Hello and welcome – as you noted, patients do often need tweaks in dosage as they age. Another thought is that hyperthyroidism can recur if the thyroid isn’t fully destroyed by RAI. These days, doctors give a “fully ablative dose” – but in decades past, some doctors thought they could give a “Goldilocks” dose to correct the hyperthyroidism without needing thyroid hormone replacement.
As far as I know, the thyroid, the cells and tissues behind the eyes, and the skin (often on the front of the shin) are the primary targets for Graves’ antibodies. But certainly other organs can be affected when thyroid levels are out of balance – and perhaps future research will shed more light on whether antibodies are directly involved.