Leptin and ghrelin concentration in hyperthyroid cats before and after radioactive iodine therapy compared to euthyroid control cats

Objective: Leptin and ghrelin, two peptide hormones with antagonistic effects on satiety and energy balance, could be involved in the pathogenesis of weight loss and polyphagia in cats with hyperthyroidism. Leptin generally decreases appetite and increases energy expenditure, while ghrelin exerts the opposite effects. Materials and methods: Leptin and ghrelin were measured in 42 client owned hyperthyroid cats with a body condition score (BCS) ≤ 5/9 before (T0) and 4 weeks after radioactive iodine treatment (RAIT) (T1). Dependent on the serum total thyroxine concentration concentration at T1, cats were sub-classified as still hyperthyroid (ht-ht) (n = 4), euthyroid (ht-eu) (n = 10) or hypothyroid (ht-hypo) (n = 28). Results were compared to those of 22 healthy, euthyroid control cats with a comparable BCS (≤ 5/9) and age (≥ 8 years) to hyperthyroid cats. Results: At T0, there were no significant differences between hyperthyroid and control cats for leptin (p = 0.06) or ghrelin concentrations (p = 0.27). At T1, leptin significantly decreased in ht-hypo cats compared to T0 (p = 0.0008) despite a significantly increased body weight in this group (p = 0.0001). Serum ghrelin concentrations did not differ between hyperthyroid cats with a history of polyphagia compared to non-polyphagic cats (p = 0.42). After RAIT, ghrelin concentration significantly increased in all hyperthyroid cats (p