The choice between radioactive iodine therapy and daily oral medication for feline hyperthyroidism involves welfare trade-offs around treatment stress, long-term compliance burden, and risk of concurrent kidney disease.
The hyperthyroidism treatment decision has genuine welfare dimensions beyond clinical efficacy. I-131 achieves cure with a single treatment but requires 1-2 weeks of facility isolation - a period of significant stress for cats separated from their owners and home environment. Methimazole avoids the isolation stress but requires twice-daily restraint for medication administration across the cat's remaining lifespan, which for some cats is a significant daily welfare cost. The risk of unmasking CKD after treatment - present with any effective therapy - makes pre-treatment renal assessment essential. Welfare-centered decision-making matches the treatment approach to the individual cat's temperament, the owner's capacity, and the cat's concurrent health status.