No, cancer would not cause it, probably more like aging
/hormonal changes. The only test for cancer post-thyroidectomy is
a thyrogen test, they inject you with thyrogen then test for a spike in your thyroglobulin. How old are you? Could you have low hormones due to aging? Sometimes they have to adjust your meds due to normal aging changes. If you are concerned about cancer, you can ask for a thyrogen test.