Introduction
Hyperthyroid cats frequently also have chronic kidney disease (CKD), with 15% to 50% of hyperthyroid cats reported to have concurrent CKD.1–5 However, diagnosing azotemic CKD in hyperthyroid cats can challenge clinicians because untreated hyperthyroidism increases renal blood flow (RBF) and glomerular filtration rate (GFR)6–9 and decreases body muscle mass,10,11 all of which can lower serum creatinine concentration to within its reference interval. Consequently, many hyperthyroid cats with concurrent (but masked) CKD only develop azotemia after successful treatment, when hyperthyroidism no longer maintains high RBF and GFR and lost muscle mass is restored.4,6,9–14
Multiple studies15–19 have established that cats with isolated CKD, even in International Renal Interest Society (IRIS) stage 2 or 3, have shortened survival times compared to similarly aged cats with normal kidney function. Similarly, while the reported median survival time for cats with hyperthyroidism ranges from 1.6 to 4.0 years,5,20–24 hyperthyroid cats that are overtly azotemic prior to treatment have shorter survival times, ranging from 0.5 to 2.0 years.5,20 In untreated hyperthyroid cats with normal serum creatinine concentrations, however, 1 study of a relatively small number of hyperthyroid cats rendered euthyroid with methimazole failed to observe a difference in survival times between cats that developed mild-to-moderate azotemia and cats that remained nonazotemic after treatment, provided that iatrogenic hypothyroidism was avoided.25 Subsequently, multiple authors have cited this apparent lack of difference in survival in review papers and book chapters.8,26–28 However, in a recent study24 of hyperthyroid cats treated with radioiodine, posttreatment serum creatinine concentration was negatively associated with survival after adjusting for age, suggesting that concurrent azotemia might indeed shorten long-term survival in cats with “masked” azotemic CKD.24
In this study, we sought to determine the long-term survival of a large group of hyperthyroid cats treated with radioiodine-131 (131I) to restore euthyroidism. We also wanted to determine whether hyperthyroid cats with concurrent, but masked, CKD have shorter survival times than do cats that remain nonazotemic after successful 131I treatment.
Methods
Study design and selection of animals
One thousand forty-seven hyperthyroid cats were evaluated in this study, all of which had been successfully treated with radioiodine and rendered euthyroid. The clinical details of these cats have been previously reported as part of a cohort of 1,400 131I-treated hyperthyroid cats, together with the full details of a 131I dosing algorithm and the initial 6- to 12-month follow-up results.29 In all cats treated with methimazole, the drug was discontinued > 1 to 2 weeks before treatment with 131I. All hyperthyroid cats with preexistent azotemia (defined as serum creatinine > 2 mg/dL) were excluded, either when hyperthyroid or when made euthyroid with methimazole.
On the day of treatment with radioiodine, each cat was weighed and had a body condition score (BCS) assigned with a 9-point scale (score of 5 ideal, ≤ 4 too thin, and ≥ 6 too heavy).30,31 Each cat was also assigned a muscle condition score with a 4-point scale (0 = severe muscle wasting, 1 = moderate wasting, 2 = mild wasting, and 3 = normal muscle mass).30,32
In our previous study,29 each cat’s thyroid status was classified into 1 of 3 categories based on the serum concentrations of T4 and thyroid-stimulating hormone (TSH) measured at 6 to 12 months (median, 6 months) after 131I treatment: euthyroid (1,047 cats [74.8%]), hypothyroid (297 cats [21.2%]), and persistently hyperthyroid (56 cats [4%]).29 For the present study, only the 1,047 euthyroid cats were included, and the hypothyroid and persistently hyperthyroid cats were excluded. These 131I-treated groups were excluded because of the known effects of hyper- and hypothyroidism on GFR and RBF,1,8 namely that persistent hyperthyroidism might continue to mask underlying renal azotemia, whereas iatrogenic hypothyroidism can result in prerenal azotemia caused by the lowered GFR and RBF.27,28,33
In the present study and our previous study,29 cats were classified as azotemic or nonazotemic at 6 to 12 months after 131I treatment (median time, 6 months), with renal azotemia defined as a serum creatinine concentration above our institution’s reference interval (> 2.0 mg/dL),33 together with inadequate urine-concentrating ability (urine specific gravity [USG] < 1.035).
Survival analysis
All hyperthyroid cats were initially treated and entered into the study over the period of January 2013 to June 2020.29 Cats were then followed up at 6- to 12-month intervals, receiving a complete physical examination, routine laboratory testing, and determination of serum thyroid hormone concentrations until their date of death, euthanasia, or loss to follow-up. If a cat was not rechecked in our clinic, we contacted the primary care veterinarian and owner for the cat’s follow-up test results and survival information. The last follow-up evaluation was done January 2024.
Survival time was defined as the date of 131I treatment to the date of death or euthanasia. Cats lost to follow-up were right-censored at the date they were last examined. Cats were categorized as lost to follow-up if they had not been rechecked either at our clinic or by the primary veterinarian for > 6 months and their owners could not be contacted by telephone or email. Cats were also right-censored if they were alive at the end of the study period (January 2024).
Data and statistical analyses
Data were assessed for normality by the D’Agostino-Pearson test and by visual inspection of graphical plots.34 Data were not normally distributed; therefore, all analyses used were performed with nonparametric tests. Results for continuous data (ie, age, body weight, serum T4, TSH, urea nitrogen, creatinine, and USG) are expressed as median (IQR).
Results for qualitative data are expressed as ratio (eg, breed, sex) or percent of cats (eg, prevalence of underweight, muscle wasting, methimazole use). Comparisons between 2 continuous variables between groups or within groups (before-after) were analyzed with the Mann-Whitney U test and Wilcoxon signed rank test, respectively. Categorical variables were compared between groups by the χ2 test or Fisher exact test as appropriate.
For the survival analysis, cats were grouped according to their renal status (azotemic or nonazotemic) at the 6- to 12-month follow-up after achieving euthyroidism. A Kaplan-Meier survival curve was created and median survival time determined for all cats, as well as azotemic and nonazotemic subgroups. The log-rank test was used to compare median survival times between the azotemic and nonazotemic groups of cats.35 A multivariable Cox proportional hazard model was used to identify whether azotemic status was independently associated with survival time after adjustment for potential confounding variables (ie, age, sex, breed, body weight, pretreatment and posttreatment serum concentrations of T4 and creatinine, and USG).36
For all analyses, statistical significance was defined as P ≤ .05. Statistical analyses were performed with proprietary statistical software (Prism, version 10.31; GraphPad Software; MedCalc, version 23.02; MedCalc Statistical Software Ltd).
Results
All cats with hyperthyroidism
The 1,047 hyperthyroid cats in this study ranged in age from 4 to 20 years (median, 12.0 years; Table 1). Breeds included domestic longhair and shorthair (931 cats [89.9%]), Maine Coon (32 cats), Siamese (27 cats), Bengal (7 cats), Burmese (7 cats), Norwegian Forest Cat (7 cats), Russian Blue (6 cats), Persian (5 cats), Ragdoll (4 cats), American Curl (2 cats), Manx (2 cats), Oriental Shorthair (2 cats), Siberian (2 cats), Tonkinese (2 cats), Abyssinian, Birman, Bombay, Chartreux, Devon Rex, Havana Brown, Himalayan, Korat, Ocicat, Scottish Fold, and Snowshoe (1 cat each). Of these, 527 (50.3%) were male and 520 (49.7%) were female; all had been neutered.
Comparisons of results for variables of interest for 1,047 client-owned hyperthyroid cats treated with radioiodine-131 between 2013 and 2020 to restore euthyroidism and subsequently (6 to 12 months later) classified as nonazotemic (n = 919) versus azotemic (128).
| Variable | All cats (1,047) | Nonazotemic (919) | Preazotemic (128) | P value |
|---|---|---|---|---|
| Age (y) | 12 (10–14) | 12 (10–13) | 13 (12–15) | < .0001 |
| Breed (mixed:purebred) | 931:116 (8.0) | 818:101 (8.1) | 113:15 (7.5) | .765 |
| Sex (female:male) | 521:526 (0.99) | 448:471 (0.95) | 73:55 (1.3) | .089 |
| Body weight (kg) | 4.5 (3.7–5.4) | 4.5 (3.7–5.4) | 4.15 (3.5–4.9) | .0004 |
| Underweight (BCS < 4/9) | 303 (28.8%) | 256 (27.8%) | 48 (37.5%) | .049 |
| Overweight (BCS > 5/9) | 147 (14%) | 137 (14.9%) | 10 (7.8%) | .030 |
| Muscle loss (MCS < 3/3) | 728 (69.5%) | 629 (68.4%) | 99 (77.3%) | .022 |
| Time from diagnosis (d) | 66 (31–194) | 67 (31–183) | 62 (30–322) | .545 |
| Prior methimazole use | 515 (49.2%) | 446 (48.5%) | 69 (52.9) | .259 |
| Pretreatment serum creatinine (mg/dL) | 1.1 (0.9–1.3) | 1.0 (0.8–1.2) | 1.5 (1.3–1.8) | < .0001 |
| Pretreatment SUN (mg/dL) | 26 (22–31) | 25 (21–30) | 34 (27–40) | < .0001 |
| Pretreatment urine specific gravity | 1.038 (1.022–1047) | 1.040 (1.027–1.049) | 1.019 (1.016–1.025) | < .0001 |
| Pretreatment serum T4 (µg/dL) | 8.9 (6.7–11.9) | 9.0 (6.7–11.9) | 8.4 (6.0–11.4) | .0581 |
| Pretreatment serum T3 (ng/dL) | 134 (89–210) | 135 (91–212) | 121 (83–196) | .123 |
| Time from treatment (mo) | 6.0 (6.0–7.0) | 6.0 (6.0–7.0) | 6.0 (6.0–7.0) | .335 |
| Posttreatment serum creatinine (mg/dL) | 1.6 (1.3–1.9) | 1.5 (1.3–18) | 2.5 (2.3–2.8) | < .0001 |
| Posttreatment SUN (mg/dL) | 30 (25–36) | 29 (24–34) | 43 (37–50) | < .0001 |
| Posttreatment serum T4 (µg/dL) | 1.9 (1.5–2.3) | 1.9 (1.5–2.3) | 1.8 (1.5–2.2) | .250 |
| Posttreatment serum TSH (ng/mL) | 0.07 (0.03–0.14) | 0.07 (0.03–0.14) | 0.09 (0.03–0.15) | .052 |
Continuous data are expressed as median (25th to 75th percentile) and analyzed with the Mann-Whitney test. Qualitative data are expressed as ratio (breed, sex) or percent (underweight, overweight, muscle loss, methimazole use) and analyzed with the Fisher exact test.
BCS = Body condition score. MCS = Muscle condition score. SUN = Serum urea nitrogen. TSH = Thyroid-stimulating hormone.
Cats weighed between 1.6 and 9.9 kg (median, 4.5 kg); 303 (29%) cats were considered underweight, 597 (57%) had an ideal BCS, and 147 (14%) were considered overweight. Muscle loss was detected in 728 cats (69.5%; Table 1). The time from diagnosis of hyperthyroidism to 131I treatment ranged from 6 days to 5 years (median, 66 days). Five hundred fifteen cats (49%) had never received methimazole treatment, and 532 cats (51%) had been treated with methimazole for a median time of 60 days.
Before 131I treatment, these cats had high serum concentrations of both T4 (median, 8.9 µg/dL; reference interval, 1.0 to 3.8 µg/dL) and T3 (median, 134 ng/dL; reference interval, 30 to 80 ng/dL).29 All cats had serum concentrations of creatinine that remained within (or below) our institution’s reference interval (0.8 to 2.0 mg/dL33; Table 1). Of the hyperthyroid cats, 421 of 821 (55.1%) had pretreatment USG values that were concentrated (≥ 1.035), and 369 of 821 (44.9%) had evidence for a decrease in renal concentrating ability (defined as USG < 1.035).
Hyperthyroid cats divided into preazotemic and nonazotemic groups
Of the 1,047 cats rendered euthyroid, 128 (12%) cats became azotemic after 131I treatment (median, 6.0 months; range, 1.0 to 9.5 months) and were presumed to have had concurrent, but masked, azotemic kidney disease at the time of diagnosis.29 All 128 of these cats had the diagnosis of CKD confirmed by documenting persistent azotemia on 2 or more consecutive occasions (rechecks at 1- to 6-month intervals) without evidence of a prerenal or postrenal cause. The remaining 919 euthyroid cats that had serum creatinine concentrations remaining ≤ 2.0 mg/dL were defined as nonazotemic.29
The 128 cats with preazotemic (masked) CKD did not differ from the 919 cats that remained nonazotemic in breed or sex distribution, time from diagnosis, prevalence of methimazole use, or serum T4 and T3 concentrations (Table 1). However, the 128 hyperthyroid cats with preazotemic (masked) CKD were older, weighed less, were thinner, and had a higher prevalence of muscle wasting than did the 919 nonazotemic cats. The preazotemic cats also had higher serum concentrations of creatinine and urea nitrogen and lower values for USG than did the cats that remained nonazotemic. A greater proportion of preazotemic cats than nonazotemic cats had USG values < 1.035 (108 of 121 [89.3%] vs 255 of 693 [36.8%]; P < .001). However, there was considerable overlap in the USG gravity and serum creatinine concentrations between the 2 groups (Supplementary Figure S1).
131I-treated euthyroid cats divided into azotemic and nonazotemic groups
Cats were reevaluated at a median time of 6.1 months after 131I treatment, with no difference in time from treatment between the cats that developed azotemic CKD and the nonazotemic cats (Table 1). After treatment, serum T4 concentrations decreased and serum TSH concentrations increased (P < .0001), with no difference in values between the azotemic and nonazotemic cats.
After treatment, serum creatinine and urea nitrogen concentrations increased in both azotemic and nonazotemic cats (P < .0001; Table 1). However, azotemic cats developed higher serum creatinine and urea nitrogen concentrations after treatment than did the nonazotemic cats (P < .0001).
Survival of 131I-treated euthyroid azotemic and nonazotemic cats
Of the 1,047 cats, 589 (56.3%) were euthanized or died prior to the study end point; 295 (28.2%) were alive at the end of the study, and 163 (15.6%) were lost to follow-up. Of the 589 cats that died during the study period, a greater proportion of azotemic cats died than did nonazotemic cats (97 of 128 [75.8%] vs 492 of 919 [53.5%]; P < .001).
Median survival time of all 1,047 euthyroid cats was 49.6 months (4.1 years). However, the 128 preazotemic cats had a shorter median survival time than did the 919 nonazotemic cats (34.1 months [2.8 years] vs 52.1 months [4.3 years]; P < .001; Figure 1).
Kaplan-Meier survival curves for 1,047 client-owned hyperthyroid cats treated with radioiodine-131 between 2013 and 2020 to restore euthyroidism and subsequently (6 to 12 months later) classified as azotemic (red; n = 128) versus nonazotemic (black; 919). Each step in a curve represents the death of ≥ 1 cat; tick marks represent cats that were censored. Median survival time was significantly (P < .0001) shorter for azotemic (34.1 months) versus nonazotemic (52.1 months) cats.
Citation: Journal of the American Veterinary Medical Association 2025; 10.2460/javma.24.10.0653
Renal disease, as the primary cause of death, occurred more commonly in azotemic cats than nonazotemic cats (68 of 97 [70.1%] vs 89 of 492 [18.1%]; P < .001). Of these 157 cats that died of renal disease, the 68 preazotemic cats developed azotemia earlier than did the 89 initially nonazotemic cats, as classified at 6 to 12 months after 131I (median, 6 months vs 30 months; P < .0001; Supplementary Figure S2). The 68 preazotemic cats also had a shorter survival time than did the 89 cats with late-onset azotemia (median, 29.5 months vs 42.3 months; P < .0001).
Multivariable Cox regression analysis showed that increasing age, male sex, and posttreatment renal status were independently associated with survival time (Table 2). Specifically, each additional year of age corresponded to a 21% increase in the hazard, while male sex was associated with a 43% increase in the hazard. After adjustment for age and sex, azotemic cats still had shorter survival times than nonazotemic cats.
Results of multivariable Cox regression analysis to identify variables associated with survival time for the 1,047 cats described in Table 1.
| Variable | Coefficient (SE) | Hazard ratio (95% CI) | P value | |
|---|---|---|---|---|
| All 1,047 cats | ||||
| Age (y) | 0.19 (0.02) | 1.21 (1.17–1.26) | < .0001 | |
| Breed (purebred) | –0.12 (0.13) | 0.88 (0.67–1.14) | .347 | |
| Sex (male) | 0.36 (0.09) | 1.43 (1.20–1.70) | < .0001 | |
| Body weight (kg) | –0.02 (0.03) | 0.98 (0.91–1.04) | .497 | |
| Masked azotemic CKD | 0.51 (0.12) | 1.21 (1.32–2.08) | < .0001 | |
| 919 nonazotemic cats | ||||
| Age (y) | 0.21 (0.02) | 1.24 (1.19–1.29) | < .0001 | |
| Breed (purebred) | –0.05 (0.15) | 0.96 (0.71–1.25) | .756 | |
| Sex (male) | 0.36 (0.09) | 1.43 (1.18–1.74) | .003 | |
| Body weight (kg) | –0.01 (0.03) | 0.99 (0.92–1.03) | .856 | |
| 128 azotemic cats | ||||
| Age (y) | 0.10 (0.05) | 1.11 (1.05–1.23) | .042 | |
| Breed (purebred) | –0.38 (0.35) | 0.68 (0.33–1.32) | .284 | |
| Sex (male) | 0.23 (0.21) | 1.26 (0.83–1.93) | .281 | |
| Body weight (kg) | –0.10 (0.09) | 0.90 (0.74–1.08) | .292 |
CKD = Chronic kidney disease.
Discussion
Our results indicate that hyperthyroid cats with concurrent, but masked, CKD that became azotemic by 6 to 12 months after 131I treatment have a shorter survival time than do treated cats that remain nonazotemic at this follow-up. The 131I-treated euthyroid, nonazotemic cats in this study had a median survival time of 4.3 years, similar to reported survival times of 131I-treated cats (3 to 4 years).20,23,24 However, euthyroid cats with masked azotemic CKD had a median survival time of 2.8 years—1.5 years shorter than that of euthyroid nonazotemic cats. Our findings are consistent with a recent study24 of 131I-treated cats, which also reported a negative association between posttreatment azotemia and survival.
Our finding that cats with masked CKD experience shorter survival times contrasted with an earlier study25 of hyperthyroid cats treated with antithyroid drugs (carbimazole or methimazole), which reported that development of mild-to-moderate CKD did not impact overall survival. In that study25 of 47 hyperthyroid cats treated with antithyroid drugs, however, the median survival time was only 794 days (2.2 years), much shorter than the 4.1 years observed in our cohort of 1,047 cats. While the reasons for this difference in survival rate are unclear, the medically treated cats were older than our 131I-treated cats (median age, 13.6 years vs 12 years), which may at least partly account for the differing results. Additionally, cats receiving 131I treatment have been reported to live longer than those treated with long-term antithyroid drugs,20 which may also explain the difference. Thus, in that study, a shorter survival of nonazotemic cats, rather than a longer survival of the azotemic cats, might explain the finding of “no difference.” On the other hand, the longer lifespans of our cats, which more closely matched previous studies of survival of nonazotemic cats rendered euthyroid, allowed for a clear distinction in survival between azotemic and nonazotemic cats. Importantly, both our study and the previous one25 excluded hyperthyroid cats that were clearly azotemic prior to treatment (serum creatinine > 2.0 mg/dL), as multiple investigators have identified that pretreatment azotemia decreases survival times in hyperthyroid cats.5,20,28
Similarly, multiple studies have demonstrated that cats with isolated CKD, even in IRIS stage 2 or 3, have shortened survival times compared to similarly aged cats with normal kidney function.15–19 Therefore, one could reasonably expect that concurrent CKD would adversely affect survival in hyperthyroid cats treated with 131I, as we observed. Most azotemic cats (70%) in this study died from renal disease; in contrast, only 19% of the nonazotemic cats eventually died from renal disease. This underscores the direct impact of CKD on survival outcomes and the need for clinicians to carefully monitor renal function in hyperthyroid cats after treatment, as development of azotemia may signal a poorer long-term prognosis.
In this study, both older age and male sex were linked to decreased survival in hyperthyroid cats, similar to findings from other studies of 131I-treated hyperthyroid cats.22–24 Specifically, each additional year of age corresponded to a 21% increase in the hazard, while male sex was associated with a 43% increase in the hazard (Table 2). While it may seem intuitive that increasing age correlates with shorter survival times in treated cats, the reason for reduced survival in male cats remains unclear, especially since all the cats in our study were neutered. Further research is needed to clarify these sex-based survival disparities in hyperthyroid cats treated with radioiodine. Although our azotemic cats were older than their nonazotemic counterparts (Table 1), this age-related hazard ratio did not sufficiently explain the survival differences between the 2 groups. Additionally, a high proportion (57%) of our azotemic cats were female, indicating that sex-related factors also could not account for the survival differences observed.
Based on the results of this study, predicting whether an untreated cat with hyperthyroidism has concurrent (but masked) CKD is crucial, as these cats tend to have shorter survival times. As we have previously reported, preazotemic hyperthyroid cats are more likely to exhibit serum creatinine concentrations in the upper third of the reference interval (> 1.3 mg/dL), and many of these cats will present with a USG that is dilute or poorly concentrated (< 1.035 and commonly even < 1.025).33,37 Therefore, clinicians should evaluate both USG and serum creatinine prior to treating the hyperthyroidism, as identifying a hyperthyroid cat likely to have masked azotemic CKD enables clinicians to tailor treatment decisions for both conditions.38
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
None reported.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
The authors have nothing to disclose.
ORCID
M. E. Peterson https://orcid.org/0000-0002-3016-1855
M. Rishniw https://orcid.org/0000-0002-0477-1780
References
- 1.↑
van Hoek I, Daminet S. Interactions between thyroid and kidney function in pathological conditions of these organ systems: a review. Gen Comp Endocrinol. 2009;160(3):205-215. doi:10.1016/j.ygcen.2008.12.008
- 2.
Conroy M, Brodbelt DC, O’Neill D, Chang YM, Elliott J. Chronic kidney disease in cats attending primary care practice in the UK: a VetCompassTM study. Vet Rec. 2019;184(17):526. doi:10.1136/vr.105100
- 3.↑
Geddes R, Aguiar J. Feline comorbidities: balancing hyperthyroidism and concurrent chronic kidney disease. J Feline Med Surg. 2022;24(7):641-650. doi:10.1177/1098612X221090390
- 4.↑
Riensche MR, Graves TK, Schaeffer DJ. An investigation of predictors of renal insufficiency following treatment of hyperthyroidism in cats. J Feline Med Surg. 2008;10(2):160-166. doi:10.1016/j.jfms.2007.10.005
- 5.↑
Williams TL, Peak KJ, Brodbelt D, Elliott J, Syme HM. Survival and the development of azotemia after treatment of hyperthyroid cats. J Vet Intern Med. 2010;24(4):863-869. doi:10.1111/j.1939-1676.2010.0550.x
- 6.↑
Boag AK, Neiger R, Slater L, Stevens KB, Haller M, Church DB. Changes in the glomerular filtration rate of 27 cats with hyperthyroidism after treatment with radioactive iodine. Vet Rec. 2007;161(21):711-715. doi:10.1136/vr.161.21.711
- 7.
van Hoek I, Lefebvre HP, Peremans K, et al. Short- and long-term follow-up of glomerular and tubular renal markers of kidney function in hyperthyroid cats after treatment with radioiodine. Domest Anim Endocrinol. 2009;36(1):45-56. doi:10.1016/j.domaniend.2008.10.001
- 8.↑
Vaske HH, Schermerhorn T, Grauer GF. Effects of feline hyperthyroidism on kidney function: a review. J Feline Med Surg. 2016;18(2):55-59. doi:10.1177/1098612X15575385
- 9.↑
Graves TK, Olivier NB, Nachreiner RF, Kruger JM, Walshaw R, Stickle RL. Changes in renal function associated with treatment of hyperthyroidism in cats. Am J Vet Res. 1994;55(12):1745-1749. doi:10.2460/ajvr.1994.55.12.1745
- 10.↑
Peterson ME, Castellano CA, Rishniw M. Evaluation of body weight, body condition, and muscle condition in cats with hyperthyroidism. J Vet Intern Med. 2016;30(6):1780-1789. doi:10.1111/jvim.14591
- 11.↑
Xifra P, Serrano SI, Peterson ME. Effect of radioiodine treatment on muscle mass in hyperthyroid cats. J Vet Intern Med. 2022;36(6):1931-1941. doi:10.1111/jvim.16560
- 12.
Becker TJ, Graves TK, Kruger JM, Braselton WE, Nachreiner RF. Effects of methimazole on renal function in cats with hyperthyroidism. J Am Anim Hosp Assoc. 2000;36(3):215-223. doi:10.5326/15473317-36-3-215
- 13.
Adams WH, Daniel GB, Legendre AM, Gompf RE, Grove CA. Changes in renal function in cats following treatment of hyperthyroidism using 131I. Vet Radiol Ultrasound. 1997;38(3):231-238. doi:10.1111/j.1740-8261.1997.tb00846.x
- 14.↑
DiBartola SP, Broome MR, Stein BS, Nixon M. Effect of treatment of hyperthyroidism on renal function in cats. J Am Vet Med Assoc. 1996;208(6):875-878. doi:10.2460/javma.1996.208.06.875
- 15.↑
Elliott J, Rawlings JM, Markwell PJ, Barber PJ. Survival of cats with naturally occurring chronic renal failure: effect of dietary management. J Small Anim Pract. 2000;41(6):235-242. doi:10.1111/j.1748-5827.2000.tb03932.x
- 16.
Syme HM, Markwell PJ, Pfeiffer D, Elliott J. Survival of cats with naturally occurring chronic renal failure is related to severity of proteinuria. J Vet Intern Med. 2006;20(3):528-535. doi:10.1111/j.1939-1676.2006.tb02892.x
- 17.
King JN, Tasker S, Gunn-Moore DA, Strehlau G; BENRIC (benazepril in renal insufficiency in cats) Study Group. Prognostic factors in cats with chronic kidney disease. J Vet Intern Med. 2007;21(5):906-916. doi:10.1111/j.1939-1676.2007.tb03042.x
- 18.
Boyd LM, Langston C, Thompson K, Zivin K, Imanishi M. Survival in cats with naturally occurring chronic kidney disease (2000-2002). J Vet Intern Med. 2008;22(5):1111-1117. doi:10.1111/j.1939-1676.2008.0163.x
- 19.↑
Gowan RA, Baral RM, Lingard AE, et al. A retrospective analysis of the effects of meloxicam on the longevity of aged cats with and without overt chronic kidney disease. J Feline Med Surg. 2012;14(12):876-881. doi:10.1177/1098612X12454418
- 20.↑
Milner RJ, Channell CD, Levy JK, Schaer M. Survival times for cats with hyperthyroidism treated with iodine 131, methimazole, or both: 167 cases (1996-2003). J Am Vet Med Assoc. 2006;228(4):559-563. doi:10.2460/javma.228.4.559
- 21.
Peterson ME, Becker DV. Radioiodine treatment of 524 cats with hyperthyroidism. J Am Vet Med Assoc. 1995;207(11):1422-1428. doi:10.2460/javma.1995.207.11.1422
- 22.↑
Slater MR, Geller S, Rogers K. Long-term health and predictors of survival for hyperthyroid cats treated with iodine 131. J Vet Intern Med. 2001;15(1):47-51.
- 23.↑
Vagney M, Desquilbet L, Reyes-Gomez E, et al. Survival times for cats with hyperthyroidism treated with a 3.35 mCi iodine-131 dose: a retrospective study of 96 cases. J Feline Med Surg. 2018;20(6):528-534. doi:10.1177/1098612X17718416
- 24.↑
Chow JL, White J. Radioactive iodine dose and survival in cats with hyperthyroidism (2015-2020). J Feline Med Surg. 2022;24(10):1001-1007. doi:10.1177/1098612X211056837
- 25.↑
Williams TL, Elliott J, Syme HM. Association of iatrogenic hypothyroidism with azotemia and reduced survival time in cats treated for hyperthyroidism. J Vet Intern Med. 2010;24(5):1086-1092. doi:10.1111/j.1939-1676.2010.0566.x
- 26.↑
Syme H. Are methimazole trials really necessary? In: Little SE, ed. August’s Consultations in Feline Internal Medicine. Vol 7. Elsevier; 2016:276-281.
- 27.↑
Williams T. Thyroid and kidney disease in cats. In: Feldman EC, Fracassi F, Peterson ME, eds. Feline Endocrinology. Edra Publishing; 2019:156-168.
- 28.↑
Yu L, Lacorcia L, Johnstone T. Hyperthyroid cats and their kidneys: a literature review. Aust Vet J. 2022;100(9):415-432. doi:10.1111/avj.13179
- 29.↑
Peterson ME, Rishniw M. A dosing algorithm for individualized radioiodine treatment of cats with hyperthyroidism. J Vet Intern Med. 2021;35(5):2140-2151. doi:10.1111/jvim.16228
- 30.↑
Freeman L, Becvarova I, Cave N, et al.; World Small Animal Veterinary Association Nutritional Assessment Guidelines Task Force Members. WSAVA nutritional assessment guidelines. J Small Anim Pract. 2011;52(7):385-396. doi:10.1111/j.1748-5827.2011.01079.x
- 31.↑
World Small Animal Veterinary Association Global Nutrition Committee. Body condition score. Updated August 13, 2020. Accessed November 15, 2024. https://wsava.org/wp-content/uploads/2020/08/Body-Condition-Score-cat-updated-August-2020.pdf
- 32.↑
World Small Animal Veterinary Association Global Nutrition Committee. Muscle condition score. Accessed November 15, 2024. https://wsava.org/wp-content/uploads/2020/01/Muscle-Condition-Score-Chart-for-Cats.pdf
- 33.↑
Peterson ME, Rishniw M. Urine concentrating ability in cats with hyperthyroidism: influence of radioiodine treatment, masked azotemia, and iatrogenic hypothyroidism. J Vet Intern Med. 2023;37(6):2039-2051. doi:10.1111/jvim.16849
- 34.↑
D’Agostino RB. Tests for normal distribution. In: D’Agostino RB, Stephens MA, eds. Goodness-of-Fit Techniques. Macel Dekker; 1986:367-420.
- 35.↑
D’Arrigo G, Leonardis D, Abd ElHafeez S, Fusaro M, Tripepi G, Roumeliotis S. Methods to analyse time-to-event data: the Kaplan-Meier survival curve. Oxid Med Cell Longev. 2021;2021(1):2290120. doi:10.1155/2021/2290120
- 36.↑
Abd ElHafeez S, D’Arrigo G, Leonardis D, Fusaro M, Tripepi G, Roumeliotis S. Methods to analyze time-to-event data: the Cox regression analysis. Oxid Med Cell Longev. 2021;2021(1):1302811. doi:10.1155/2021/1302811
- 37.↑
Peterson ME, Varela FV, Rishniw M, Polzin DJ. Evaluation of serum symmetric dimethylarginine concentration as a marker for masked chronic kidney disease in cats with hyperthyroidism. J Vet Intern Med. 2018;32(1):295-304. doi:10.1111/jvim.15036
- 38.↑
Peterson ME. Hyperthyroidism in cats: considering the impact of treatment modality on quality of life for cats and their owners. Vet Clin North Am Small Anim Pract. 2020;50(5):1065-1084. doi:10.1016/j.cvsm.2020.06.004
