Can you develop hyperthyroidism?

I am consistently tired, and have severe anxiety and depression. I cannot remember if I had the bloodtest for hyperthyroidism a couple of years ago (when I was tested for anemia and glandular fever, tested positive for glandular fever). If I was tested which I cannot remember, it must've come back negative otherwise I would remember...but, my CBT therapist asked me about whether I had been tested as it may be a possibility. 

Is it possible for if I was tested negative, for me to now have developed hyperthyroidism?? Please help! Thanks 

Yes, you can develop it at any time. I have had my thyroid tested several times during my life and it was normal. Then in March this year I was found to have quite severe hyperthyroidism. I am 53.

Your values can be in the normal range, but they may not be normal for your body. That's why so many people go years with a thyroid problem undiagnosed. I started to have symptoms of hyper at 23 years of age, after the birth of my second child. I had every symptom of hyper, anxiety was my worst one. All doctors ignored me because they all thought I was hypochondriac. 3 years ago, at the age of 40, I was diagnosed with Graves' disease and I am now awaiting a total thyroidectomy. The anxiety is fierce and is still to this day the worst symptom I have.

Hi Aimee....go get tested again....it is a possibility

Make sure they test all three thyroid tests, i.e. TSH, Free T3, Free T4.  It is possible especially at the beginning of a thyroid illness to have an abnormality of Free T3 or T4 but normal TSH initially.  That's what happened to me.