Investigation of the effects of hyperthyroidism on renal function in the cat.

This study evaluated the effects of thyroxine on renal function in the cat. Baseline serum thyroxine (T4) concentrations, clinicopathologic data (complete blood count [CBC], serum chemistry panel, urinalysis), and nuclear medicine determinations of glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and effective renal blood flow (ERBF) were measured in 10 normal adult cats. Cats were then injected with thyroxine (T4) (50 micrograms/kg SQ) daily for 30 d to induce hyperthyroidism. Clinicopathologic and nuclear medicine studies were repeated at 30 d. Cats injected with thyroxine had significant increases in T4, GFR, and ERBF and significant declines in serum creatinine and blood urea nitrogen (BUN) values. Administration of high doses of exogenous thyroxine to cats results in significant stimulation of renal function.