What Is The Cause And Treatment For Thyroid Dysfunction?

I recently had a full blood test, everything was excellent except my thyroid. I was told it is 'out of whack' and I have an overactive thyroid. I have not lost any weight (may have put on a bit) I am not nervy, no dry skin, the only problems I've had are palpitations. (The reason I asked for a full check up). I am 70 years old and do not take any medication. I am reluctant to begin thyroid medication and would appreciate your advice on any way I can control this condition. I gave up alcohol 3 weeks ago and improving my diet, any other advice would be welcome. Thank you. Jean Bowles.