger a thyroid problem. However, you may have had the enlarged thyroid long before you had mono. If I had to guess, I would say that you probably had the thyroid problem first.
I would recommend having some bloodwork done to test your thyroid levels. The first test is called TSH, which I believe is included in any complete blood count (CBC). That will help signal if your thyroid is out of whack. Other tests include Free T3, Free T4, and others. I would also recommend having a thyroid ultrasound which will help determine the size of your thyroid gland. It will also show any thyroid nodules you may have. Further testing can be done to determine the nature of any nodules. For now, just get the blood testing done.
