Hyperthyroidism is the most common endocrine disorder in older cats and causes significant welfare impacts if untreated. Effective treatments can restore quality of life when diagnosed promptly.
Feline hyperthyroidism illustrates how a highly treatable condition can cause sustained welfare impact through delayed diagnosis. The signs — weight loss, hyperactivity, increased vocalisations — are often attributed to aging or behavioural changes rather than recognised as endocrine disease. Untreated hyperthyroid cats experience chronic discomfort from elevated metabolic rate, cardiac strain, hypertension, and progressive organ damage. Blood pressure-induced retinal detachment causing sudden blindness is among the more dramatic consequences of untreated disease. Once diagnosed and treated, most cats show rapid improvement: weight stabilises, activity normalises, and cardiac complications resolve if caught before permanent damage occurs. The welfare case for routine senior screening including thyroid assessment from age 10 is strong — the treatment investment is modest and the quality of life improvement profound. Owners who notice unexplained weight loss in an older cat eating well should seek veterinary assessment urgently.