An investigation of predictors of renal insufficiency following treatment of hyperthyroidism in cats

Abstract

To determine if routine pre-treatment clinical data can be used to predict the development of overt renal insufficiency following treatment of feline hyperthyroidism, we studied retrospectively all non-azotemic cats undergoing treatment for hyperthyroidism at our hospital. Medical records were reviewed for signalment, clinical signs, and serum biochemical, hematologic and urinalysis parameters before and after treatment for hyperthyroidism. Two groups - cats that developed post-treatment renal insufficiency, and those that did not - were compared. No significant differences could be detected between the groups with respect to the parameters measured. Our study suggests that the results of routine pre-treatment clinical data cannot be used to reliably predict renal function after treatment for hyperthyroidism, validating the necessity of a methimazole trial prior to definitive therapy. The widely held belief that cats with pre-treatment urine specific gravity>1.035 are at less risk for development of renal azotemia after treatment of hyperthyroidism seems unwarranted.

American Association of Feline Practitioners: Senior Care Guidelines

“…Note that: -Hypertension may persist or even develop after treatment. 21,64,65 -Hypertension secondary to hyperthyroidism alone may self-correct when a euthyroid state is achieved. 18 -Renal function should be monitored.…”

PTH and ionized calcium evaluation in unilateral thyroidectomized cats

“…Successful treatment of hyperthyroidism decreases renal excretory function, resulting in an increase in the serum creatinine concentration and a decrease in the glomerular filtration rate. (Bichard, 2006, Riensche et al, 2008Williams et al 2010). 26,4% (Williams et al, 2010 to 51% (Riensche et al, 2008) of hyperthyroid cats developed renal insufficiency within 2 weeks to 6 months after hyperthyroidism treatment.…”

“…(Bichard, 2006, Riensche et al, 2008Williams et al 2010). 26,4% (Williams et al, 2010 to 51% (Riensche et al, 2008) of hyperthyroid cats developed renal insufficiency within 2 weeks to 6 months after hyperthyroidism treatment. Renal functional must be monitored closely in cats after hyperthyroidism treatment.…”

Concurrent Disease Management

“…Therefore in cats with clinical signs compatible with hyperthyroidism, a normal total thyroxine (total T 4 ) treatment with radioiodine, while other reports have found even higher numbers of cats experiencing a crisis after treatment. 16,192,222,234 In general, no significant differences have been seen when comparing the pretreatment parameters in cats that did develop a posttreatment renal azotemia with those that did not. Significant decreases in renal function are generally evident by 4 weeks posttreatment, after which time GFR stabilizes with very little deterioration, depending on the degree or stage of renal disease.…”