Comparison of the Changes in Quality-of-Life of Cats with Hyperthyroidism Treated with Radioiodine or Antithyroid Drugs—A Preliminary Study

A previous cross-sectional study found impaired health-related quality of life (HRQoL) in hyperthyroid cats, but the longitudinal impact of treatment-especially differences between radioiodine (RAIT) and antithyroid drug (ATD) approaches-remains unclear. This study aimed to evaluate changes in HRQoL in recently diagnosed (<6 months) hyperthyroid cats that underwent RAIT or received ATD. HRQoL was assessed using the validated HyperthyroidismQoL-cat questionnaire at baseline and after 1, 3, and 6 months, alongside thyroid status (eu-/hypo-/hyperthyroid) evaluation. Mixed-effects model analysed the influence of treatment type, timepoint, and thyroid status on log(HRQoL). HRQoL differences between groups at baseline and comparison to a non-hyperthyroid control group (n = 322) from a previous study at month 6 were examined using Mann-Whitney U tests. Data are presented as median (range), with significance set at <i>p</i> < 0.05. Thirty-eight client-owned hyperthyroid cats (15 ATD, 23 RAIT) were included. HRQoL scores at baseline did not differ between groups (RAIT: 103.5 [27-211], ATD: 73 [22-260], <i>p</i> = 0.22). HRQoL significantly improved over time (<i>p</i> < 0.001) but was not affected by treatment type (<i>p</i> = 0.20) or thyroid status (<i>p</i> = 0.40). Despite improvement, HRQoL remained lower than in non-hyperthyroid controls (hyperthyroid: 42.5 [3-161.5], non-hyperthyroid: 27 [0-249], <i>p</i> = 0.007). This study highlights the overall positive impact of treatment on HRQoL, but due to the lack of randomisation and heterogeneity of subjects and treatment, conclusion have to be considered preliminary.