In the untreated state, there is a continuous low flow of thyroid hormone that creates an equilibrium among the hypothalamus/pituitary/thyroid gland. When taking a daily replacement amount of thyroid med all at once, that has a suppressive effect on the TSH output, since there is no need for TSH stimulation of the thyroid gland. Although frequently interpreted as hyperthyroidism, such a suppressed TSH does not mean hyperthyroidism unless there are hyper symptoms due to excessive levels of Free T4 and Free T3. There are a number of members, including myself, that have had suppressed TSH for many years without ever having hyper symptoms. Accordingly TSH should not be relied on to determine the medication dosage. Dosage should be adjusted as needed to relieve hypo symptoms, not based on lab test results.
Since all of your Free T4 and Free T3 is the result of the thyroid medication, I would not suggest reducing the T4 dosage to 25. Mid-range is a good target for Free T4, so reducing the level from 1.7 to 1.3 would require approx. a 25% reduction in T4 med, so it seems that a dosage of 50-62.5 would be more appropriate. Along with that, keeping the same T3 dosage would likely reduce your Free T3, due to less available for conversion, when you rally want to increase your T3 dosage, and raise your Free T3 level, and increase your Free T3 to RT3 ratio. After these changes if your RT3 remains high, then a further decrease in T4 med might be required.
So I think that you are going to have to convince your doctor that the suppressed TSH is not a concern, in order to get where you need to be. I think you could make good use of the link I think I gave you previously.
In the paper, in Rec. 10 on page 13, there is more than adequate scientific evidence that TSH suppression is not a cause for concern. Also, note Ref. 36, which concluded from a study that “Measurements of serum concentrations of total thyroxine, analogue free thyroxine, total triiodothyronine, analogue free triiodothyronine, and thyroidstimulating hormone, made with a sensitive immunoradiometric assay, did not, except in patients with gross abnormalities, distinguish euthyroid patients from those who were receiving inadequate or excessive replacement. These measurements are therefore of little, if any, value in monitoring patients receiving thyroxine replacement.”
Your ferritin level was also much too low so you need to supplement with a good form of iron to optimize to at least 100. I have found Vitron C to be a good iron supplement since it contains 65 mg of iron and also Vitamin C to help prevent possible stomach distress from the iron. Other good forms are ferrous fumarate, ferrous bisglycinate, and ferrous sulfate.
Were you tested for Vitamin D and B12?
If you drop your T4 med to 25 mcg and do not increase your T3 med significantly you are going to regress.
I think I would mention to the doctor that a suppressed TSH is of concern only in an untreated thyroid patient, because in that situation it is a signal of excessive levels of FT4 and FT3. With a thyroid patient taking full daily replacement doses of thyroid med, what does a suppressed (or almost nonexistent) TSH supposedly indicate? TSH cannot be shown to correlate well with either FT4 or FT3, and certainly your FT4 and FT3 are not excessive, even with the suppressed TSH. So, what function would be adversely affected by a lack of TSH? The doctor won't have an answer for that, only her misgivings, based on not understanding what daily replacement doses of thyroid med do to the TSH level.
Following is another source of info on suppressed TSH.