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Stammeleer L, Xifra P, Serrano SI, Rishniw M, Daminet S, Peterson ME. Blood pressure in hyperthyroid cats before and after radioiodine treatment. J Vet Intern Med 2024; 38:1359-1369. [PMID: 38440934 PMCID: PMC11099771 DOI: 10.1111/jvim.17032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 02/16/2024] [Indexed: 03/06/2024] Open
Abstract
BACKGROUND Hyperthyroid cats commonly have systemic hypertension, with a reported prevalence of 7% to 48%. Although hypertension might be expected to resolve once treatment restores euthyroidism, it can persist or only first develop after treatment. OBJECTIVES To determine the proportion of hyperthyroid cats with hypertension (systolic blood pressure [SBP] ≥160 mm Hg), persistence or first development of hypertension after successful radioiodine treatment, and correlation of post-treatment hypertension with azotemia or hypothyroidism. ANIMALS Four hundred one hyperthyroid nonazotemic cats were included in the study. METHODS Prospective, cross-sectional and before-and-after studies. All hyperthyroid cats had SBP measured by Doppler; 255 had SBP rechecked 6 months after successful radioiodine (131I) treatment. RESULTS Of untreated hyperthyroid cats, 108/401 (27%) were hypertensive. A higher proportion of hypertensive cats were nervous/excited compared with normotensive cats (47% vs 12%; P < .001). Of the initially hypertensive cats, 87/108 cats were reexamined after 131I treatment; 43/87 (49%) cats normalized SBP, whereas 44/87 (51%) remained hypertensive. Of the initially normotensive cats, 16/168 (9.5%) first developed hypertension after successful 131I treatment. 7/60 (12%) of the 131I-treated hypertensive cats were azotemic and 9/60 (15%) were hypothyroid. A higher proportion of cats remaining hypertensive had nervous/excited demeanor than did normotensive cats (50% vs 17%; P < .001). CONCLUSIONS/CLINICAL IMPORTANCE Hypertension, when present, resolves in many hyperthyroid cats after successful treatment. Hyperthyroid cats uncommonly develop new hypertension after treatment. Persistent or newly detected hypertension was unrelated to azotemia or iatrogenic hypothyroidism. More frequently perceived nervousness/anxiety in radioiodine-treated hypertensive cats suggests that many of these cats might have "situational" hypertension, as hyperthyroid-induced hypertension should resolve after treatment.
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Affiliation(s)
- Lisa Stammeleer
- Small Animal Department, Faculty of Veterinary MedicineGhent UniversityMerelbekeBelgium
| | | | | | | | - Sylvie Daminet
- Small Animal Department, Faculty of Veterinary MedicineGhent UniversityMerelbekeBelgium
| | - Mark E. Peterson
- Cornell UniversityIthacaNew YorkUSA
- Animal Endocrine ClinicNew YorkNew YorkUSA
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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; 37:2039-2051. [PMID: 37668163 PMCID: PMC10658547 DOI: 10.1111/jvim.16849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 08/23/2023] [Indexed: 09/06/2023] Open
Abstract
BACKGROUND Hyperthyroid cats often have urine specific gravity (USG) values <1.035. It remains unclear how USG changes after treatment, if USG can be used to predict azotemia after treatment, or how iatrogenic hypothyroidism influences USG values. OBJECTIVES To determine the proportion of hyperthyroid cats with USG <1.035 vs ≥1.035; if USG changes after treatment; and whether USG <1.035 correlated with unmasking of azotemia or hypothyroidism. ANIMALS Six hundred fifty-five hyperthyroid cats treated with radioiodine; 190 clinically normal cats. METHODS Prospective, before-and-after study. Hyperthyroid cats had serum thyroxine, thyroid-stimulating hormone, and creatinine concentrations, and USG measured before and 6 months after successful treatment with radioiodine. RESULTS Of untreated hyperthyroid cats, USG was ≥1.035 in 346 (52.8%) and <1.035 in 309 (47.2%). After treatment, 279/346 (80.6%) maintained USG ≥1.035, whereas 67/346 (19.4%) became <1.035; 272/309 (88%) maintained USG <1.035, whereas 37/309 (12%) became ≥1.035. Only 22/346 (6.4%) with USG ≥1.035 developed azotemia after treatment, compared with 136/309 (44%) with <1.035 (P < .001). Of cats remaining nonazotemic, 38% had USG <1.035, compared with 20% of normal cats (P < .001). The 137 cats with iatrogenic hypothyroidism had lower USG after treatment than did 508 euthyroid cats (1.024 vs 1.035), but USGs did not change after levothyroxine supplementation. USG <1.035 had high sensitivity (86.1%) but moderate specificity (65.2%) in predicting azotemia after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE Hyperthyroidism appears not to affect USG in cats. However, cats with evidence of sub-optimal concentrating ability before radioiodine treatment (USG < 1.035) are more likely to develop azotemia and unmask previously occult chronic kidney disease. Iatrogenic hypothyroidism itself did not appear to affect USG values.
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Affiliation(s)
- Mark E. Peterson
- Animal Endocrine Clinic, 21 West 100th StreetNew YorkNew YorkUSA
- College of Veterinary MedicineCornell UniversityIthacaNew YorkUSA
| | - Mark Rishniw
- College of Veterinary MedicineCornell UniversityIthacaNew YorkUSA
- Veterinary Information NetworkDavisCaliforniaUSA
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Prieto JM, Carney PC, Smith SM, Miller ML, Rishniw M, Randolph JF, Salerno VJ, Lamb SV, Place NJ, Farace G, Peterson S, Peterson ME. Biological variation of serum thyrotropin and thyroid hormones concentrations determined at 8-week intervals for 1 year in clinically healthy cats. Vet Clin Pathol 2023; 52:493-502. [PMID: 37528445 DOI: 10.1111/vcp.13251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 02/04/2023] [Accepted: 02/23/2023] [Indexed: 08/03/2023]
Abstract
BACKGROUND Cats commonly develop thyroid disease but little is known about the long-term biological variability of serum thyroid hormone and thyrotropin (thyroid-stimulating hormone; TSH) concentrations. OBJECTIVES We aimed to determine the long-term biological variation of thyroid hormones and TSH in clinically healthy cats. METHODS A prospective, observational study was carried out. Serum samples for analysis of total thyroxine (T4, by radioimmunoassay [RIA] and homogenous enzyme immunoassay [EIA]), triiodothyronine (T3 ), free T4 (by dialysis), and TSH were obtained every 8 weeks for 1 year from 15 healthy cats, then frozen until single-batch analysis. Coefficients of variation (CV) within individual cats (CV I ) and among individual cats (CV G ), as well as the variation between duplicates (ie, analytical variation [CV A ]) were determined with restricted maximum likelihood estimation. The indices of individuality (IoI) and reference change values (RCVs) for each hormone were calculated. RESULTS Some thyroid hormones showed similar (total T4 by EIA) or greater (TSH) interindividual relative to intraindividual variation resulting in intermediate to high IoI, consistent with previous studies evaluating the biological variation of these hormones weekly for 5-6 weeks. By contrast, total T4 (by RIA) and free T4 had a low IoI. Total T3 had a high ratio ofCV A toCV I ; therefore, interindividual variation could not be distinguished from analytical variation. No seasonal variability in the hormones could be demonstrated. CONCLUSIONS Clinicians might improve the diagnosis of feline thyroid disease by establishing baseline concentrations for analytes with intermediate-high IoI (total T4, TSH) for individual cats and applying RCVs to subsequent measurements.
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Affiliation(s)
- Jennifer M Prieto
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - Patrick C Carney
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - Stephanie M Smith
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - Meredith L Miller
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - Mark Rishniw
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - John F Randolph
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
| | - Valerie J Salerno
- Population Medicine & Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Steve V Lamb
- Population Medicine & Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Ned J Place
- Population Medicine & Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | | | | | - Mark E Peterson
- Departments of Clinical Sciences, Cornell University, Ithaca, New York, USA
- Animal Endocrine Clinic, New York, New York, USA
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Xifra P, Serrano SI, Peterson ME. Effect of radioiodine treatment on muscle mass in hyperthyroid cats. Vet Med (Auckl) 2022; 36:1931-1941. [PMID: 36200596 DOI: 10.1111/jvim.16560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 09/21/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Approximately 75% of hyperthyroid cats lose muscle mass as accessed with a muscle condition scoring (MCS) system. After treatment, MCS improves as the cats regain muscle mass. OBJECTIVES To quantify the degree of muscle loss in hyperthyroid cats using ultrasonography and evaluate changes in muscle mass after treatment. ANIMALS Forty-eight clinically normal cats and 120 cats with untreated hyperthyroidism, 75 of which were reevaluated after radioiodine-131 therapy. METHODS Prospective cross-sectional and before-after studies. All cats underwent ultrasonography and measurement of epaxial muscle height (EMH), with subsequent calculation of vertebral and forelimb epaxial muscle scores (VEMS and FLEMS). A subset of hyperthyroid cats underwent repeat muscle imaging 6 months after treatment. RESULTS Untreated hyperthyroid cats had a lower EMH than did clinically normal cats (median [25th-75th percentile], 0.98 [0.88-1.16] cm vs 1.34 [1.23-1.58] cm, P < .001). Seventy-seven (64.2%) untreated cats had subnormal EMH. Similarly, compared to normal cats, hyperthyroid cats had lower VEMS (0.93 [0.84-1.07] vs 1.27 [1.18-1.39], P < .001) and FLEMS (1.24 [1.10-1.35] vs 1.49 [1.39-1.63], P < .001). After treatment, EMH increased (1.03 [0.89-1.03] cm to 1.33 [1.17-1.41] cm, P < .001), with abnormally low EMH normalizing in 36/41 (88%). Both VEMS (0.94 [0.87-1.10] to 1.21 [1.10-1.31], P < .001) and FLEMS (1.31 [1.17-1.40] to 1.47 [1.38-1.66], P < .001) also increased after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE Almost two-thirds of hyperthyroid cats have abnormally low muscle mass when measured quantitatively by ultrasound. Successful treatment restores muscle mass in >85% of cats. EMH provided the best means of quantitating muscle mass in these cats.
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Affiliation(s)
| | | | - Mark E Peterson
- Animal Endocrine Clinic, NYC, New York, New York, USA.,College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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Chow JLY, White J. Radioactive iodine dose and survival in cats with hyperthyroidism (2015-2020). J Feline Med Surg 2022; 24:1001-1007. [PMID: 34730466 PMCID: PMC10812325 DOI: 10.1177/1098612x211056837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Radioactive iodine (131I) is the preferred treatment for feline hyperthyroidism but neither the optimal 131I dose nor consistent predictors of post-treatment azotaemia have been determined. The aims of the study were to evaluate the relationships between: (1) 131I dose and survival; and (2) pretreatment and post-treatment serum creatinine concentration. METHODS Medical records of hyperthyroid cats treated with 131I at a single referral hospital were reviewed. Information regarding signalment, body weight, pretreatment and post-treatment serum total thyroxine concentration (TT4), serum creatinine concentration, 131I dose and survival were determined. Multivariable Cox proportional hazards analysis was used to identify variables associated with survival. Multivariable linear regression analysis was used to identify variables associated with post-treatment serum creatinine concentration. RESULTS One hundred and ninety-eight (79 male, 119 female) cats were treated for hyperthyroidism with 131I (median dose 138 MBq; interquartile range 92-168). Median survival time was 1153 days (range 16-1871). Post-treatment serum creatinine (P <0.001) and age (P = 0.049) were significantly associated with survival. Every 10 µmol/l increase in post-treatment serum creatinine concentration and every year increase in age was associated with a 1.07-fold (confidence interval [CI] 1.04-1.11) and 1.17-fold (CI 1.00-1.37) increase in the daily hazard of death, respectively. Pretreatment serum creatinine concentration was directly, and post-treatment serum TT4 concentration was inversely, associated with post-treatment serum creatinine concentration. Every 1 μmol/l increase in pretreatment serum creatinine concentration was associated with an increase in post-treatment serum creatinine concentration of 0.7 μmol/l (SE 0.17; P <0.001). Conversely, every 1 nmol/l decrease in post-treatment serum TT4 concentration was associated with a 1.2 μmol/l (SE 0.61; P <0.001) increase in post-treatment serum creatinine concentration. CONCLUSIONS AND RELEVANCE Post-treatment serum TT4 concentration was associated with post-treatment azotaemia, which was associated with survival. Although 131I dose was not directly associated with survival, dosing strategies that minimise post-treatment hypothyroidism and azotaemia could improve patient survival.
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Affiliation(s)
- Joyce LY Chow
- Joyce LY Chow BVSc, MANZCVS, CityU Veterinary Medical Centre, G/F-2/F, Trinity Towers, 339 Lai Chi Kok Road, Sham Shui Po, Kowloon, Hong Kong
| | - Joanna White
- Small Animal Specialist Hospital, Sydney, Australia
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Yu L, Lacorcia L, Johnstone T. Hyperthyroid cats and their kidneys: a literature review. Aust Vet J 2022; 100:415-432. [PMID: 35711100 PMCID: PMC9543258 DOI: 10.1111/avj.13179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 04/28/2022] [Accepted: 05/01/2022] [Indexed: 11/28/2022]
Abstract
Hyperthyroidism and chronic kidney disease (CKD) are common diseases of geriatric cats, and often occur concurrently. Thus, a thorough understanding of the influence of thyroid function on renal function is of significant value for all feline practitioners. Among other effects, hyperthyroidism causes protein catabolism and increases renal blood flow and glomerular filtration rate (GFR). These effects render traditional renal markers insensitive for the detection of CKD in cats with uncontrolled hyperthyroidism. Furthermore, the development of iatrogenic hypothyroidism with over treatment of hyperthyroidism can be detrimental to renal function and may negatively affect long-term survival. This review discusses important diagnostic considerations of feline hyperthyroidism, as well as key treatment modalities, with an emphasis on the use of radioiodine and the importance of post treatment monitoring of thyroid and renal parameters. In Australia, a common curative treatment for cats with benign hyperthyroidism (i.e. thyroid hyperplasia or adenoma) is a fixed dose of orally administered radioiodine, regardless of the serum total thyroxine concentration at the time of diagnosis. This review discusses the long term outcomes of this standard of care in comparison with current, relevant research literature from around the world. Finally, this review explores the use of symmetric dimethylarginine (SDMA) in assessing renal function before and after treatment in hyperthyroid cats. SDMA correlates well with GFR and creatinine in non-hyperthyroid cats, but our understanding of its performance in hyperthyroid cats remains in its infancy.
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Affiliation(s)
- L Yu
- Veterinary Referral HospitalDandenongVictoriaAustralia
| | - L Lacorcia
- Veterinary Referral HospitalDandenongVictoriaAustralia
| | - T Johnstone
- Animal Referral Hospital, Essendon Fields72 Hargrave AvenueEssendon FieldsVictoria3041Australia
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Xifra P, Serrano SI, Peterson ME. Radioiodine treatment of hyperthyroidism in cats: results of 165 cats treated by an individualised dosing algorithm in Spain. J Feline Med Surg 2022; 24:e258-e268. [PMID: 35748791 PMCID: PMC10812264 DOI: 10.1177/1098612x221104743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVES Although radioiodine (131I) is the treatment of choice for feline hyperthyroidism, 131I-dosing protocols commonly induce iatrogenic hypothyroidism and expose azotaemia. A recently reported patient-specific 131I dosing algorithm minimised the risk of 131I-induced hypothyroidism and azotaemia, while maintaining high cure rates. The aim of the study was to report results of 131I treatment in a European population of hyperthyroid cats using this patient-specific dosing algorithm. METHODS This prospective case series (before-and-after study) evaluated 165 hyperthyroid cats referred for 131I treatment. All cats had serum concentrations of thyroxine (T4), triiodothyronine (T3) and thyroid-stimulating hormone (TSH) measured (off methimazole ⩾1 week). Thyroid volume and percentage uptake of 99mTc-pertechnetate (TcTU) were determined using thyroid scintigraphy. An initial 131I dose was calculated by averaging dose scores for T4/T3 concentrations, thyroid volume and TcTU; 70% of that composite dose was then administered. Twenty-four hours later, percentage 131I uptake was measured, and additional 131I administered as needed to deliver an adequate radiation dose to the thyroid tumour(s). Serum concentrations of T4, TSH and creatinine were determined 6-12 months later. RESULTS Median calculated 131I dose was 2.15 mCi (range 1.2-7.5), with only 51 (30.9%) receiving ⩾2.5 mCi. Of 165 cats, 124 (75.2%) became euthyroid, seven (4.2%) became overtly hypothyroid, 27 (16.4%) became subclinically hypothyroid and seven (4.2%) remained hyperthyroid. A higher proportion of overtly (85.7%) and subclinically (26.9%) hypothyroid cats developed azotaemia than euthyroid cats (13.6%; P = 0.0002). Hypothyroid cats were older (P = 0.016) and more likely to have detectable TSH concentrations (P = 0.025) and symmetrical bilateral distribution of 99mTc-pertechnetate uptake (P = 0.0002), whereas persistently hyperthyroid cats had higher severity scores (P = 0.012). CONCLUSIONS AND RELEVANCE Our results confirm that 131I dosing with this new algorithm results in high cure rates, with a lowered prevalence of 131I-induced overt hypothyroidism and azotaemia. Age, serum TSH concentrations, bilateral, symmetrical uptake and severity score help predict outcome.
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Affiliation(s)
| | | | - Mark E Peterson
- Animal Endocrine Clinic, New York, NY, USA
- Cornell University, Ithaca, NY, USA
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Urbanschitz T, Burgener IA, Zeugswetter FK. Utility of a canine TSH assay for diagnosis and monitoring of feline hyperthyroidism. TIERARZTLICHE PRAXIS. AUSGABE K, KLEINTIERE/HEIMTIERE 2022; 50:93-100. [PMID: 35523163 DOI: 10.1055/a-1807-9546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
OBJECTIVE This retrospective study was initiated to evaluate the utility of TSH measurements using a common canine TSH assay to diagnose and monitor feline hyperthyroidism after radioiodine or thyreostatic drug treatment. MATERIAL AND METHODS The electronic database of the University of Veterinary Medicine Vienna was searched for combined TSH and T4 measurements. 217 pairs of TSH and T4 from 136 cats with possible hyperthyroidism were assigned to group A (untreated; n = 24) and B (treated; n = 193). Measurements in group B were then subcategorized according to T4 concentrations (reference range 15-50 nmol/L): group B1 = elevated T4 (n = 46), group B2 = normal T4 (n = 84) and group B3 = decreased T4 (n = 63). Group B2 was further divided into cats with low normal (group B2a; n = 35), medium normal (group B2b; n = 29) and high normal (group B2c; n = 20) T4 concentrations. RESULTS TSH was detectable in 4 (17 %) of the 24 untreated cats (group A) and did not return to normal despite seemingly successful therapy in two. Increased TSH concentrations were observed in 3.6 % of the treated cats in group B2 and 2.9 %, 6.9 %, and 0 % in subgroups B2a, B2b and B2c, respectively. Forty-four percent of the treated cats with a decreased T4 (group B3) had an increased TSH concentration. TSH correlated with treatment length (r = 0.358, p = 0.004) and was significantly higher in cats treated for more than 3 months (p = 0.008). CONCLUSION TSH was detectable in a significant number of untreated hyperthyroid cats and thus this parameter should not be used to definitively rule out feline hyperthyroidism. Furthermore, the very low prevalence of increased TSH concentrations in treated hyperthyroid cats with a normal T4 and cost benefit calculations do not support the routine measurement of TSH in these cats. The fact that TSH correlated with time since treatment start and 56 % of the cats with a decreased T4 had TSH concentrations within the reference limits, suggests delayed recovery of the pituitary thyrotrophs which might explain the low prevalence of subclinical hypothyroidism in the present study. CLINICAL RELEVANCE TSH measurement in cats with suspected or treated hyperthyroidism using a canine assay lacks diagnostic sensitivity and can only complement therapeutic decision-making.
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Affiliation(s)
| | - Iwan A Burgener
- Department for Small Animals and Horses, University of Veterinary Medicine, Division of small animal internal medicine
| | - Florian K Zeugswetter
- Department for Small Animals and Horses, University of Veterinary Medicine, Division of small animal internal medicine
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Peterson ME, Rishniw M. A dosing algorithm for individualized radioiodine treatment of cats with hyperthyroidism. J Vet Intern Med 2021; 35:2140-2151. [PMID: 34351027 PMCID: PMC8478068 DOI: 10.1111/jvim.16228] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/02/2021] [Accepted: 07/13/2021] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Radioiodine (131 I) is the treatment of choice for hyperthyroidism in cats, but current 131 I-dosing protocols can induce iatrogenic hypothyroidism and expose azotemia. OBJECTIVES To develop a cat-specific algorithm to calculate the lowest 131 I dose to resolve hyperthyroidism, while minimizing risk of iatrogenic hypothyroidism and subsequent azotemia. ANIMALS One thousand and four hundred hyperthyroid cats treated with 131 I. METHODS Prospective case series (before-and-after study). All cats had serum concentrations of thyroxine (T4 ), triiodothyronine (T3 ), and thyroid-stimulating hormone (TSH) measured (off methimazole ≥1 week). Using thyroid scintigraphy, each cat's thyroid volume and percent uptake of 99m Tc-pertechnatate (TcTU) were determined. An initial 131 I dose was calculated by averaging dose scores for T4 /T3 concentrations, thyroid volume, and TcTU; 80% of that composite dose was administered. Twenty-four hours later, percent 131 I uptake was measured, and additional 131 I administered, as needed, to deliver an adequate radiation dose to the thyroid tumor(s). Serum concentrations of T4 , TSH, and creatinine were determined 6 to 12 months later. RESULTS The median calculated 131 I dose was 1.9 mCi (range, 1.0-10.6 mCi); 1380 cats required additional 131 I administration on day 2. Of the cats, 1047 (74.8%) became euthyroid, 57 (4.1%) became overtly hypothyroid, 240 (17.1%) became subclinically hypothyroid, and 56 (4%) remained hyperthyroid. More overtly (71.9%) and subclinically (39.6%) hypothyroid cats developed azotemia than euthyroid cats (14.2%; P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE Our algorithm for calculating individual 131 I doses resulted in cure rates similar to historical treatment rates, despite much lower 131 I doses. This algorithm appears to lower prevalence of both 131 I-induced overt hypothyroidism and azotemia.
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Affiliation(s)
- Mark E Peterson
- Animal Endocrine Clinic, New York, New York, USA.,College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Mark Rishniw
- College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.,Veterinary Information Network, Davis, California, USA
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10
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Alonzi C, Peak K, Gower L, Walker DJ, Johnson B. Establishing levels of retained radioactivity in cats receiving radioactive iodine treatment. Vet Rec 2021; 189:e196. [PMID: 33818767 DOI: 10.1002/vetr.196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 01/22/2021] [Accepted: 02/05/2021] [Indexed: 11/09/2022]
Abstract
BACKGROUND Radioactive iodine (RAI) is considered the gold standard treatment for feline hyperthyroidism. Currently exposure limits to radiation are regulated by national legislation, therefore the length of the isolation period in hospital for cats receiving radioactive treatment varies according to the place where the radioactive facility is located. The aim of this study was to establish when retained radioactivity decreases in cats receiving subcutaneous I-131 to a level that would allow discharge of cats from the hospital while being compliant with current United Kingdom legislation. METHODS Clinical records of cats treated with subcutaneous I-131 were retrospectively reviewed. Radioactive emission rates were measured using an external probe. Retained radioactivity below 11 MBq at the point of discharge was required by the initial risk assessment to ensure that a 0.3 mSv dose constraint was maintained for owners following standard cat-owner contact restrictions. Average retained activity for each treatment regimen at the time of discharge was calculated. The biological half-life for iodine retention was also calculated. RESULTS Overall, an end activity below 11 MBq was reached at day 11 in 49% of cats, and at day 13 in 91% of cats. These cats were allowed to be discharged according to UK legislation, as long as contact restrictions were applied at home for 2 weeks. CONCLUSION Based on our study, an isolation period of 13 days before allowing discharge of cats treated with subcutaneous RAI (I-131) is compliant with current UK legislation.
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Affiliation(s)
- Consuelo Alonzi
- Department of Internal Medicine, Anderson Moores Veterinary Specialists, Winchester, Hampshire, UK
| | - Kerry Peak
- Department of Internal Medicine, Anderson Moores Veterinary Specialists, Winchester, Hampshire, UK
| | - Lou Gower
- Department of Internal Medicine, Anderson Moores Veterinary Specialists, Winchester, Hampshire, UK
| | - David John Walker
- Department of Internal Medicine, Anderson Moores Veterinary Specialists, Winchester, Hampshire, UK
| | - Ben Johnson
- Southampton University Hospitals NHS Trust, Southampton, Hampshire, UK
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Stammeleer L, Buresova E, Stock E, Feenstra L, Vandermeulen E, Duchateau L, Van de Maele I, Daminet S. Comparison of free thyroxine measurement by chemiluminescence and equilibrium dialysis following 131I therapy in hyperthyroid cats. J Feline Med Surg 2020; 22:1114-1120. [PMID: 32228286 PMCID: PMC10814361 DOI: 10.1177/1098612x20906929] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2020] [Indexed: 11/15/2022]
Abstract
OBJECTIVES The first objective was to assess correlation between free thyroxine (fT4) measurements by equilibrium dialysis (fT4ED; Antech Diagnostics) and a chemiluminescent enzyme immunoassay (fT4CEIA; IMMULITE 2000 Veterinary Free T4 [Siemens Healthcare Diagnostics Products]) in hyperthyroid, otherwise healthy, cats before (T0), and 1 month (T1) and 11-23 months (T2) after radioactive iodine (131I) therapy. The second objective was to determine correlation between thyroid status based on fT4 (by both techniques) and the gold standard, thyroid scintigraphy. METHODS Thyroid status, including thyroid-stimulating hormone (TSH), total thyroxine (TT4) and fT4 serum concentrations, were assessed in 45 client-owned hyperthyroid cats before (T0), and 1 month (T1) and 11-23 months (T2) after 131I therapy. fT4 was determined by a chemiluminescent enzyme immunoassay (CEIA) and equilibrium dialysis (ED). Quantitative thyroid scintigraphy (with sodium 99m-Tc-pertechnetate) was performed at T2. RESULTS Spearman correlation between fT4CEIA and fT4ED was 0.81, 0.88 and 0.79 at T0, T1 and T2, respectively. fT4CEIA was consistently lower than fT4ED, with a median difference of -5.4 pmol/l (P <0.001) and -4.9 pmol/l (P <0.0001) at T1 and T2, respectively. At T2, all cats were identified as euthyroid based on thyroid scintigraphy. None of the cats were identified as being hypothyroid, based on serum TT4 and TSH measurements. Nine of 22 (40.9%) cats had an fT4CEIA below the reference interval (RI) at T2, whereas only 2/22 (9.1%) cats had an fT4ED concentration below the RI at T2. CONCLUSIONS AND RELEVANCE Good correlation exists between both assays at T1 and T2, but a significant systematic difference is noted at both time points. This could be an indication for reconsideration of the current RI, although further studies are warranted for assessing test accuracy (in otherwise healthy cats and cats with non-thyroidal illness). At this time, routine use of fT4CEIA after 131I therapy is not advised in feline patients.
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Affiliation(s)
- Lisa Stammeleer
- Small Animal Department, Ghent University, Merelbeke, Belgium
| | - Eva Buresova
- Small Animal Department, Ghent University, Merelbeke, Belgium
| | - Emmelie Stock
- Department of Medical Imaging of Domestic Animals, Ghent University, Merelbeke, Belgium
| | - Laurien Feenstra
- Department of Clinical Sciences of Companion Animals, Utrecht University, Utrecht, The Netherlands
| | - Eva Vandermeulen
- Department of Medical Imaging of Domestic Animals, Ghent University, Merelbeke, Belgium
| | - Luc Duchateau
- Biometrics Research Group, Ghent University, Merelbeke, Belgium
| | | | - Sylvie Daminet
- Small Animal Department, Ghent University, Merelbeke, Belgium
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12
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Wakeling J, Hall T, Williams TL. Correlation of thyroid hormone measurements with thyroid stimulating hormone stimulation test results in radioiodine-treated cats. J Vet Intern Med 2020; 34:2265-2275. [PMID: 33044029 PMCID: PMC7694841 DOI: 10.1111/jvim.15909] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 09/02/2020] [Accepted: 09/15/2020] [Indexed: 02/06/2023] Open
Abstract
Background Iatrogenic hypothyroidism can develop after radioiodine‐I131 (RAI) treatment of hyperthyroid cats and can be diagnosed using the thyroid stimulating hormone (TSH) stimulation test. Objectives To assess the effect of noncritical illness on TSH stimulation test results in euthyroid and RAI‐treated cats. To assess the correlation of low total‐thyroxine (tT4), low free‐thyroxine (fT4), and high TSH concentrations with TSH stimulation test results. Animals Thirty‐three euthyroid adult cats and 118 client‐owned cats previously treated with RAI. Methods Total‐thyroxine, fT4, and TSH were measured, and a TSH stimulation test was performed in all cats. Euthyroid control cats were divided into apparently healthy and noncritical illness groups. RAI‐treated cats were divided into RAI‐hypothyroid (after‐stimulation tT4 ≤ 1.5 μg/dL), RAI‐euthyroid (after‐stimulation tT4 ≥ 2.3 μg/dL OR after‐stimulation tT4 1.5‐2.3 μg/dL and before : after tT4 ratio > 1.5), and RAI‐equivocal (after stimulation tT4 1.5‐2.3 μg/dL and tT4 ratio < 1.5) groups. Results Noncritical illness did not significantly affect the tT4 following TSH stimulation in euthyroid (P = .38) or RAI‐treated cats (P = .54). There were 21 cats in the RAI‐equivocal group. Twenty‐two (85%) RAI‐hypothyroid cats (n = 26) and 10/71 (14%) of RAI‐euthyroid cats had high TSH (≥0.3 ng/mL). Twenty‐three (88%) RAI‐hypothyroid cats had low fT4 (<0.70 ng/dL). Of the 5 (7%) RAI‐euthyroid cats with low fT4, only one also had high TSH. Only 5/26 (19%) RAI‐hypothyroid cats had tT4 below the laboratory reference interval (<0.78 μg/dL). Conclusions and Clinical Relevance The veterinary‐specific chemiluminescent fT4 immunoassay and canine‐specific TSH immunoassay can be used to aid in the diagnosis of iatrogenic hypothyroidism in cats.
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Affiliation(s)
| | - Teresa Hall
- North West Nuclear Medicine, Vancouver, British Columbia, Canada
| | - Timothy L Williams
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
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13
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Peterson ME, Davignon DL, Shaw N, Dougherty E, Rishniw M, Randolph JF. Serum thyroxine and thyrotropin concentrations decrease with severity of nonthyroidal illness in cats and predict 30-day survival outcome. J Vet Intern Med 2020; 34:2276-2286. [PMID: 33001488 PMCID: PMC7694795 DOI: 10.1111/jvim.15917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 09/12/2020] [Accepted: 09/18/2020] [Indexed: 12/19/2022] Open
Abstract
Background In cats, nonthyroidal illness affects serum thyroid hormone concentrations. Serum thyroxine (T4) and triiodothyronine (T3) concentrations commonly decrease, whereas free T4 (fT4) concentrations vary unpredictably. Limited information exists regarding effects on serum thyrotropin (thyroid‐stimulating hormone [TSH]) concentrations in cats with nonthyroidal illness syndrome (NTIS). Objectives To characterize alterations in thyroid function that develop in cats with NTIS and to correlate these alterations with severity and outcome of the nonthyroidal illness. Animals Two hundred and twenty‐two cats with NTIS and 380 clinically normal cats of similar age and sex. Methods Prospective, cross‐sectional study. All cats had serum T4, T3, free T4, and TSH concentrations measured. Cats were grouped based on illness severity and 30‐day survival. Results Cats with NTIS had lower serum T4 and T3 concentrations than did normal cats (P < .001). Serum fT4 and TSH concentrations did not differ between groups. Serum T4, T3, and fT4 concentrations progressively decreased with increasing disease severity (P < .001). The 56 cats that died had lower T4, T3, and TSH concentrations than did the 166 survivors, with no difference in fT4 concentration. Multivariable logistic regression modeling indicated that serum T4 and TSH concentrations both predicted survival (P < .02). Conclusions and Clinical Importance Cats with NTIS commonly develop low serum T4, T3, and TSH concentrations, the prevalence and extent of which increases with disease severity. Clinicians should consider evaluating thyroid function in cats with severe NTIS, because doing so could help determine probability of successful treatment responses before investing considerable time, effort, and finances in addressing the underlying disease.
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Affiliation(s)
- Mark E Peterson
- Animal Endocrine Clinic, New York, New York, USA.,College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | | | - Nicole Shaw
- Veterinary Emergency and Referral Group, Brooklyn, New York, USA
| | | | - Mark Rishniw
- College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.,Veterinary Information Network, Davis, California, USA
| | - John F Randolph
- College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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14
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Yu L, Lacorcia L, Finch S, Johnstone T. Assessment of treatment outcomes in hyperthyroid cats treated with an orally administered fixed dose of radioiodine. J Feline Med Surg 2020; 22:744-752. [PMID: 31680613 PMCID: PMC10814508 DOI: 10.1177/1098612x19884155] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES The aims of this study were to describe the treatment outcomes following oral administration of a fixed dose (138 MBq; 3.7 mCi) of radioiodine in hyperthyroid cats and to examine the correlation between total thyroxine (TT4) concentrations before and after treatment. METHODS This was a retrospective cohort study that documented the TT4 concentration and clinicopathological parameters at the time of diagnosis and after treatment. Logistic regression was used to assess the relationship between TT4 concentrations before and after treatment. The difference in pre- and post-treatment variables between cats that had TT4 concentrations below or within the reference interval (RI) was compared by the Mann-Whitney U-test. RESULTS Of 161 cats, 133 (82.6%) cats had TT4 concentrations within the RI, four (2.5%) cats had TT4 concentrations above the RI and 24 (14.9%) cats had TT4 concentrations below the RI after treatment. The severity of hyperthyroidism at diagnosis, as measured by the percentage of TT4 elevation above the upper limit of the RI, had no impact on the odds of cats having low TT4 concentrations after treatment (odds ratio 1.00; 95% confidence interval 0.96-1.05; P = 0.828). CONCLUSIONS AND RELEVANCE When using an orally administered fixed dose of radioiodine for the treatment of feline hyperthyroidism, TT4 concentrations at diagnosis cannot be used to predict TT4 concentrations after treatment. The proportion of cats with TT4 concentrations below the lower limit of the RI after treatment was 14.9%. Further work is required to optimise oral radioiodine dosing to achieve maximal euthyroid outcomes.
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Affiliation(s)
- Lucia Yu
- Translational Research and Small Animal Clinical Trial Study Group, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC, Australia
| | - Lauren Lacorcia
- Translational Research and Small Animal Clinical Trial Study Group, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC, Australia
| | - Sue Finch
- Statistical Consulting Centre, The University of Melbourne, VIC, Australia
| | - Thurid Johnstone
- Translational Research and Small Animal Clinical Trial Study Group, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC, Australia
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15
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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; 50:1065-1084. [PMID: 32665137 DOI: 10.1016/j.cvsm.2020.06.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In cats, hyperthyroidism can be treated in 4 ways: medical management with methimazole or carbimazole, nutritional management (low-iodine diet), surgical thyroidectomy, and radioactive iodine (131I). Each form of treatment has advantages and disadvantages that should be considered when formulating a treatment plan for the individual hyperthyroid cat. Medical and nutritional managements are considered "reversible" or palliative treatments, whereas surgical thyroidectomy and 131I are "permanent" or curative treatments. The author discusses how each treatment modality could be the optimal choice for a specific cat-owner combination and reviews the advantages and disadvantages of each treatment option.
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16
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Prieto JM, Carney PC, Miller ML, Rishniw M, Randolph JF, Lamb SV, Place NJ, Peterson ME. Short-term biological variation of serum thyroid hormones concentrations in clinically healthy cats. Domest Anim Endocrinol 2020; 71:106389. [PMID: 31731251 DOI: 10.1016/j.domaniend.2019.106389] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/20/2019] [Accepted: 08/27/2019] [Indexed: 01/24/2023]
Abstract
Thyroid disease is common in cats, but little is known about the biologic variability of serum thyroid hormone concentrations and its impact on diagnostic utility in either healthy cats or cats with thyroid disease. The purpose of this study was to determine the biological variation, index of individuality, and reference change values for thyroid hormones and thyroid-stimulating hormone (TSH) in clinically healthy cats. Serum samples for analysis of total thyroxine (T4), triiodothyronine (T3), free T4 by dialysis, and TSH were obtained weekly for 6 wk from 10 healthy cats, then frozen until single-batch analyzed. Data were evaluated for outliers, and we determined the CV within individual cats (CVI) and between individual cats (CVG) for each hormone and the variation between duplicates or analytical variation (CVA). The index of individuality and reference change values for each hormone were then calculated. Serum concentrations of total T4, free T4, T3, and TSH all showed greater variation between cats (CVG) than within cats (CVI). Total and free T4 had an intermediate index of individuality (1.1 and 1.2, respectively), suggesting that these hormones would be best evaluated by a combination of their population-based reference intervals and reference change values. Serum TSH concentrations had high index of individuality (1.8), suggesting this hormone would be best evaluated with reference change values rather than the population-based reference interval. Total T3 also had a high calculated index of individuality (1.8); however, T3 had high ratio of analytical variation (CVA) to within cat variation (CVI), so RCV could not be accurately calculated. This study demonstrates that clinically normal cats show considerable interindividual biological variation in serum thyroid hormone and TSH concentrations, whereas the intraindividual variability in hormone concentrations is much narrower. This suggests that for all serum thyroid hormones, but especially serum TSH and T3 concentrations, comparing individual cat's hormone results to a population-based reference interval may be misleading, especially in those with early or subclinical thyroid disease. Clinicians might improve the diagnosis of feline thyroid disease by establishing baseline concentrations of T4, free T4, T3, and TSH for individual cats (ideally when healthy) and applying reference change values to subsequent measurements.
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Affiliation(s)
- J M Prieto
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - P C Carney
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - M L Miller
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - M Rishniw
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - J F Randolph
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - S V Lamb
- Department of Population Medicine & Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - N J Place
- Department of Population Medicine & Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - M E Peterson
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA; Animal Endocrine Clinic, New York, NY, USA.
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17
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Fernandez Y, Puig J, Powell R, Seth M. Prevalence of iatrogenic hypothyroidism in hyperthyroid cats treated with radioiodine using an individualised scoring system. J Feline Med Surg 2019; 21:1149-1156. [PMID: 30667287 PMCID: PMC10814268 DOI: 10.1177/1098612x18822396] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
Abstract
OBJECTIVES The aim of this study was to report the prevalence of iatrogenic hypothyroidism, with or without azotaemia, based on the measurement of serum total thyroxine (T4), thyroid-stimulating hormone (TSH) and creatinine concentrations, in hyperthyroid cats undergoing radioiodine (131I) treatment where the 131I dose was calculated using a previously described scoring system. A secondary aim of the study was to determine the positive and negative predictive values of serum T4 and TSH concentrations obtained 19 days after treatment in order to predict the development of iatrogenic hypothyroidism 6-9 months after 131I treatment. METHODS Serum T4, TSH and creatinine concentrations were measured 19 days and 6-9 months after 131I treatment. The prevalence of iatrogenic hypothyroidism was assessed with the results obtained 6-9 months after 131I treatment. RESULTS The prevalence of overt and subclinical hypothyroidism 6-9 months after 131I treatment was 40.0% (22/55 cats) and 12.7% (7/55 cats). Overt hypothyroidism with azotaemia was diagnosed in 8/55 (14.5%) cats. The positive and negative predictive values for the prediction of the development of iatrogenic hypothyroidism 6-9 months after 131I treatment were 72.2% and 80.0%, respectively, for a low serum T4 concentration, and 75.0% and 44.6%, respectively, for an increased serum TSH concentration. CONCLUSIONS AND RELEVANCE The use of an individualised scoring system is effective in determining the 131I dose for the treatment of hyperthyroid cats. However, the prevalence of overt hypothyroidism was higher in comparison with other studies using different dosing protocols. Further studies comparing the efficacy of individualised scoring systems and different fixed doses to determine which method is superior are warranted.
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Affiliation(s)
- Yordan Fernandez
- Centre for Small Animal Studies, Animal Health Trust, Newmarket, UK
| | - Jordi Puig
- Centre for Small Animal Studies, Animal Health Trust, Newmarket, UK
| | - Roger Powell
- Powell Torrance Diagnostic Services, Higham Gobion, UK
| | - Mayank Seth
- Centre for Small Animal Studies, Animal Health Trust, Newmarket, UK
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18
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Peterson ME, Carothers MA, Gamble DA, Rishniw M. Spontaneous primary hypothyroidism in 7 adult cats. J Vet Intern Med 2018; 32:1864-1873. [PMID: 30294940 PMCID: PMC6271337 DOI: 10.1111/jvim.15239] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 04/10/2018] [Accepted: 05/15/2018] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Naturally occurring hypothyroidism in adult cats is rare, with only 4 cases reported. OBJECTIVES To describe the historical, clinical, laboratory, and scintigraphic features of adult cats with spontaneous hypothyroidism. ANIMALS Seven adult cats referred for suspected hypothyroidism. METHODS Prospective case series. We collected data on cats' signalment, clinical signs, results of physical examination, routine laboratory and thyroid hormone testing, and thyroid imaging (thyroid scintigraphy or ultrasound). We subsequently treated cats with levothyroxine and evaluated their response to treatment. RESULTS Cats ranged from 3.5 to 11 years, with no apparent breed predilection; 6/7 cats were male. Only 2/7 cats were initially tested because of signs of hypothyroidism (hair-coat changes, lethargy, obesity); others were tested for routine thyroid monitoring or palpable thyroid nodules. Four were azotemic (serum creatinine, 2.2-3.4 mg/dL). Six of the cats had low serum thyroxine (T4 ) and free T4 (fT4 ) concentrations, whereas all 7 cats had high thyroid-stimulating hormone (TSH) concentrations. In 6/7 cats, thyroid scintigraphy revealed bilateral goiter with intense radionuclide uptake; imaging showed no visible thyroid tissue in the other. After levothyroxine treatment, serum concentrations of T4 and fT4 increased and TSH fell; high serum creatinine normalized in azotemic cats; and repeat imaging showed reduction in goiter size. CONCLUSIONS AND CLINICAL IMPORTANCE Primary hypothyroidism develops in adult cats, with a higher prevalence than previously thought. Most cats appear to develop a goitrous form of hypothyroidism associated with thyroid hyperplasia, whereas thyroid atrophy appears to be less common. With levothyroxine replacement, clinical and laboratory abnormalities improve or resolve.
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Affiliation(s)
- Mark E. Peterson
- Animal Endocrine ClinicNew York
- College of Veterinary MedicineCornell UniversityIthacaNew York
| | | | | | - Mark Rishniw
- College of Veterinary MedicineCornell UniversityIthacaNew York
- Veterinary Information NetworkDavisCalifornia
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19
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Morré WA, Panciera DL, Daniel GB, Monroe WE, Werre S. Investigation of a novel variable dosing protocol for radioiodine treatment of feline hyperthyroidism. J Vet Intern Med 2018; 32:1856-1863. [PMID: 30328158 PMCID: PMC6271315 DOI: 10.1111/jvim.15296] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/03/2022] Open
Abstract
Background Radioiodine is the treatment of choice for hyperthyroidism in cats. The ideal method of dose determination of radioiodine remains controversial. Objective To compare a method of radioiodine dose determination that utilized thyroid scintigraphy with a standard fixed dose for treatment of hyperthyroidism. Animals Fifty‐seven and 23 client‐owned hyperthyroid cats in the variable and fixed dose groups, respectively. Methods Cats with a percent dose uptake using 99mTc‐pertechnetate uptake on thyroid scintigraphy <5%, 5%‐10%, and >10% were to receive 3, 3.5, or 4.5 millicuries (mCi) of radioiodine, respectively, administered SC. Radioiodine dose was adjusted according to thyroid gland size as determined by the thyroid:salivary size ratio and categorized as <5:1, 5‐10:1, and >10:1. If the thyroid size fell into a higher dosing category than the percent dose uptake, the dose was increased accordingly. Cats in the fixed dose group received 4.5 mCi. Six months after treatment, cats were determined to be euthyroid, hypothyroid, or hyperthyroid based on serum thyroxine and thyroid stimulating hormone concentrations. Results No difference in outcome was found between the variable and fixed dose treatment groups. Euthyroidism, hypothyroidism, and persistent hyperthyroidism developed in 61, 30, and 9% of cats in the fixed dose group compared to 58, 26, and 16%, respectively, in the variable dose group. Conclusions A variable dosing method of radioiodine based on percent dose uptake primarily and thyroid gland size secondarily did not improve outcome compared to a standard fixed dose method.
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Affiliation(s)
- Wendy A Morré
- Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia
| | - David L Panciera
- Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia
| | - Gregory B Daniel
- Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia
| | - William E Monroe
- Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia
| | - Stephen Werre
- Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia
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20
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Peterson M, Varela F, Rishniw M, Polzin D. Evaluation of Serum Symmetric Dimethylarginine Concentration as a Marker for Masked Chronic Kidney Disease in Cats With Hyperthyroidism. J Vet Intern Med 2018; 32:295-304. [PMID: 29377360 PMCID: PMC5787157 DOI: 10.1111/jvim.15036] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 09/28/2017] [Accepted: 11/30/2017] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Hyperthyroidism can complicate (mask) the diagnosis of chronic kidney disease (CKD) because it increases glomerular filtration rate and decreases body muscle mass, both of which can lower serum creatinine concentrations. Currently, there is no clinical test that can reliably predict which hyperthyroid cats have concurrent azotemic CKD that will become apparent after treatment of the hyperthyroidism. OBJECTIVES To investigate serum symmetric dimethylarginine (SDMA) concentration as a potential marker of masked azotemia in untreated hyperthyroid cats. ANIMALS Two hundred and sixty-two hyperthyroid cats and 206 aged-matched, clinically normal cats. METHODS Prospective study. We measured creatinine, urea nitrogen, SDMA, T4 , and TSH concentrations before and 1, 3, and 6 months after treatment with radioiodine (131 I) and classified 131 I-treated cats as azotemic or nonazotemic based on persistent, post-treatment creatinine concentrations >2.1 mg/dL. Groups were compared via nonparametric tests, and diagnostic accuracy was determined by receiver operating characteristic analysis and logistic regression. RESULTS No hyperthyroid cats were azotemic before treatment, but 42 (16%) became azotemic when rechecked at 4-8 months (median, 6 months) after 131 I treatment; of these, 14 had high SDMA concentrations before treatment. As a diagnostic test for pre-azotemic (masked) CKD in untreated hyperthyroid cats, SDMA showed a sensitivity of 33.3% and specificity of 97.7%. CONCLUSIONS AND CLINICAL IMPORTANCE Finding a high serum SDMA concentration in a hyperthyroid cat can help predict development of azotemia after treatment. The test has high diagnostic test specificity (few false-positive results) but relatively low sensitivity (fails to predict azotemia in most hyperthyroid cats).
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Affiliation(s)
- M.E. Peterson
- Animal Endocrine Clinic New YorkNY
- College of Veterinary Medicine Cornell UniversityIthacaNY
| | | | - M. Rishniw
- College of Veterinary Medicine Cornell UniversityIthacaNY
- Veterinary Information Network DavisCA
| | - D.J. Polzin
- University of Minnesota College of Veterinary Medicine St. PaulMN
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