How to Tell if you Have a Thyroid Problem?

I’m 19 years old and overweight. I’ve tried dieting i the past, didn’t do much (if anything). My grandmother has a thyroid condition. With her medication she doesn’t gain any weight (in fact, she can eat anything). Neither of my parents have thyroid problems. Is thyroid-ism passed genetically? Does it skip a generation? How can you tell if you have it? Any information about thyroid ism is appreciated. Thanks!