Are you only on Nature Throid? The T3/T4 ratio in pig thyroid does not match the ratio within humans since a normal, healthy thyroid produces somewhere in the range of 10:1 T4 to T3. It appears that over the long run, your T4 became depleted which is why your symptoms have returned. I would suggest you add more T4 to your regimen and see how you respond.
Another thing to note is that a lot of the thyroid dosage recommendations out there are targeted towards women since 90% of hypothyroid cases are female. Unfortunately as males, too much T3 can drive up our SHBG and inhibit our testosterone so that's something to be aware of. I would argue that males tend to do better on LESS T3 than women. My own experience fits this theory. I was on WP Thyroid 2 grains for 2 years, even adjusting to 3 grains since it was hammered in my head that fT3 should be within a certain range. I only started making real progress after dropping my WP Thyroid to 0.5 grains and upping my T4 to 100 mcg.
Lastly, T3 and T4 levels don't tell you everything. For example, T4->T3 conversion can happen intracellularly and that's something we can't test for yet (look up Type 2 deiodinase). Good luck!
