[ Diet & Fitness ] Open Question : why was I diagnosed with Hypothyroidism if I have a fast metabolism and I'm always skinny?

[ Diet & Fitness ] Open Question : why was I diagnosed with Hypothyroidism
if I have a fast metabolism and I'm always skinny?

I thought people with an under active thyroid were suppose to have a slow
metabolism and be overweight? I'm not and I have a really fast metabolism
so is it possible that my doctor is wrong? And also is it possible to have
a high metabolism and be really skinny if you have hypothyroidism? Thanks
if you can answer my questions