I've got an underactive thyroid = my immune system is good at fighting off most things very well. However, I have had a mild cough for about a week - no temperature or other symptoms, so I had dismissed it as just a small cough. I did have a few days with an awful headache though. I have just been sent home from work in a school though as they are concerned that it could be CV - but very mildly due to my immune system.....I'm still not sure that it is though and not just a bit of a cough. Has anyone else got an underactive thyroid and had mild symptoms similar to mine? If I have got it with just very mild symptoms, I feel very guilty for going into work for the past week unaware :(