Hypo/hyper- thyroid confusion.?

Patient is a 75-year-old female, average health, inactive.

Tests indicate she has a hyperactive thyroid. Approximately 50 years ago, she had a partial thyroid removal. Reason is unknown other than she had a goiter removed from one side. After this, she conceived (a previous problem) and was normal until about 15 years ago. At this time, she was diagnosed with hypothyroidism and put on Synthroid.

About two years ago, she began experiencing the symptoms of hypothyroidism again. Her tests read "normal," a meaningless term since we are all different. The doctors would never say anything other than normal. As it turns out, her results were borderline HIGH.

She changed doctors repeatedly. Finally, she managed to talk one of them into sending her to a specialist (endocrinology). However, she increased her dosage AMA and all of her symptoms went into remission. When she saw the endocrinologist, she was diagnosed as having hyperthyroidism. They began reducing her doses of Synthroid.

Instead of getting better, she has shown signs of getting worse, with an increase in all of her symptoms, first returning to her previous condition and then getting worse.

As I understand it, some of the symptoms of hyper and hypothyroidism as similar, if not the same. My concerns are about the depression, anxiety, irritability, intolerance to cold, and so forth.

It is impossible to be both hyper and hypo at the same time. The tests read one way and the symptoms read the other. So, my question is…

Is there any other condition that could cause symptom of one and the test results of the other?

Her only medication is Synthroid. She was previously diagnosed with depression but no medicines treated it. When she increased the Synthroid, double the dosage, everything went into remission. Something no other medicine has been able to do.