Association of Iatrogenic Hypothyroidism with Azotemia and Reduced Survival Time in Cats Treated for Hyperthyroidism

Background: Iatrogenic hypothyroidism can occur after treatment of hyperthyroidism, and is correlated with a reduced glomerular filtration rate in humans and dogs. Hypothesis: Cats with iatrogenic hypothyroidism after treatment for hyperthyroidism will have a greater incidence of azotemia than euthyroid cats. Animals: Eighty client owned cats with hyperthyroidism. Methods: Two retrospective studies. (1) Longitudinal study of 12 hyperthyroid cats treated with radioiodine (documented as euthyroid after treatment), to assess changes in plasma thyroid stimulating hormone (TSH) concentration over a 6‐month follow‐up period, (2) Cross‐sectional study of 75 hyperthyroid cats (documented as euthyroid) 6 months after commencement of treatment for hyperthyroidism to identify the relationship between thyroid status and the development of azotemia. Kaplan‐Meier survival analysis was performed to identify relationships between thyroid and renal status and survival. Results: Plasma TSH concentrations were not suppressed in 7 of 8 cats with hypothyroidism 3 months after radioiodine treatment. The proportion of cats with azotemia was significantly (P= .028) greater in the hypothyroid (16 of 28) than the euthyroid group (14 of 47). Twenty‐eight of 41 cats (68%) with plasma TT4 concentration below the laboratory reference range had an increased plasma TSH concentration. Hypothyroid cats that developed azotemia within the follow‐up period had significantly (P= .018) shorter survival times (median survival time 456 days, range 231–1589 days) than those that remained nonazotemic (median survival time 905 days, range 316–1869 days). Conclusions and Clinical Importance: Iatrogenic hypothyroidism appears to contribute to the development of azotemia after treatment of hyperthyroidism, and reduced survival time in azotemic cats.     

Evaluation of Predictors of the Development of Azotemia in Cats

Background: Chronic kidney disease (CKD) is a common condition in geriatric cats. Diagnosis is based on the development of persistent azotemia with inadequate urine concentrating ability. Biomarkers are sought for early identification.
Hypothesis: Clinical variables, urine concentrating ability, proteinuria, and N -acetyl-β- d -glucosaminidase (NAG) index will be predictive of cats at risk of developing azotemia within 12 months.
Animals: Client-owned nonazotemic geriatric (≥9 years) cats.
Methods: Prospective longitudinal cohort study monitoring a population of healthy nonazotemic geriatric cats every 6 months until development of azotemia, death, or the study end point (September 30, 2007). Multivariable logistic regression analysis was used to assess baseline clinical, biochemical, and urinalysis variables, urine protein to creatinine ratio (UP/C), urine albumin to creatinine (UA/C) ratio, and urinary NAG index as predictors of development of azotemia.
Results: One hundred and eighteen cats were recruited with a median age of 13 years. Ninety-five cats (80.5%) had been followed or reached the study end point by 12 months of which 30.5% (29/95) developed azotemia. Age, systolic blood pressure, plasma creatinine concentration, urine specific gravity, UP/C, UA/C, and NAG index were significantly associated with development of azotemia in the univariable analysis ( P ≤ .05). However, in the multivariable analysis, only plasma creatinine concentration with either UP/C (Model 1) or UA/C (Model 2) remained significant.
Conclusions and Clinical Importance: This study demonstrates a high incidence of azotemia in a population of previously healthy geriatric cats. Proteinuria at presentation was significantly associated with development of azotemia although causal association cannot be inferred. Evaluation of NAG index offered no additional benefit.     

Survival in cats with naturally occurring chronic kidney disease (2000-2002)

Background: Duration of survival of cats with naturally occurring chronic kidney disease (CKD) is poorly characterized.
Hypothesis: Stage of kidney disease based on serum creatinine concentration (SCr) at the time of diagnosis and after correction of prerenal azotemia is strongly associated with duration of survival in cats.
Animals: Two hundred and eleven client-owned cats with naturally occurring CKD evaluated between April 2000 and January 2002.
Methods: Retrospective case review of 733 cats with SCr > 2.3 mg/dL. Examination of the medical records identified 211 cats that met all other inclusion and exclusion criteria for this study. Clinical characteristics, clinicopathologic data, and survival times were extracted from the medical record. Owners and referring veterinarians were contacted by phone to obtain follow-up if it was not documented in the record. Kaplan-Meier survival curves were performed to determine survival times for International Renal Interest Society (IRIS) stage both at diagnosis and at baseline (ie, after correction of prerenal azotemia).
Results: Median survival for cats in IRIS stage IIb at the time of diagnosis was 1,151 days (range 2–3,107), and was longer than survival in stage III (median 778, range 22–2,100) or stage IV (median 103, range 1–1,920) ( P -value < .0001). P -value for effect of stage at diagnosis was <.0001.
Conclusions and Clinical Importance: IRIS stage of CKD based on serum creatinine at the time of diagnosis is strongly predictive of survival in cats with naturally occurring CKD.     

Measurement, interpretation, and implications of proteinuria and albuminuria.

Proteinuria is a common disorder in dogs and cats that can indicate the presence of chronic kidney disease (CKD) before the onset of azotemia or the presence of more severe CKD after the onset of azotemia. Although a direct pathogenetic link between glomerular disease, proteinuria, and progressive renal damage has not been established, attenuation of proteinuria has been associated with decreased renal functional decline in several studies. There is a need to continue to increase our understanding of the effects of proteinuria on the glomerulus, the tubule, and the interstitium in dogs and cats.     

Effect of control of systolic blood pressure on survival in cats with systemic hypertension

BACKGROUND: Systemic hypertension is a common clinical problem, often occurring in association with renal disease in cats. Limited information is available to assess the effect of blood pressure and the treatment of hypertension on survival. HYPOTHESIS: That adequacy of blood pressure control is associated with the duration of survival in cats with systolic hypertension. ANIMALS: One hundred and forty-one client-owned cats with systolic hypertension. METHODS: Hypertensive cats were treated with amlodipine besylate and were followed until death or the study end point. Time-averaged systolic blood pressure (SBPOT) after implementation of antihypertensive medication and stabilization of systolic blood pressure (SBP) was calculated by using the equation (area under the curve/survival [days]). Cats were divided into quartiles based on their SBPOT, representing varying levels of blood pressure control (median [25th, 75th percentile]: Q1 = 137 [132, 141] mm Hg, Q2 = 148 [145, 151] mm Hg, Q3 = 157 [155, 158] mm Hg, Q4 = 170 [164, 175] mm Hg). Survival and clinical variables were compared between the quartiles. Cox proportional hazard regression analysis was used to determine the association of age, renal function, proteinuria, SBPOT, and the presence of hyperthyroidism on survival. Urine protein to creatinine ratio (UP:C) was compared at diagnosis of hypertension and after initiating treatment. RESULTS: Only UP:C and SBP at diagnosis differed significantly between SBPOT quartiles. Proteinuria was the only variable significantly related to survival in hypertensive cats. A significant decline in UP:C was found in cats treated with amlodipine besylate. CONCLUSIONS AND CLINICAL IMPORTANCE: Proteinuria before and after treatment of hypertension is strongly associated with survival in cats with systolic hypertension. Treatment with amlodipine besylate can result in a significant reduction in UP: C.     

N-acetyl-beta-D-glucosaminidase index as an early biomarker for chronic kidney disease in cats with hyperthyroidism

Background: Hyperthyroid cats are at risk of developing azotemic chronic kidney disease (CKD) and diagnostic tools currently used to screen for CKD in hyperthyroid cats are either unreliable or impractical.
Hypothesis: Urine N -acetyl-β- d -glucosaminidase index (NAG_i) is a good biomarker for azotemic CKD in hyperthyroid cats.
Animals: Twenty-four newly diagnosed nonazotemic hyperthyroid cats and 10 healthy cats.
Methods: All cats were evaluated for hyperthyroidism at baseline. Hyperthyroid cats were treated with methimazole and reevaluated once euthyroid. At the end of the study, cats were divided into 3 groups: healthy cats, nonazotemic, and azotemic euthyroid cats. Baseline group characteristics were compared to predict azotemic CKD. The influence of treatment on NAG_i was evaluated.
Results: Baseline NAG_i was significantly different among groups ( P = .004). Azotemic cats had a higher median value (13.12 U/g) when compared with healthy cats (1.38 U/g). With NAG_i >2.76 U/g, negative and positive predictive values for development of azotemia were 77.7 and 50%, whereas the combination of a urine specific gravity (USG) ≤1.035 and T₄ >7.80 μg/dL enhanced predictive values to 88.9 and 83.3%, respectively. NAG_i values decreased significantly over time in treated nonazotemic cats.
Conclusions and Clinical Relevance: Baseline NAG_i did not differentiate azotemic from nonazotemic euthyroid cats. NAG_i could be used to assess renal function during medical therapy allowing the clinician to adjust methimazole dosage accordingly. The combination of USG and T₄ could optimize identification of appropriate candidates for permanent treatment of hyperthyroidism.     

Association between urinary vascular endothelial growth factor excretion and chronic kidney disease in hyperthyroid cats

Many hyperthyroid cats develop azotaemic chronic kidney disease (aCKD) following treatment, which has led to the hypothesis that hyperthyroidism might be detrimental to renal function. Renin-angiotensin-aldosterone system (RAAS) activation occurs in hyperthyroidism, which could cause peri-tubular hypoxia, tubular damage and the development of aCKD. Urinary vascular endothelial growth factor:creatinine ratio (VEGFCR) is postulated to be a marker of tubular hypoxia. VEGFCR was correlated with plasma renin activity (PRA) and compared between hyperthyroid cats that did and did not develop aCKD following treatment (pre-azotaemic and non-azotaemic groups respectively). PRA was positively correlated with VEGFCR (r_s = 0.382; P = 0.028); however, pre-azotaemic hyperthyroid cats had significantly lower VEGFCR than non-azotaemic cats at baseline (median 122.3 fg/g versus 167.0 fg/g; P < 0.001). RAAS activation in hyperthyroidism is associated with increased VEGFCR; however, increased VEGFCR was not correlated with the development of aCKD. Therefore, tubular hypoxia may not be a mechanism for renal damage in hyperthyroid cats.     

Survival of cats with naturally occurring chronic renal failure is related to severity of proteinuria

BACKGROUND: Tubulointerstitial kidney disease is a common cause of illness and death in pet cats and is typically not associated with overt proteinuria. HYPOTHESIS: Proteinuria would be independently related to survival in cats with renal failure, with or without hypertension. ANIMALS: The study included 136 client-owned cats; 28 apparently normal, 14 hypertensive but not azotemic, 66 azotemic but not hypertensive, and 28 both hypertensive and azotemic. METHODS: Cox's proportional hazards model was used to determine the influence of initial plasma creatinine concentration, proteinuria (urine protein-to-creatinine ratio or albumin-to-creatinine ratio), age, and systemic hypertension on the risk of death or euthanasia during the follow-up period. Multivariable linear regression was used to determine the relation between severity of proteinuria and predictive variables, including age, plasma creatinine concentration, systolic blood pressure, sex, and urine specific gravity. RESULTS: Plasma creatinine concentration and proteinuria were very highly related to survival. The hazard ratio (95% confidence intervals) for death or euthanasia was 2.9 (1.4-6.3) and 4.0 (2.0-8.0) for urine protein-to-creatinine ratio 0.2-0.4 and >0.4, respectively, compared with the baseline group with a urine protein-to-creatinine ratio of <0.2 and were 2.4 (1.2-4.8) and 4.9 (2.3-10.2) for an albumin-to-creatinine ratio of 30-82 mg/g and <82 mg/g, respectively, compared with a baseline group with albumin-to-creatinine ratio of <30 mg/g. Treated hypertensive cats did not have reduced survival, although systolic blood pressure, together with plasma creatinine concentration was positively related to the magnitude of proteinuria. CONCLUSIONS AND CLINICAL IMPORTANCE: Despite the relatively low concentrations of proteinuria typical of chronic renal disease in cats, this measurement is of prognostic significance.     

Prognostic factors in cats with chronic kidney disease

BACKGROUND: Chronic kidney disease (CKD) is a common cause of morbidity and mortality in cats. HYPOTHESIS: Some baseline variables are associated with shorter survival times in cats with CKD. ANIMALS: Client-owned cats. METHODS: Cats with CKD with initial plasma creatinine concentration > or =2.0 mg/dL and urine specific gravity (USG) < or = 1.025 were recruited into a prospective clinical trial that compared benazepril with a placebo. We describe baseline variables in 190 cats and their influence on renal survival time in the placebo group (95 cats), which was followed for up to 1,097 days. Renal survival time was defined as the time from initiation of therapy to the need for parenteral fluid therapy, euthanasia, or death related to renal failure. RESULTS: Of the 95 cats treated with a placebo, 58 were censored and 37 reached the renal survival end point (died, n = 0; euthanized, n = 17; parenteral fluids, n = 12; parenteral fluids followed by euthanasia, n = 8). Increased plasma creatinine concentration, increased urine protein-to-creatinine ratio (UPC), and increased blood leukocyte count were significantly (P < .01) associated with a shorter renal survival time and were independent risk factors. Increased concentrations of plasma phosphate or urea, and lower blood hemoglobin concentration or hematocrit were significantly (P < .01) associated with a shorter renal survival time and were dependent risk factors, because they also were significantly (P < .01) correlated with plasma creatinine concentration at baseline. CLINICAL IMPORTANCE: Several variables were significantly associated with a shorter renal survival time in cats with CKD.     

Feline thyroid surgery.

Hyperthyroidism is the most commonly diagnosed endocrine disease in cats. Surgery is a widely available curative therapy for hyperthyroid cats. Because of the multiple metabolic changes associated with hyperthyroidism, surgical management can be challenging. Multiple methods of thyroidectomy and their associated levels of morbidity are reviewed.     

Proteinuria: measurement and interpretation

Proteinuria is a general term that describes the presence of any type of protein in the urine (e.g., albumin, globulins, mucoproteins, and Bence-Jones proteins); however, albumin is the predominate protein in urine in healthy dogs and cats as well as dogs and cats with renal disease. Proteinuria can arise from several different physiologic and pathologic causes, but persistent proteinuria associated with normal urine sediment is consistent with kidney disease. The urine dipstick colorimetric test is the usual first-line screening test for the detection of proteinuria, but false-positive reactions are common. When proteinuria of renal origin is suspected, the next diagnostic steps are quantitation and longitudinal monitoring via the urine protein/creatinine ratio. The recent availability of a species-specific albumin enzyme-linked immunosorbent assay technology that enables detection of low concentrations of canine and feline albuminuria has both increased diagnostic capability and stimulated discussion about what level of proteinuria/albuminuria is normal. Beyond being an important diagnostic marker, proteinuria is associated with kidney disease progression in both dogs and cats: the greater the magnitude of the proteinuria, the greater the risk of renal disease progression and mortality. Treatments that have attenuated proteinuria in dogs and cats have also been associated with slowed kidney disease progression and/or improved survival. For these reasons, screening for renal proteinuria and longitudinal assessment of renal proteinuria has recently received renewed interest.     

Ultrasonographic measurements of adrenal glands in cats with hyperthyroidism

Feline hyperthyroidism is potentially associated with exaggerated responsiveness of the adrenal gland cortex. The adrenal glands of 23 hyperthyroid cats were examined ultrasonographically and compared to the adrenal glands of 30 control cats. Ten hyperthyroid cats had received antithyroid drugs until 2 weeks before sonography, the other 13 were untreated. There was no difference in adrenal gland shape between healthy and hyperthyroid cats: bean-shaped, well-defined, hypoechoic structures surrounded by a hyperechoic halo in 43/60 (71.6%) healthy cats and 34/46 (73.9%) hyperthyroid cats; more ovoid in 13/60 (21.6%) healthy cats and 9/46 (19.6%) hyperthyroid cats while more elongated in 4/60 (6.7%) healthy cats, 3/46 (6.5%) hyperthyroid cats. Hyperechoic foci were present in 9/23 (39.1%) hyperthyroid cats and 2/30 (6.7%) healthy cats. The adrenal glands were significantly larger in hyperthyroid cats, although there was overlap in size range. The mean difference between hyperthyroid cats and healthy cats was 1.6 and 1.7 mm in left and right adrenal gland length, 0.8 and 0.9 mm in left and right cranial adrenal gland height, and 0.4 and 0.9 mm in left and right caudal adrenal gland height. There was no significant difference between the adrenal gland measurements in treated and untreated hyperthyroid cats. The adrenomegaly was most likely associated with the hypersecretion of the adrenal cortex documented in hyperthyroid cats. Hyperthyroidism should be an alternative to hyperadrenocorticism, hyperaldosteronism, and acromegaly in cats with bilateral moderate adrenomegaly.     

Acute intrinsic renal failure in cats: 32 cases (1997-2004)

OBJECTIVE: To determine patient demographics, clinicopathologic findings, and outcome associated with naturally acquired acute intrinsic renal failure (ARF) in cats. DESIGN: Retrospective case series. ANIMALS: 32 cats with ARF. PROCEDURES: Cats were considered to have ARF if they had acute onset of clinical signs (< 7 days), serum creatinine concentration > 2.5 mg/dL (reference range, 0.8 to 2.3 mg/dL) and BUN > 35 mg/dL (reference range, 15 to 34 mg/dL) in conjunction with urine specific gravity < 1.025 or with anuria or increasing serum creatinine concentration despite fluid therapy and normal hydration status, and no signs of chronic renal disease. Cases were excluded if cats had renal calculi or renal neoplasia. RESULTS: Causes of ARF included nephrotoxins (n = 18 cats), ischemia (4), and other causes (10). Eighteen cats were oliguric. For each unit (mEq/L) increase in initial potassium concentration, there was a 57% decrease in chance of survival. Low serum albumin or bicarbonate concentration at initial diagnosis was a negative prognostic indicator for survival. Initial concentrations of BUN, serum creatinine, and other variables were not prognostic. Seventeen (53%) cats survived, of which 8 cats had resolution of azotemia and 9 cats were discharged from the hospital with persistent azotemia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that survival rates of cats with ARF were similar to survival rates in dogs and that residual renal damage persisted in approximately half of cats surviving the initial hospitalization.     

Short- and long-term follow-up of glomerular and tubular renal markers of kidney function in hyperthyroid cats after treatment with radioiodine

Hyperthyroidism can mask co-existing chronic kidney disease (CKD). Previous studies showed that post-treatment renal azotemia can be predicted by pre-treatment assessment of glomerular filtration rate (GFR). We hypothesized that treatment of hyperthyroidism may have different effects on glomerular and tubular function and these changes might be predicted by additional pre-treatment variables than GFR.     

Serum fructosamine concentration in cats with overt hyperthyroidism.

OBJECTIVE: To determine the effect of hyperthyroidism on serum fructosamine concentration in cats. DESIGN: Cohort study. ANIMALS: 22 cats with overt hyperthyroidism. PROCEDURE: Hyperthyroidism was diagnosed on the basis of clinical signs, detection of a palpable thyroid gland, and high total serum thyroxine (T4) concentrations. Hyperthyroid cats with abnormal serum albumin, total protein, and glucose concentrations were excluded from the study. Samples for determination of serum fructosamine concentration were obtained prior to initiating treatment. Results were compared with fructosamine concentrations in healthy cats, cats in which diabetes had recently been diagnosed, and cats with hypoproteinemia. In 6 cats, follow-up measurements were obtained 2 and 6 weeks after initiating treatment with carbimazole. RESULTS: Serum fructosamine concentrations ranged from 154 to 267 mumol/L (median, 198 mumol/L) and were significantly lower than values in healthy cats. Eleven (50%) of the hyperthyroid cats had serum fructosamine concentrations less than the reference range. Serum fructosamine concentrations in hyperthyroid, normoproteinemic cats did not differ from values in hypoproteinemic cats. During treatment, an increase in serum fructosamine concentration was detected. CONCLUSIONS AND CLINICAL RELEVANCE: In hyperthyroid cats, concentration of serum fructosamine may be low because of accelerated protein turnover, independent of blood glucose concentration. Serum fructosamine concentrations should not be evaluated in cats with overt hyperthyroidism and diabetes mellitus. Additionally, concentration of serum fructosamine in hyperthyroid cats should not be used to differentiate between diabetes mellitus and transitory stress-related hyperglycemia.     

Results of thyroidectomy in 101 cats with hyperthyroidism

OBJECTIVE: To describe outcome after thyroidectomy in hyperthyroid cats, with emphasis on peri- and postsurgical complications and recurrence. STUDY DESIGN: Retrospective study. ANIMALS: One hundred and one hyperthyroid cats. METHODS: Diagnostic work-up included preoperative measurement of plasma calcium, sodium, potassium, urea, and creatinine concentrations, and thyroid scintigraphy. A modified intracapsular dissection technique was performed. Postoperatively, parathyroid gland function was evaluated by measuring plasma calcium concentration several times daily. Outcome was obtained by standard telephone questionnaire. RESULTS: Thyroid scintigraphy revealed ectopic hyperplastic thyroid tissue (EHTT) in 9 cats. Preoperatively, 29 of 91 cats had hypokalemia. Two cats died within 3 days after surgery and 5 of 86 cats developed postoperative transient hypocalcemia. On histologic examination, thyroid carcinoma was identified in 3 of 88 cats. Hyperthyroidism recurred in 5 cats between 3 and 59 months; 4 of these cats had EHTT preoperatively. The difference in recurrence rate between hyperthyroid cats with and without EHTT was significant (P<.001). CONCLUSION: Complications were uncommon after thyroidectomy performed by an experienced surgeon when combined with an anesthetic regimen associated with minimal adverse cardiovascular effects. Hyperthyroid cats with EHTT had a significantly higher chance of recurrence. CLINICAL RELEVANCE: Thyroidectomy is associated with a low incidence of surgical complications and is an effective treatment for hyperthyroid cats when radioactive iodine therapy is not available. Preoperative thyroid scintigraphy is advised. Surgery is not recommended when EHTT is present, because of a higher chance of developing recurrent disease.     

Hyperthyroidism associated with a thyroid adenoma in a dog

Hyperthyroidism associated with thyroid adenoma was diagnosed in a dog. Typical clinical signs of hyperthyroidism were resolved with surgical excision of the adenoma. Hyperthyroidism in dogs usually is associated with thyroid carcinoma, which has a poor prognosis. This case emphasizes the importance of obtaining a histologic diagnosis of thyroid tumors in hyperthyroid dogs before giving a prognosis.     

Plasma asymmetric dimethylarginine, symmetric dimethylarginine, l-arginine, and nitrite/nitrate concentrations in cats with chronic kidney disease and hypertension

BACKGROUND: Chronic kidney disease (CKD) and hypertension have been associated with decreased bioavailability of nitric oxide (NO) and endothelial dysfunction. Increased concentrations of the endothelial nitric oxide synthase (eNOS) inhibitor asymmetric dimethylarginine (ADMA) are implicated. HYPOTHESIS: Plasma ADMA concentration is increased in cats with CKD and systemic hypertension corresponding to a decrease in total plasma nitrate/nitrite (NOx) availability. Decrease in systolic blood pressure (SBP) and proteinuria during treatment of hypertension with amlodipine besylate may be associated with increased NOx availability. ANIMALS: Sixty-nine client-owned normotensive and hypertensive cats with variable azotemia. METHODS: Plasma ADMA, symmetric dimethylarginine (SDMA), and l-arginine were measured simultaneously by hydrophilic-interaction liquid chromatography-electrospray tandem mass spectrometry in cats from 6 groups: normotensive nonazotemic (n = 10), normotensive mildly azotemic (n = 10), hypertensive mildly azotemic with hypertensive retinopathy (n = 20), hypertensive mildly azotemic without hypertensive retinopathy (n = 10), normotensive moderately azotemic cats (n = 10), and hypertensive nonazotemic cats (n = 9). Plasma NOx concentrations were measured. RESULTS: A moderate correlation between plasma creatinine and ADMA (n = 69, r= .608, P < .001), SDMA (n = 69, r= .741, P < .001), and NOx concentrations (n = 69, r= .589, P < .001) was observed. There was no association among plasma ADMA, SDMA, and NOx concentrations and SBP. CONCLUSIONS AND CLINICAL IMPORTANCE: Plasma ADMA and SDMA concentrations are increased in cats with CKD and correlate with plasma creatinine concentration. This may imply the presence of endothelial dysfunction in cats with CKD. Plasma ADMA concentrations were not associated with systemic hypertension. Treatment of systemic hypertension with amlodipine besylate did not affect plasma ADMA or NOx concentrations.     

Glucose tolerance and insulin secretion in spontaneously hyperthyroid cats

Glucose tolerance and insulin secretion after administration of a glucose load were determined in 11 clinically normal cats and 15 cats with spontaneous hyperthyroidism. In six hyperthyroid cats, a glucose tolerance test was repeated after treatment with radioactive iodine (131I). All cats had similar baseline glucose concentrations. However, the cats with hyperthyroidism had a significantly decreased glucose clearance, which was worse after treatment. Hyperthyroidism also caused a marked increase in basal and glucose-stimulated insulin secretion, which was not improved with treatment. It is concluded that hyperthyroidism in cats may lead to long-lasting alterations of glucose tolerance and insulin secretion which may not be reversed by treatment.     

Tolerability and efficacy of benazepril in cats with chronic kidney disease

The objective of the study was to test the effect of the angiotensin-converting enzyme inhibitor (ACEI) benazepril in cats with chronic kidney disease (CKD). A total of 192 cats with CKD with an initial plasma creatinine concentration > or = 2 mg/dL (> or = 177 micromol/L) and urine specific gravity < or = 1.025 were recruited into a double-blind, parallel-group, prospective, randomized clinical trial. Cats received daily (q24h) PO placebo (n = 96) or benazepril x HCl at a dosage of 0.5-1.0 mg/kg (n = 96) for up to 1,119 days. Most cats were fed exclusively a diet containing low amounts of phosphate, protein, and sodium. Benazepril produced a significant reduction in proteinuria, assessed by the urine protein-to-creatinine ratio (UPC, P = .005). This effect of benazepril was present in all subgroups tested, including cats with UPC <0.2, although the effect was largest in cats with higher UPCs. Plasma protein was maintained at higher concentrations with benazepril as compared with placebo during treatment in cats with initial UPC <1 (P = .038 versus P = .079 for all cats). There was no difference in renal survival time between the 2 groups when all 192 cats were compared. Mean +/- SD renal survival times were 637 +/- 480 days with benazepril and 520 +/- 323 days with placebo (P = .47). Mean +/- SD renal survival times in the 13 cats with initial UPC > or = 1 were 402 +/- 202 days with benazepril and 149 +/- 90 days with placebo (P = .27). Cats with initial UPC > or = 1 treated with benazepril had better appetite (P = .017) as compared with those treated with placebo. Benazepril was well tolerated. In conclusion, benazepril decreased proteinuria in cats with CKD.