Radioiodine (I-131) treatment offers a single-treatment cure for feline hyperthyroidism with minimal welfare burden, making it the gold standard treatment for cats with access to specialist centers.
The welfare comparison between radioiodine and daily oral medication for feline hyperthyroidism is instructive: radioiodine requires a single injection and a temporary isolation period, while oral medication requires twice-daily pilling for the rest of the cat's life - a procedure that many cats find highly aversive and that owners often fail to maintain consistently. The isolation period post-radioiodine is a welfare cost, but it is time-limited and the cat is otherwise healthy. The chronic welfare cost of twice-daily pilling, potential adverse drug effects, and inconsistent control of thyroid levels with oral medication can be substantial over years. For cats without access to radioiodine facilities, oral medication remains important - but for those with access, radioiodine typically represents the superior welfare outcome.