It may be worth coming off the PTU to see what really happens, also of interest would be TSI
and TBII which are markers for
Graves disease. If you are on a low dose
PTU (50-100mg/day total), stopping it may reasonable with close observation. Remeber, I-131 therapy is never an emergency, so it is important to make certain the hyperthyroidism is likely a consistent problem requiring definitive treatment;.