Questioning the Need for Thyroid Medication

Hi! I'm new to the app and thought this might be a good way to work on making myself better and understand my conditions. Recently I had to go to the doctor because I have an autoimmune disease and keep getting upper respiratory infections. In May, I had Strep. Now doctors are thinking I may now have asthma which isn't fun. While seeing my doctor, she asked me if I still took my thyroid medication and I told her I do not. I haven't taken it in years but I truly don't think I need it. Last I had my levels checked, they were normal and I wasn't on the medication on that time, as I had just decided to stop taking it. The doctor brought up to me how dangerous it could be for me to not be taking it. Would it really affect anything? I never felt like it did anything.