Research Communications of the 27(th) ECVIM-CA Congress: Intercontinental, Saint Julian's, Malta, 14th to 16th September 2017

Disclosures: No disclosures to report. Iatrogenic hypothyroidism can develop post-radioiodine treatment for feline hyperthyroidism; its incidence may be dose-dependent. Cats that develop iatrogenic hypothyroidism have a greater incidence of development of azotemia than cats that remain euthyroid. Dogs with experimentally-induced hypothyroidism have both decreased glomerular filtration rate (GFR) and endogenous creatinine production. This suggests that using creatinine as a marker of kidney function in hypothyroid cats could underestimate the incidence of development of kidney disease. This longitudinal study evaluated thyroid and renal function in cats post low-dose (111 MBq) radioiodine therapy. Hyperthyroid cats presented for low-dose radioiodine therapy to The Feline Centre, Langford Vets were prospectively enrolled into the study. At baseline, one, six and 12-months post-radioiodine treatment, thyroid and renal function were evaluated via total thyroxine (TT4) and thyroid stimulating hormone (TSH), and via serum creatinine concentration (SCr) and GFR (corrected slope-intercept iohexol clearance), respectively. Cats were categorized as overt hypothyroid (TT4 < 15 nmol/L, TSH>0.15 ng/mL), subclinical hypothyroid (TT4≥15-60 nmol/L, TSH>0.15 ng/mL), euthyroid (TT4≤60 nmol/L, TSH≤0.15 ng/mL) and hyperthyroid (TT4>60 nmol/L) at each timepoint. Decreased GFR was defined as <0.92 mL/min/kg and azotemia as SCr>175 µmol/L.