Hi SR. yes, simple blood test and they can tell. I found out about having it about 8 years ago (im 44 now), simple blood test identified it. had a cholersterol test at work and they said it was high and to see your GP. turns out cholesterol was okay but hypothyroidism was the cause. on Thyroxine to replace whats missing. tablet first thing in the morning and thats it, not a big deal.
as for symptoms, unable to lose weight, knackered all the time and bad moods/feeling fed up. didnt have the sensitivity to cold thing but i guess you wont get all the symptoms.
get the test done, if nothing else it will put your mind at rest