High TPO or TG usually means that you have Hashimoto's
You also want to make sure that you doctor orders FT3 and FT4 (not T3 or T4)
If your thyroxine doesn't seem to help you may want to ask your doctor to also check you reverse-T3 levels
When you were originally diagnosed and started on thyroid med, what was your TSH level and also Free T4 if tested? Also reference ranges for those, if you have them.
If you had Hashi's then, further testing now isn't really needed for further treatment. Taking only 75 mcg of T4 med is most likely to have been inadequate for you. Even if it got your Free T4 to an adequate level, it is most unlikely that your Free T3 is adequate. So, as Jenn said, those should be number one priority for tests. I expect that your ongoing hypo symptoms are due to inadequate med needed to get your Free T4 to about mid-range, and your Free T3 into the upper half of its range, adjusted as needed to relieve hypo symptoms. I doubt that RT3 is an issue at this time, but if you can get the doctor to test, do so.
I think that in one of the many threads you have started, I mentioned the importance of Vitamin D, B12 and ferritin, so get those tested. Also, hypothyroid patients , especially women, often have cortisol issues as well, so ask to get that tested.
It is best to not take your med the morning of the blood draw for thyroid tests, in order to avoid false high results. This is even recommended in the ATA/AACE Guidelines for Hypothyroidism.
For continuity, in the future please add further questions to this or one of your other threads and don't start a new one. We don;t want to overlook anything important, and multiple threads from the same member makes it hard to track everything. :)
Your thyroid gland produces mostly T4 and some T3. For use by the body T4 has to be converted to the biologically active form T3. Most of the T3 in your body comes from conversion of T4 in tissue throughout the body. Some T4 is also converted to Reverse T3. The ratio of the two depends on a number of variables.
From the paper "Diagnosis and Treatment of Hypothyroidism: A Patient's Perspective", "Hypothyroidism can occur due to excess conversion of T4 to Reverse T3 (RT3), a biologically inactive „mirror image version of T3. Thus, "RT3 is an excellent marker for reduced cellular T4 and T3 levels not detected by TSH or serum T4 and T3 levels” 35. There is also evidence of RT3 binding to membrane receptors 36, 37 and producing hypo-metabolic effects. "38
Excess RT3 is seldom a problem; however, it is a good idea to test at least initially, to make sure, Or if the doctor refuses to test, it can be deferred and evaluated later if nothing else shows as a problem and you still have hypo symptoms.