Serum Total Thyroxine Concentrations Research Articles

Total thyroxine, triiodothyronine, and thyrotropin concentrations during acute nonthyroidal illness and recovery in dogs.

Acute illness can result in changes in serum total thyroxine (tT4), total triiodothyronine (tT3), and thyrotropin (TSH) concentrations in euthyroid dogs defined as nonthyroidal illness syndrome, but longitudinal evaluation of these hormones during the recovery phase is lacking. To longitudinally evaluate serum tT4, tT3, and TSH concentrations during the acute phase and recovery from acute illness in dogs. Nineteen euthyroid client-owned dogs hospitalized for acute illness at a veterinary teaching hospital. Prospective longitudinal study. Serum tT4, tT3, and TSH concentrations were measured at the admission (T0), at last day of hospitalization (T1), and during the recovery phase at 3, 7, 14, and 21 days after the discharge (T2, T3, T4, and T5), respectively. tT4 and tT3 were below the reference interval (RI) at T0 in 3 (16%) and 18 (95%) dogs, respectively; tT4 normalized in all dogs early in the recovery phase, while low tT3 persisted at the end of the study in 16 (83%) dogs. Median TSH concentrations were increased at T5 compared with T1 (0.19 ng/mL [range 0.03-0.65] vs 0.11 ng/mL [range (0.05-0.26)], mean difference = 0.09 ng/mL; P = .03). Five (26%) dogs had TSH above the RI at least at 1 time point during the recovery phase. None of the dogs had concurrent low tT4 and high TSH during the study. In euthyroid dogs acute illness can interfere with evaluation of thyroid function up to 21 days during the recovery phase. Thyroid testing should be avoided or postponed in these dogs.

Dietary hyperthyroidism in a dog with epileptic seizures

This report discusses a case of suspected dietary hyperthyroidism in a 2-year-old male crossbreed dog. The dog presented with a history of tonic-clonic seizures, seen over the previous 6 months, and was refractory to increasing doses of phenobarbitone. Serum total thyroxine concentrations were persistently elevated on repeated sampling; the rest of the investigations were normal. The initial diet – a raw food diet – was tested and found to contain detectable levels of total thyroxine. Dietary hyperthyroidism was therefore proposed as a potential cause of seizures in this case.

Hyperthyroid cats and their kidneys: a literature review.

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.

Radioactive iodine dose and survival in cats with hyperthyroidism (2015-2020).

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. 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. 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. 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.

Serial measurement of thyroid hormones in hospitalised dogs with canine parvoviral enteritis: Incidence of non-thyroidal illness syndrome and its association with outcome and systemic inflammatory response syndrome

The aim of this study was to serially evaluate the serum concentrations of total thyroxine (tT4), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) in dogs with canine parvoviral enteritis (CPVE) during a 5-day hospitalisation period and assess the association of these hormone concentrations with the outcome and the development of systemic inflammatory response syndrome (SIRS). Dogs with confirmed CPVE that were hospitalised for at least 5 days were included. The thyroid hormones concentrations were measured on days 1, 3 and 5 of hospitalisation.Twenty-eight dogs were included. All (28/28, 100%), 19/28 (69.7%) and 23/28 (82.1%) dogs had a low serum tT4, fT4 and TSH concentration, respectively, on at least 1 day during the hospitalisation period. Overall, 11/28 (39.3%) dogs were diagnosed with SIRS on at least 1 day. In survivors, serum tT4 concentration was significantly higher on day 5 (median, range: 11.8 nmol/L, <6.4–32.2 nmol/L) compared to those on days 1 (<6.4 nmol/L, <6.4–20.1 nmol/L; P = 0.010) or 3 (7.6 nmol/L, <6.4−25.2 nmol/L; P = 0.019). Survivors had a significantly higher tT4 concentration (median, range: 11.8 nmol/L, <6.4–32.2 nmol/L) on day 5 compared to non-survivors (<6.4 nmol/L, <6.4–7.2 nmol/L; P = 0.002). Regardless of the day of hospitalisation, dogs with SIRS had significantly lower tT4 (<6.4 nmol/L, <6.4–16.3 nmol/L) compared to dogs without SIRS (8.6 nmol/L, <6.4–32.2 nmol/L; P = 0.006). A significant difference was also found in fT4 between dogs with SIRS (<3.9 pmol/L, <3.9–16.2 pmol/L) and dogs without SIRS (15.1 pmol/L, <3.9−59.2; pmol/L; P < 0.001). Non-thyroidal illness syndrome was frequently observed in dogs with CPVE, and a negative association between tT4 and fT4 concentrations and SIRS was noted. Serial measurements of tT4 concentrations appeared to have prognostic value.

Sub‐epiglottic pharyngeal pouch remnant cyst in a 6‐month‐old female Labrador Retriever

AbstractA 6‐month‐old entire female Labrador Retriever was presented for intermittent respiratory rasping and rattling made worse with excitement and exercise, which appeared to be distressing for the patient. Clinical findings revealed a fluid‐filled cystic structure at the base of the tongue in a sub‐epiglottic position. Serum concentrations of total thyroxine, free thyroxine and thyroid‐stimulating hormone were within normal limits. A CT scan revealed a 2‐cm diameter spherical, encapsulated structure, filled with fluid attenuating material, positioned in the midline at the base of the tongue adjacent to the basihyoid. The cyst was surgically excised via an oral approach, and histopathological findings were suggestive of a pharyngeal pouch remnant cyst. There were no post‐surgical complications, and the dog made an unremarkable recovery. At 12‐month long‐term follow‐up, the owner reported that the dog remained fit and well showing no further signs of respiratory noise, exercise restriction or evidence of recurrence.

Serum Total Thyroxine Evaluation in Critically Ill Feline Patients.

This retrospective case control study compared serum total thyroxine (tT4) concentrations in hospitalized critical cats (CCs) and non-hospitalized cats with non-thyroidal chronic diseases (chronic group, CG) and evaluated the relationship between the serum tT4 concentration of CCs and systemic inflammation (systemic inflammatory response syndrome (SIRS)), disease severity (Acute Patient Physiologic and Laboratory Evaluation (APPLEfast)), and prognosis. Cats with previously suspected or diagnosed thyroid disease were excluded. Serum tT4 was evaluated in surplus serum samples at the time of admission for CCs and CGs. The APPLEfast score of the CC group was calculated at admission. The systemic inflammatory response syndrome (SIRS) in CCs was determined using proposed criteria. Cats were divided into survivors and non-survivors according to the discharge outcome. Forty-nine cats were retrospectively included. Twenty-seven cats died during hospitalization. The CG group was composed of 37 cats. The CC group showed a significantly lower tT4 compared to the CG group (1.3 ± 0.7 vs. 2 ± 0.9; p < 0.0001). Among SIRS, APPLEfast, and tT4, only tT4 was associated with mortality (p = 0.04). The tT4 cut-off point for mortality was 1.65 μg/dL (sensitivity 81%, specificity 57%, odds ratio (OR) 5.6). Twenty-five cats (51%) had SIRS that was not associated with tT4. Non-thyroidal illness syndrome can occur in critically ill cats and the evaluation of tT4 in hospitalized cats could add prognostic information.

Prognostic value of serum total thyroxine concentration at admission to an intensive care unit for critically ill dogs.

To determine whether serum total thyroxine (TT4) concentration at admission to an intensive care unit (ICU) was associated with mortality rate and duration of hospitalization for critically ill dogs. 166 client-owned dogs that were hospitalized in the ICU of a private veterinary practice from January 2013 through December 2016 and for which serum TT4 concentration had been measured at admission. Medical records were reviewed to collect data regarding patient signalment, concurrent illnesses, medications, reason for hospitalization, outcome (death, euthanasia, or survival to hospital discharge), duration of hospitalization, and initial serum TT4 concentration. Mean age of the 166 dogs was 8.6 years (range, 1 to 16 years). Overall mortality rate was 15.7%, with 26 dogs failing to survive to hospital discharge. Of these 26 dogs, 7 died and 19 were euthanized. No significant association was identified between serum TT4 concentration at admission and survival to discharge (yes or no) or duration of hospitalization. Age was significantly associated with survival to discharge, with older dogs less likely to survive than younger dogs. Duration of hospitalization was also associated with survival to discharge, with longer hospital stays associated with a lower likelihood of survival to discharge. Findings suggested that serum TT4 concentration at admission to an ICU had no prognostic value in this population of critically ill dogs.

Thyroid axis and adrenal activity in 28 day survivor and nonsurvivor dogs involved in recent road traffic accidents: A cohort study of 420 dogs

The objective of this retrospective cohort study was to determine the impact of a recent trauma on thyroid axis and adrenal activity in dogs and to assess the usefulness of urinary cortisol-to-creatinine ratio (UCCR), basal serum thyroid-stimulating hormone (TSH), total thyroxine (tT4), and free thyroxine (fT4) concentrations in predicting outcome in dogs traumatized by a road traffic accident (RTA).An RTA exposed group of 210 dogs was evaluated within 24 hours of the trauma. Their data were compared with data from a matched group of dogs with other diagnoses.UCCR was positively correlated with the trauma severity and was higher in the exposed group than in the nonexposed group (median 101.500 vs. 21.02; p < 0.0001). tT4 values were statistically similar between the two groups, but were correlated with a trauma score, while TSH (median = 0.050 vs. 0.080 ng/mL; p < 0.0001) and fT4 (median = 15.850 vs. 17.950 pmol/L; p = 0.0037) were significantly lower for the exposed group.Nonsurvivors in comparison to survivors presented and higher median UCCR (181.800 vs. 93.850 respectively; p = 0.020), and a lower serum fT4 (12.700 vs. 16.500 pmol/L, respectively; p = 0.0046). A similar pattern had been observed for tT4. TSH levels were not predictive of survival.This study provides insights into the endocrine characteristics of dogs suffering from acute trauma. UCCR was higher while fT4 and TSH were both lower in RTA-injured dogs than in dogs affected by other conditions. Furthermore low fT4 and tT4, and a high UCCR could be useful prognostic factors in dogs affected by RTA trauma.

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

BackgroundSerum 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.ObjectivesTo 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.AnimalsEighty client‐owned hyperthyroid cats.MethodsProspective 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.ResultsMean 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 importanceDiscordant 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.

A study on lipid profile in subclinical hypothyroidism of patients attending a tertiary care hospital

Subclinical hypothyroidism is also known as mild hypothyroidism, early thyroid failure, preclinical hypothyroidism and decreased thyroid reserve. Subclinical hypothyroidism is defined as a high serum thyroid-stimulating hormone concentration and normal serum total or free thyroxine and triiodothyronine concentrations associated with few or no symptoms and signs of hypothyroidism and thus subclinical hypothyroid disease is diagnosed by laboratory findings.Subclinical hypothyroidism is far more common than overt hypothyroidism. The prevalence of subclinical hypothyroidism is relatively high and ranges from 4%-8.5% and maybe as high as 20% in women older than 60years. Subclinical hypothyroidism is more common in elderly women than men. It is found twice as often in women as in men. Thyroid hormones have a known effect on heart rate &amp; cardiac excitability. Cardio vascular system is the major system affected by subclinical hypothyroidism. Subclinical hypothyroidism patients have an increased risk of “atherosclerosis” &amp; coronary artery disease. Subclinical hypothyroidism patients will have an increased level of total cholesterol, triglyceride, low-density lipoprotein and decreased level of high-density lipoprotein, leading to “atherosclerosis”. This study was conducted totally on 110 human subjects of age group 18-60 years. Among the 110 human subjects, 55 were Euthyroid controls and 55 were subclinical hypothyroid cases. Serum total cholesterol, serum triglycerides, serum low-density lipoproteins, levels were increased in subclinical hypothyroid cases than Euthyroid controls with a high statistical significance with the P-value &lt;0.001 and serum high-density lipoproteins levels are decreased in subclinical hypothyroid cases than Euthyroid controls with a high statistical significance with the P-value &lt;0.001. Hence, it should be made mandatory that the estimation of lipid profile should be made as a routine investigation in all cases of subclinical hypothyroidism.

Comparison of 2 assays for measuring serum total thyroxine concentration in dogs and cats.

BackgroundNo gold standard assay for serum total thyroxine (TT4) concentration in small animals exists. The Microgenics DRI TT4 (MTT4) assay is used by most reference laboratories.Hypothesis/ObjectivesIDEXX Catalyst Total T4 (CTT4) and Immulite 2000 TT4 (ITT4) results will agree with MTT4 results.AnimalsResidual small animal sera were randomized before reanalysis (dogs, CTT4 versus MTT4: n = 176, ITT4 versus MTT4: n = 74; cats, CTT4 versus MTT4: n = 319, ITT4 versus MTT4: n = 79).MethodsValidation and method comparison study. Serum TT4 concentration was measured on all analyzers. Pairwise Pearson correlation, cumulative sum linearity test, regression, and Bland‐Altman method were performed.ResultsCTT4 versus MTT4 in dogs: constant bias (y‐intercept) was 0.10 μg/dL (95% confidence interval [CI], 0.05‐0.15), proportional bias (slope) was 0.86 μg/dL (95% CI, 0.83‐0.89); in cats, constant bias was 0.13 μg/dL (95% CI, 0.08‐0.20) and proportional bias was 1.01 μg/dL (95% CI, 0.98‐1.03), but the test for linearity failed. Bland‐Altman plots identified increasing disagreement with increasing serum TT4 concentrations.ITT4 versus MTT4 in dogs, constant bias was 0.14 μg/dL (95% CI, 0.04‐0.22) and 0.22 μg/dL (95% CI, 0.09‐0.33) for cats; proportional bias was 0.76 (95% CI, 0.72‐0.80) for dogs and 0.71 (95% CI, 0.69‐0.74) for cats.Conclusions and Clinical ImportanceDifferences in CTT4 and MTT4 results affect interpretation at higher serum TT4 concentrations. The ITT4 proportional bias will underestimate serum TT4 concentrations in dogs and cats, compared to MTT4. Serial TT4 measurements should be done using the same assay.

Hyperthyroidism in cats: should we be routinely testing for early diagnosis?

Background: Routine testing for hyperthyroidism could become standard practice in all cats, before the onset of clinical signs. Aims: To describe serum total thyroxine (T4) concentration levels in a population of clinically normal cats; to determine the range of T4 levels in clinically normal cats; to estimate the prevalence of hyperthyroidism in clinically normal cats and to identify risk factors for elevated T4 levels in clinically normal cats tested for hyperthyroidism and are diagnosed. Methods: Total T4 records of 202 clinically normal cats, tested for routine pre-anaesthetic bloods, using a Quantum Saturno 100 Vet wet chemistry analyser, were analysed retrospectively. Any result above or below the normal reference range was classified as being hypo/hyperthyroid. Statistical Package for Social Sciences (SPSS) software assisted in the analysis of blood results and highlighted risk factors associated with the disease. Results: Out of the 202 clinically normal cats, 76 did, in fact, have hyperthyroidism. There was a statistically significant association between breed and T4 result, with a much higher prevalence of hyperthyroidism and higher median T4 result in purebreed cats compared with crossbreed cats. Thus providing evidence that routine testing on all purebreed cats could be worthwhile. Age, weight, gender, neutered status and colour were not significantly associated with hyperthyroidism or T4 result. Conclusion: Purebreed cats are a group that could be routinely tested for hyperthyroidism, as results showed a statistically significant association between breed and T4 result.

Prevalence of iatrogenic hypothyroidism in hyperthyroid cats treated with radioiodine using an individualised scoring system.

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. 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. 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. 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.

The relationships between blood lead levels and serum thyroid stimulating hormone and total thyroxine in the third National Health and Nutrition Examination Survey

Regression analysis was used to estimate and test for relationships between the blood lead concentration and the concentrations of serum thyroid stimulating hormone and serum total thyroxine in adults, 20 years and older, participating in the third National Health and Nutrition Examination Survey. No relationship was found between the blood lead level and the concentration of serum thyroid stimulating hormone. The serum total thyroxine concentration decreased as the blood lead level increased in women, but not in men. The lowest concentration of blood lead at which a relationship could be detected was 2.1 μg/dL and 3.9 μg/dL for the non-pregnant and pregnant women, respectively. Hypothetical mechanisms of the action of lead are discussed.

Serum Thyroid Hormone and Thyrotropin Concentrations in Adult Horses as They Age

With more horses remaining active longer in life, it is important to characterize changes that occur normally with aging, so that these can be differentiated from development of disease. The objective of the study was to test the hypotheses that geriatric horses have lower circulating concentrations of thyroid hormones and/or higher serum thyrotropin (TSH) concentrations compared to younger horses. Serum thyroid hormone and TSH concentrations from 71 normal, healthy horses that had participated in prior research projects were analyzed for effects of age, sex, and season when samples were obtained. All samples had been assayed in the same previously validated radioimmunoassays. There were no differences in serum concentrations of thyroid hormones or TSH by sex or season. Serum total thyroxine (T4) was greater in 3- to 6-year-old horses compared to all other age groups and was negatively correlated with age. There were no differences among age groups for free T4 and total and free tri-iodothyronine (T3). Serum TSH concentration was significantly greater in old horses (≥15 or ≥20 years) compared to young (3–10 years) and intermediate (11–14 years) age groups. Serum TSH was positively correlated with age. There were no significant differences in thyroid hormone responses to thyrotropin releasing hormone (TRH) among young, intermediate, or old horses. However, the TSH response to TRH was significantly different in both groups of older horses compared to intermediate and young horses. Serum total thyroxine concentrations decrease and serum TSH concentrations increase in horses as they age, with no changes in free T4 or T3.

Concurrent Milk Ingestion Decreases Absorption of Levothyroxine.

Levothyroxine is the most commonly prescribed medication in the United States. Many foods and medications, including calcium supplements, can interfere with levothyroxine absorption. No studies have investigated the effect of cow's milk, a common breakfast staple, on the absorption of oral levothyroxine. Cow's milk contains approximately 450 mg of elemental calcium per 12 oz (355 mL) serving. A pharmacokinetic study was conducted in healthy euthyroid subjects to assess levothyroxine absorption with and without concurrent cow's milk consumption. Following an overnight fast, serum total thyroxine (TT4) concentrations were measured at baseline and at one, two, four, and six hours after ingestion of 1000 μg of oral levothyroxine alone or when co-administered with 12 oz (355 mL) of 2% milk. There was a four-week washout period between the two assessments in each subject. Ten subjects (Mage ± SD = 33.7 ± 10.2 years; 60% male) completed the study. The area under the curve (AUC) of TT4 concentrations was significantly lower when levothyroxine was ingested along with 12 oz (355 mL) of 2% cow's milk (M ± SD = 67.3 ± 12.1) compared to that with levothyroxine alone (73.5 ± 17.0; p = 0.02). Also, peak serum TT4 concentrations were significantly lower when cow's milk was co-administered with levothyroxine (M ± SD = 14.1 ± 0.8 μg/dL) than with levothyroxine alone (13.0 ± 0.9 μg/dL; p = 0.04). This is the first study to demonstrate that concurrent cow's milk ingestion reduces oral levothyroxine absorption. The findings support previous literature showing the interference of elemental calcium and food with thyroid hormone absorption. Patients managed with thyroid hormone should be advised to avoid taking their levothyroxine simultaneously with cow's milk.

Clinical Consequences of Hypertriglyceridemia-Associated Proteinuria in Miniature Schnauzers.

BackgroundPrimary hypertriglyceridemia is a common condition in older Miniature Schnauzers that recently has been associated with proteinuria and underlying glomerular pathology, particularly glomerular lipid thromboemboli. Consequences of glomerular disease can include hypertension, thromboembolic disease, and cardiac disease. The incidence of these sequelae in Miniature Schnauzers with hypertriglyceridemia‐associated proteinuria (HTGP) is unknown.ObjectiveTo investigate prevalence of hypertension, decreased antithrombin III activity, and cardiac disease in Miniature Schnauzers with and without HTGP.AnimalsThirty‐two Miniature Schnauzers ≥7 years old.MethodsProspective case‐control study. Data collected from dogs included a CBC, biochemistry panel, urinalysis, urine protein‐to‐creatinine ratio, urine cortisol‐to‐creatinine ratio, serum total thyroxine concentration, fasting serum triglyceride concentration, indirect blood pressure, antithrombin III activity, and serum cardiac troponin I concentration. Results from dogs with HTGP (serum triglyceride concentration ≥ 100 mg/dL and urine protein‐to‐creatinine ratio >0.5) were statistically compared to normotriglyceridemic, nonproteinuric dogs.ResultsEighteen of the 32 dogs (56%) had primary hypertriglyceridemia. Of those dogs, 8 of 18 had proteinuria. None of the HTGP dogs were azotemic or hypoalbuminemic. Serum albumin concentration, alkaline phosphatase activity, and cholesterol concentration were significantly increased in dogs with HGTP compared to those without HGTP. No increased risk of hypertension, decreased antithrombin III activity, or cardiac disease was noted. Limited data from 8 dogs with HTGP showed no development of hypoalbuminemia or azotemia over a median follow‐up period of 18 months.Conclusions and Clinical ImportanceGeriatric Miniature Schnauzers with HGTP may have a good prognosis overall, and are not typically azotemic or hypoalbuminemic.

Evaluation of Gastric pH and Serum Gastrin Concentrations in Cats with Chronic Kidney Disease.

BackgroundChronic kidney disease (CKD) is a highly prevalent condition in cats. Advanced CKD is associated with hyporexia and vomiting, which typically are attributed to uremic toxins and gastric hyperacidity. However, gastric pH studies have not been performed in cats with CKD.Hypothesis/ObjectivesTo determine if cats with CKD have decreased gastric pH compared to age‐matched, healthy cats. Based on previous work demonstrating an association of hypergastrinemia and CKD, we hypothesized that cats with CKD would have decreased gastric pH compared to healthy, age‐matched control cats.Animals10 CKD cats; 9 healthy control cats.MethodsAll cats with concurrent disease were excluded on the basis of history, physical examination, CBC, plasma biochemistry profile, urinalysis, urine culture, serum total thyroxine concentration, and serum symmetric dimethylarginine concentration (controls only) obtained within 24 hours of pH monitoring and assessment of serum gastrin concentrations. Serum for gastrin determination was collected, and 12‐hour continuous gastric pH monitoring was performed in all cats. Serum gastrin concentration, mean pH, and percentage time that gastric pH was strongly acidic (pH <1 and <2) were compared between groups.ResultsNo significant differences in serum gastrin concentrations were observed between groups (medians [range]: CKD, 18.7 ng/dL [<10–659.0]; healthy, 54.6 ng/dL [<10–98.0]; P‐value = 0.713) or of any pH parameters including mean ± SD gastric pH (CKD, 1.8 ± 0.5; healthy, 1.6 ± 0.3; P‐value = 0.23).Conclusions and Clinical ImportanceThese findings suggest that cats with CKD may not have gastric hyperacidity compared to healthy cats and, therefore, may not need acid suppression. Thus, further studies to determine if there is a benefit to acid suppression in cats with CKD are warranted.

Survival times for cats with hyperthyroidism treated with a 3.35 mCi iodine-131 dose: a retrospective study of 96 cases.

Objectives Radioiodine (131I) dose determination using radiotracer kinetic studies or scoring systems, and fixed relatively high 131I dose (ie, 4 or 5 mCi) administration, are effective and associated with prolonged survival times for hyperthyroid cats. The latter method is less complicated but could expose patients and veterinary personnel to unnecessary levels of radiation. The aim of this study was to retrospectively evaluate the efficacy of a fixed 3.35 mCi 131I dose for the treatment of 96 hyperthyroid cats with no length estimation for any palpated goitre ⩾20 mm, assess outcome and identify factors associated with survival. Methods Serum total thyroxine concentrations at diagnosis and at follow-up times, survival times and cause of death were recorded. Multivariable Cox regression analysis was used to identify factors associated with time to any cause of death from 131I therapy initiation. Results Administration of a median (interquartile range) dose of 3.35 mCi (3.27-3.44 mCi) radioiodine was an effective treatment in 94/96 cats, but two cats remained hyperthyroid. No death related to hyperthyroidism was recorded. Median survival time was 3.0 years; the 1 and 2 year survival rates after 131I therapy were 90% and 78%, respectively. Low body weight (⩽3.1 kg; adjusted hazard ratio [aHR] 5.88; 95% confidence interval [CI] 2.22-16.67; P <0.01) and male gender (aHR 2.63; 95% CI 1.01-7.14; P = 0.04) were independently associated with death, whereas age, prior treatment with antithyroid drugs, reason for treatment and pretreatment azotaemia were not. Conclusions and relevance This study suggests that a fixed 3.35 mCi 131I dose treatment is effective for hyperthyroid cats with goitre(s) with a maximal length estimation <20 mm, that long-term survival can be achieved and that low body weight and male gender are significantly associated with shorter survival times.