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      Assessment of serum symmetric dimethylarginine and creatinine concentrations in hyperthyroid cats before and after a fixed dose of orally administered radioiodine

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          Serum symmetric dimethylarginine (SDMA) is a sensitive renal biomarker for detecting early chronic kidney disease (CKD) in nonhyperthyroid cats, but knowledge regarding its performance in hyperthyroid cats remains limited.


          To determine the relationship between serum SDMA, creatinine and total thyroxine (TT4) concentrations in hyperthyroid cats before (T0) and 3 months after (T1) receiving a PO fixed dose of radioiodine.


          Eighty client‐owned hyperthyroid cats.


          Prospective cohort study. Serum TT4, and SDMA, creatinine concentrations, and urine specific gravity were measured at T0 and T1. Nonparametric tests were used to determine the relationship among SDMA, and creatinine and TT4 concentrations. Agreement between SDMA and creatinine regarding CKD staging at both time points was assessed using Goodman and Kruskal's gamma statistic.


          Mean serum SDMA concentration increased after treatment of hyperthyroidism. However, 21 of 75 cats experienced a decrease in SDMA between T0 and T1, whereas creatinine decreased in only 2 cats. A moderate correlation between SDMA and creatinine was seen at T1 ( r = 0.53; P < .001) but not at T0 ( r = 0.13; P = .25). Where assessable at T1, poor agreement was observed between SDMA and creatinine and CKD stage (Goodman and Kruskal's gamma 0.20; P = .29).

          Conclusions and clinical importance

          Discordant outcomes between SDMA and creatinine after radioiodine treatment in cats with hyperthyroidism suggest extrarenal factors may interfere with the reliability of SDMA to adequately reflect renal function. As a result, SDMA should not be interpreted in isolation in hyperthyroid cats treated with radioiodine.

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          Most cited references 45

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          Comparison of Serum Concentrations of Symmetric Dimethylarginine and Creatinine as Kidney Function Biomarkers in Cats with Chronic Kidney Disease

          Background Symmetric dimethylarginine (SDMA) has been shown to be an accurate and precise biomarker for calculating estimated glomerular filtration rate (GFR) in humans, as well as a more sensitive biomarker than serum creatinine concentration (sCr) for assessing renal dysfunction. Objectives The purpose of this retrospective study was to report on the utility of measuring serum SDMA concentrations in cats for detection of chronic kidney disease (CKD) before diagnosis by conventional measurement of sCr. Animals Chronic kidney disease cats (n = 21) included those persistently azotemic for ≥3 months (n = 15), nonazotemic cats with GFR >30% decreased from median GFR of normal cats (n = 4), and nonazotemic cats with calcium oxalate kidney stones (n = 2). Healthy geriatric cats (n = 21) were selected from the same colony. Methods Symmetric dimethylarginine concentrations (liquid chromatography‐mass spectroscopy) and sCr (enzymatic colorimetry) were determined retrospectively from historical data or banked serum samples in azotemic cats or at the time GFR (iohexol clearance) was measured in nonazotemic cats. Results Serum SDMA (r = −0.79) and sCr (r = −0.77) concentrations were significantly correlated to GFR (both P < .0001). Symmetric dimethylarginine became increased before sCr in 17/21 cats (mean, 17.0 months; range, 1.5–48 months). Serum SDMA had higher sensitivity (100%) compared with sCr (17%), but lower specificity (91% versus 100%) and positive predictive value (86% versus 100%). Conclusion and Clinical Importance Using serum SDMA as a biomarker for CKD allows earlier detection of CKD in cats compared with sCr, which may be desirable for initiating renoprotective interventions that slow progression of CKD.
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            Correlation between severity of thyroid dysfunction and renal function.

            Renal function is profoundly influenced by thyroid status; however, this has not been studied in detail in human subjects. The purpose of the present study was to determine the relationship between renal function and thyroid status before and after treatment for hypothyroidism and hyperthyroidism, respectively. In 37 consecutive hypothyroid and 14 hyperthyroid patients renal function as measured by plasma creatinine and glomerular filtration rate (GFR) [based on the modification of diet in renal disease (MDRD) formula] was determined before treatment and after regaining euthyroidism. Renal function improved significantly during treatment of hypothyroidism and decreased during treatment of hyperthyroidism. There was a strong correlation between the change in thyroid status determined as the ratio log(10)(fT4 post-treatment/fT4 pretreatment) and the change in renal function as a result of therapy expressed as serum creatinine (r(2) = 0.81, P < 0.0001) and estimated GFR (0.69, P < 0.0001). The kidney is an important target of thyroid hormone action.
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              Relationship between lean body mass and serum renal biomarkers in healthy dogs

              Background Symmetric dimethylarginine (SDMA) is an accurate and precise biomarker for estimating glomerular filtration rate (GFR) in humans and cats. Serum creatinine (sCr) also correlates with GFR, but has limitations as a biomarker of renal function because nonrenal factors can influence its concentration. Hypothesis Differences in lean body mass (LBM) influence sCr, but not serum SDMA concentrations. Animals Forty‐one healthy Beagles, mean age 9.9 years (range: 3.1–14.8 years), were studied over a 6 month period. Methods Serum biomarkers of renal function were measured prospectively at baseline, and 1, 3, and 6 months. SDMA concentrations were measured by liquid chromatography‐mass spectroscopy and sCr concentrations by enzymatic colorimetry. Body composition was determined by dual energy x‐ray absorptiometry. Results LBM (P  females; P = .02). Mature adult dogs (<8 years) had greater LBM compared with geriatric dogs (≥8 years; P < .001). Conclusion and Clinical Importance sCr concentrations, but not SDMA concentrations, are influenced by LBM, which limits sCr utility as a biomarker for monitoring renal function in dogs with decreased LBM. Reductions in LBM can lower sCr concentration and overestimate GFR. SDMA concentrations, but not sCr concentrations were influenced by time on food. SDMA could have clinical advantages over sCr in monitoring response to nutritional interventions.

                Author and article information

                J Vet Intern Med
                J. Vet. Intern. Med
                Journal of Veterinary Internal Medicine
                John Wiley & Sons, Inc. (Hoboken, USA )
                07 June 2020
                July 2020
                : 34
                : 4 ( doiID: 10.1111/jvim.v34.4 )
                : 1423-1431
                [ 1 ] Translational Research and Small Animal Clinical Trial Study Group, Faculty of Veterinary and Agricultural Sciences The University of Melbourne Victoria Australia
                [ 2 ] Statistical Consulting Centre and Melbourne Statistical Consulting Centre The University of Melbourne Victoria Australia
                Author notes
                [* ] Correspondence

                Lucia Yu, Veterinary Referral Hospital, 36 Lonsdale Street, Dandenong, Victoria 3175, Australia.

                Email: lucia.yu@ 123456petreferrals.com.au

                © 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

                This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 2, Tables: 3, Pages: 9, Words: 8104
                Standard Article
                SMALL ANIMAL
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                Custom metadata
                July 2020
                Converter:WILEY_ML3GV2_TO_JATSPMC version:5.8.5 mode:remove_FC converted:24.07.2020

                Veterinary medicine

                azotemia, chronic kidney disease, ckd, feline, hyperthyroidism, i‐131


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