If you experience Anxiety & Panic Attacks it may very well be a "secondary" condition to another physical illness.
Of course, the only way to know for sure is to be as open and honest with your doctor about your symptoms and your lifestyle as possible (even if it is embarrassing).
There are so many things that can contribute or have caused your anxiety disorder and panic attacks that the list is just incredibly long.
Here are just a few possible physical causes of anxiety disorder and panic attacks:
Low potassium levels
High potassium levels
Medications (including the one's that are prescribed for anxiety & panic)
Work place stress
Witnessing or being a part of a traumatic event
If your anxiety & panic attacks have become a disorder then you're not only going to have to treat the primary cause (which could be anything from the list above and more), but also treat the anxiety & panic disorder as you have developed a new response to fear and stress.
Note: Never self diagnose. Make sure you visit your local GP first. All material provided is for informational or educational purposes only. No content is intended to be a substitute for professional medical advice, diagnosis or treatment. Consult your doctor regarding the applicability of any opinions or recommendations with respect to your symptoms or medical condition.