Hello – Hopefully, you have followup labs scheduled to see if the issue persists. TSH can be an early warning sign that T3 and T4 are headed out of balance, even if they are still in the “normal” range.
It’s not uncommon to need a tweak in dosing as we age – plus, the reformulation probably made things extra challenging. It would also be worth it to report these findings to the pharmacy in case others are having the same issue.
Did your doctor provide any guidance on the nature-throid? It’s a desiccated product like Armour. He or she might have concerns about starting you on a product with T3 (which is the more powerful and active form of thyroid hormone) with your TSH already suppressed.