Comparisons between cats with normal and increased fPLI concentrations in cats diagnosed with inflammatory bowel disease

Objectives : The aim of this study was to compare age, serum albumin and cobalamin concentrations, serum alanine amino transferase and alkaline phosphatase activities, feline inflammatory bowel disease clinical disease activity index, pancreatic ultrasound findings, intestinal histopathology scores, outcome, treatment and clinical response between cats diagnosed with inflammatory bowel disease with normal or increased serum feline pancreatic lipase immunoreactivity concentrations. Methods : Medical records for 23 cats diagnosed with inflammatory bowel disease and with serum feline pancreatic lipase immunoreactivity concentrations available were reviewed. Three groups were compared; cats with serum feline pancreatic lipase immunoreactivity concentrations 2·0 to 6·8 µg/l (group A), 6·9 to 11·9 µg/l (group B) and ≥12·0 µg/l (group C). Results : Sixteen of the 23 cats had increased serum feline pancreatic lipase immunoreactivity concentrations; 9 cats in group B and 7 cats in group C. The remaining seven cats were in group A. Cats with serum feline pancreatic lipase immunoreactivity concentrations ≥12·0 µg/l had significantly lower median serum albumin and cobalamin concentrations. No significant differences were identified between the three groups for age, serum alanine amino transferase and alkaline phosphatase activities, feline inflammatory bowel disease clinical disease activity index, pancreatic ultrasound findings, intestinal histopathology scores, clinical outcome, treatment or clinical response. Clinical Significance : Hypoalbuminaemia and hypocobalaminaemia were more frequently observed in cats with serum feline pancreatic lipase immunoreactivity concentrations ≥12·0 µg/l.     

Use of the Thyrotropin Releasing Hormone Stimulation Test to Diagnose Mild Hyperthyroidism in Cats

We evaluated serum T₄ and T₃ concentrations before and after administration of thyrotropin releasing hormone (TRH) in 35 cats with mild to moderate hyperthyroidism. 15 cats with nonthyroidal disease, and 31 clinically normal cats. The TRH stimulation test was performed by collecting blood for serum T₄ and T₃ determinations before and 4 hours after IV administration of 0.1 mg/kg TRH. Mean basal serum thyroid hormone concentrations in hyperthy-roid cats were significantly (P < .05) higher than concentrations in normal cats and in those with nonthyroidal disease, but there was considerable overlap among the 3 groups. After administration of TRH, mean serum T₄ concentrations increased significantly in all groups of cats, whereas mean T₃ concentrations increased significantly in normal cats and in those with nonthyroidal disease, but not in cats with hyperthyroidism. The absolute difference between mean basal and TRH-stimulated serum concentrations of T₄ in cats with hyperthyroidism (10.7 nmol/L) was significantly lower than the difference in the cats with nonthyroidal disease (20.0 nmol/L) and in clinically normal cats (28.3 nmol/L), but there was considerable overlap in values among groups. The mean value for relative change in serum T₄ concentration after TRH was significantly lower incats with hyperthyroidism (18.9%) than in those with nonthyroidal disease (110.0%) and in clinically normal cats (130.2%). Serum T₄ concentrations increased by > 50% in all normal cats and cats with nonthyroidal disease, whereas only 4(11.4%) of the 35 hyperthyroid cats had an increase of > 50% after TRH administration. On the basis of canonical discriminate analysis, the mean discriminant function score was significantly higher in the hyperthyroid cats (D = 63.8) than in cats with nonthyroidal disease (D = 5.9) or clinically normal cats (D = 0.7). All cats having a discriminant function score > 30 were hyperthyroid, whereas all cats with a value < 20 were euthyroid. Adverse side effects associated with administration of TRH were common and included transient vomiting, salivation, tachypnea, and defecation. Results of this study indicate that the TRH stimulation test is a useful aid in the diagnosis of hyperthyroidism in cats when basal serum T₄ concentrations are high-normal or only slightly high. As a diagnostic test, the TRH stimulation test compares favorably with the T₃ suppression test but requires less time and is more convenient to perform.     

Relationships between Low Serum Cobalamin Concentrations and Methlymalonic Acidemia in Cats

Background: Serum cobalamin concentrations below reference range are a common consequence of gastrointestinal disease in cats. Serum cobalamin ≤ 100 ng/L is associated with methylmalonic acidemia.
Objectives: To determine the prevalence of cobalamin deficiency, defined by elevated serum methylmalonic acid (MMA), in cats with serum cobalamin ≤ 290 ng/L, and the optimum serum cobalamin concentration to predict cobalamin deficiency in cats.
Sample Set: Residual serum samples (n = 206) from cats with serum cobalamin ≤ 290 ng/L.
Methods: Retrospective, observational study. Serum cobalamin and folate were measured with automated assays. Serum MMA was determined by gas chromatography-mass spectrometry. Cobalamin deficiency was defined as serum MMA > 867 nmol/L. Sensitivity and specificity of serum cobalamin concentrations ≤290 ng/L for detecting MMA > 867 nmol/L were analyzed using a receiver-operator characteristic curve.
Results: There was a negative correlation between serum cobalamin and MMA concentrations (Spearman's r =−0.74, P < 0.0001). The prevalence of MMA ≥ 867 nmol/L in cats with serum cobalamin ≤ 290 ng/L was 68.4%. Serum cobalamin ≤ 160 ng/L had a 74% sensitivity and 80% specificity for detecting MMA > 867 nmol/L. No significant difference in serum folate concentrations was detected between affected and unaffected cats.
Conclusions and Clinical Importance: Elevated MMA concentrations, suggesting cobalamin deficiency, are common in cats with serum cobalamin ≤ 290 ng/L. Cobalamin deficiency is clinically significant, and supplementation with parenteral cobalamin is recommended for cats with gastrointestinal disease and low serum cobalamin concentrations.     

Evaluation of Serum Thyroid‐Stimulating Hormone Concentration as a Diagnostic Test for Hyperthyroidism in Cats

Background

In humans, measurement of serum thyroid‐stimulating hormone (TSH) concentration is commonly used as a first‐line discriminatory test of thyroid function. Recent reports indicate that canine TSH (cTSH) assays can be used to measure feline TSH and results can help diagnose or exclude hyperthyroidism.

Objectives

To investigate the usefulness of cTSH measurements as a diagnostic test for cats with hyperthyroidism.

Animals

Nine hundred and seventeen cats with untreated hyperthyroidism, 32 euthyroid cats suspected of having hyperthyroidism, and 131 clinically normal cats.

Methods

Prospective study. Cats referred to the Animal Endocrine Clinic for suspected hyperthyroidism were evaluated with serum T₄, T₃, free T₄ (fT ₄), and TSH concentrations. Thyroid scintigraphy was used as the gold standard to confirm or exclude hyperthyroidism.

Results

Median serum TSH concentration in the hyperthyroid cats (<0.03 ng/mL) was significantly (P < .001) lower than concentrations in clinically normal cats (0.05 ng/mL) or euthyroid cats with suspected thyroid disease (0.06 ng/mL). Only 18 (2.0%) hyperthyroid cats had measurable TSH concentrations (≥0.03 ng/mL), whereas 114 (69.9%) of the 163 euthyroid cats had detectable concentrations. Combining serum TSH with T₄ or fT ₄ concentrations lowered the test sensitivity of TSH from 98.0 to 97.0%, but markedly increased overall test specificity (from 69.9 to 98.8%).

Conclusions and Clinical Importance

Serum TSH concentrations are suppressed in 98% of hyperthyroid cats, but concentrations are measurable in a few cats with mild‐to‐moderate hyperthyroidism. Measurement of serum TSH represents a highly sensitive but poorly specific test for diagnosis of hyperthyroidism and is best measured in combination with T₄ and fT ₄.     

Radioactive iodine therapy for feline hyperthyroidism: Efficacy and administration routes

The efficacy of radioactive iodine (¹³¹I) administration was studied in a series of 50 hyperthy-roid cats. The dose administered to each cat was based on the clinical severity of the thyrotoxicosis, the serum total thyroxine (TJ concentration and the size of the goitre estimated by palpation. The activity ranged from 80 to 200 MBq (mean ± SD, 143 ± 24 MBq}. The ¹³¹I was injected intravenously in 27 cases and subcutaneously in 23 cases. Each cat was hospitalised for 30 days after the injection. Regardless of the route of injection, none of the cats exhibited any side effects after therapy and all tolerated the hospitalisation period well. There was a significant (P<0.001) decrease in the serum total T₄ concentration (reference range, 10.4 to 42.0 nmol/litre) from a mean ± SD of 181.3 ± 111.4 nmol/litre (range, 43.8 to 575.6 nmol/litre) to a mean ± SD of 19.0 ± 29.6 nmol/litre (range, 2.0 to 175.7 nmol/litre) 30 days following the injection of the radioisotope. Five cats remained hyperthyroid, although in each case the serum total T₄ concentrations had decreased from pre-treatment values. Two of the cats subsequently became euthyroid within three and five months of therapy, respectively, two were lost to adequate follow-up and the remaining cat was successfully retreated four months later. Before treatment, four of these cases had high scores based on the three criteria used for dose estimation. Serum total T₄ concentrations below the reference range developed after treatment in many cases, but were often transient. Clinical evidence of hypothyroidism was not apparent in any cat. Recurrence of hyperthyroidism has not occurred in follow-up periods of up to 32 months. There was no difference in the outcome between the cats injected intravenously or subcutaneously and the latter was considered to be safer and simpler. The administration of an approximated dose of ¹³¹I proved to be an effective treatment for hyperthyroidism in 47 (94.0 per cent) of the cats and obviated the need for sophisticated nuclear computer facilities. There may be a lag period in some cases before euthy-roidism is achieved and this should be considered before the administration of a second dose. ¹³¹I can be administered subcutaneously without untoward effects.     

Metabolism of amino acids in cats with severe cobalamin deficiency.

OBJECTIVE: To validate an automated chemiluminescent immunoassay for measuring serum cobalamin concentration in cats, to establish and validate gas chromatography-mass spectrometry techniques for use in quantification of methylmalonic acid, homocysteine, cysteine, cystathionine, and methionine in sera from cats, and to investigate serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine as indicators of biochemical abnormalities accompanying severe cobalamin (vitamin B12) deficiency in cats. SAMPLE POPULATION: Serum samples of 40 cats with severe cobalamin deficiency (serum cobalamin concentration < 100 ng/L) and 24 control cats with serum cobalamin concentration within the reference range. PROCEDURE: Serum concentrations of cobalamin were measured, using a commercial automated chemiluminescent immunoassay. Serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine were measured, using gas chromatography-mass spectrometry, selected ion monitoring, stable-isotope dilution assays. RESULTS: Cats with cobalamin deficiency had significant increases in mean serum concentrations bf methylmalonic acid (9,607 nmol/L), compared with healthy cats (448 nmol/L). Affected cats also had substantial disturbances in amino acid metabolism, compared with healthy cats, with significantly increased serum concentrations of methionine (133.8 vs 101.1 micromol/L) and significantly decreased serum concentrations of cystathionine (449.6 vs 573.2 nmol/L) and cysteine (142.3 vs 163.9 micromol/L). There was not a significant difference in serum concentrations of homocysteine between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cats with gastrointestinal tract disease may have abnormalities in amino acid metabolism consistent with cobalamin deficiency. Parenteral administration of cobalamin may be necessary to correct these biochemical abnormalities.     

Triiodothyronine (T3) suppression test. An aid in the diagnosis of mild hyperthyroidism in cats

The purpose of this study was to develop a T3 suppression test to help in the diagnosis of mild hyperthyroidism in cats. We evaluated the response in circulating T4 concentrations to exogenous T3 (liothyronine) administration in 44 clinically normal cats, 77 cats with hyperthyroidism, and 22 cats with nonthyroidal disease. The test was performed by first collecting blood samples for basal serum T4 and T3 determinations, administering liothyronine at an oral dosage of 25 micrograms three times daily for seven doses, and, on the morning of the third day, again collecting serum samples for T4 and T3 determinations 2 to 4 hours after the seventh dose of liothyronine. The mean basal serum concentrations of T4 (53.1 nmol/L) and T3 (1.8 nmol/L) were significantly higher in the cats with hyperthyroidism than in the normal cats (T4 = 25.3 nmol/L, T3 = 1.3 nmol/L) and the cats with nonthyroidal disease (T4 = 29.5 nmol/L, T3 = 1.4 nmol/L); however, there was a great deal of overlap of basal values between the three groups of cats. Of the 77 cats with mild hyperthyroidism, 41 (53%) had serum T4 values and 55 (71%) had T3 values that were within the established normal ranges. After administration of liothyronine, mean serum T4 concentrations fell much more markedly in the normal cats and the cats with nonthyroidal disease than in the hyperthyroid cats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum cobalamin concentrations in healthy cats and cats with non-alimentary tract illness in Australia

Objective   To determine a reference range for serum cobalamin concentration in healthy cats in Australia using a chemiluminescent enzyme immunoassay and to prospectively investigate the prevalence of hypocobalaminaemia in cats with non-alimentary tract disease.
Design   Prospective study measuring serum cobalamin concentrations in clinically healthy cats and cats with non-alimentary tract illness.
Procedure   Blood was collected from 50 clinically healthy cats that were owned by staff and associates of Veterinary Specialist Services or were owned animals presented to Creek Road Cat Clinic for routine vaccination. Blood was collected from 47 cats with non-alimentary tract illness presented at either clinic. Serum cobalamin concentration was determined for each group using a chemiluminescent enzyme immunoassay.
Results   A reference range for Australian cats calculated using the central 95th percentile in the 50 clinically healthy cats was 345 to 3668 pg/mL. Median serum cobalamin concentration in 47 cats with non-alimentary tract illness (1186 pg/mL; range 117–3480) was not significantly different to the median serum cobalamin of the 50 healthy cats (1213 pg/mL, range 311–3688). Using the calculated reference range one sick cat with non-alimentary tract illness had a markedly low serum cobalamin concentration.
Conclusion   Although hypocobalaminaemia is uncommon in sick cats with non-alimentary tract illness in Australia, its occurrence in this study warrants further investigation.     

Serum fructosamine concentration in cats with overt hyperthyroidism.

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

Carbimazole therapy of feline hyperthyroidism

The efficacy and safety of carbimazole (CBZ) was studied in a series of 45 hyperthyroid cats. CBZ was used before surgical thyroidectomy in 34 cats, at a dose of 5 mg administered orally every eight hours. Biochemical euthyroidism, as assessed by a decrease in serum total thyroxine (T₄) concentrations into the reference range, was achieved in 31 cats (91 per cent) within a mean (± SD) of 5–7 (± 2–9) days (range, three to 15 days). Clinical evidence of euthyroidism tended to lag behind biochemical evidence but was usually apparent after 14 days. Continuing therapy tended to decrease serum total T₄ but not serum total triiodothyronine (T₃) concentrations below the reference range but clinical evidence of hypothyroidism was not apparent. In five additional cats, 5 mg CBZ was administered three times between 08.00 and 20.00 hours. Euthyroidism was achieved in only one cat after 14 days, emphasising the need for eight hourly dosing. Clinically observable side effects developed in five cats (13 per cent), two to three weeks after commencing therapy and included vomiting (n y 2) and vomiting and anorexia (n = 3). In three cases withdrawal of CBZ was required. Mild and transient haematological abnormalities developed in two cats (one case each of lymphocytosis and leucopenia). There were significant decreases in serum concentrations of alanine aminotransferase and alkaline phosphatase in those cats achieving euthyroidism (P < 0–001 in each case) but not in those that remained hyperthyroid despite CBZ therapy (P ± 0–05 in each case). CBZ was used as the sole therapy for the condition in eight cats for between four and 65 weeks. A consistent dosage of 5 mg CBZ administered twice daily was necessary to maintain euthyroidism. Adverse reactions were not noted. Chronic medical management tended to depress serum total T₄ concentrations below the reference range. Corresponding serum total T₃ concentrations remained within the reference range on 15 (88 per cent) of 17 occasions and may explain why the animals appeared clinically euthyroid. CBZ appears to be a safe and effective drug both in the short and long term management of feline hyperthyroidism and can be recommended as the current drug of choice in the UK.     

Early biochemical and clinical responses to cobalamin supplementation in cats with signs of gastrointestinal disease and severe hypocobalaminemia

Domestic cats with small intestinal disease may develop cobalamin deficiency because of reduced small intestinal uptake of this vitamin. This study assessed the impact of cobalamin deficiency on biochemical and clinical findings in cats with intestinal disease. Nineteen pet cats, all with severe hypocobalaminemia (< or =100 ng/L) and histories of gastrointestinal signs, were studied. Cats received cobalamin, 250 microg SC once weekly, for 4 weeks. Biochemical indices of cobalamin availability (e.g., serum methylmalonic acid, homocysteine, and cysteine concentrations), serum feline trypsinlike immunoreactivity (fTLI) and serum folate concentrations, and clinical findings were recorded at the start of the study and after 4 weeks of cobalamin therapy. Serum methylmalonic acid (MMA) concentrations (median; range) decreased after cobalamin supplementation (5373.0; 708.5-29,329.0 versus 423.5; 214.0-7219.0 nmol/L, P < .0001). Serum homocysteine concentrations were not significantly altered (mean +/- SD 8.2 +/- 2.9 versus 10.3 +/- 4.5 micromol/L, P = .1198), whereas cysteine concentrations increased significantly (122.3 +/- 38.8 versus 191.5 +/- 29.4 micromol/L, P < .0001). Mean body weight increased significantly after cobalamin therapy (3.8 +/- 1.1 versus 4.1 +/- 1 kg, P < .01), and the average body weight gain was 8.2%. Significant linear relationships were observed between alterations in serum MMA and fTLI concentrations and the percentage body weight change (P < .05 for both, Pearson r2 = 0.26 and 0.245, respectively). Mean serum folate concentration decreased significantly (mean +/- SD 19 +/- 5 microg/L versus 15.4 +/- 6.2 microg/L, P < .001). Reduced vomiting and diarrhea were observed in 7 of 9 and 5 of 13 cats, respectively. These results suggest that cobalamin supplementation in cats with small intestinal disease and severe hypocobalaminemia is associated with normalization of biochemical test results and improvements in clinical findings in most affected cats.     

EVALUATION OF QUANTITATIVE THYROID SCINTIGRAPHY FOR DIAGNOSIS AND STAGING OF DISEASE SEVERITY IN CATS WITH HYPERTHYROIDISM: COMPARISON OF THE PERCENT THYROIDAL UPTAKE OF PERTECHNETATE TO THYROID‐TO‐SALIVARY RATIO AND THYROID‐TO‐BACKGROUND RATIOS

Thyroid scintigraphy is commonly used for evaluation of cats with hyperthyroidism, with the thyroid‐to‐salivary ratio (T/S) being the most common method to quantify the degree of thyroid activity and disease. Calculation of thyroid‐to‐background ratios (T/B) or percent thyroidal uptake of ^99mTcO^?₄ (TcTU) has only been reported in a few studies. The purpose of this prospective, cross‐sectional study was to evaluate a number of quantitative scintigraphic indices as diagnostic tests for hyperthyroidism, including the T/S, three different T/B, TcTU, and estimated thyroid volume. Of 524 cats referred to our clinic for evaluation of suspected hyperthyroidism, the diagnosis was confirmed (n = 504) or excluded (n = 20) based on results of a serum thyroid panel consisting of thyroxine (T₄), triiodothyronine (T₃), free T₄ (fT₄), and thyroid‐stimulating hormone (TSH) concentrations. In the hyperthyroid cats, median values for TcTU, T/S, and three T/B ratios were all significantly higher (P < 0.001) than values in euthyroid suspect cats or clinically normal cats. All scintigraphic parameters were relatively sensitive and specific as diagnostic tests for hyperthyroidism, but the T/S ratio had the highest test accuracy. The T/S ratio correlated strongly with the TcTU (r = 0.85). However, the TcTU had a higher and more significant correlation (P < 0.01) with serum T₄ (r = 0.76 vs. 0.64), T₃ (r = 0.77 vs. 0.64), and estimated thyroid volume (r = 0.62 vs. 0.38). Overall, calculation of TcTU is an accurate diagnostic test, but also appears to be the best parameter to predict the functional volume and metabolic activity of the feline adenomatous thyroid gland.     

Treatment of feline hyperthyroidism with radioactive iodine-131

Feline hyperthyroidism can be treated by thyroidectomy, antithyroid drugs, or radioactive iodine-131 (131I). The aim of this retrospective study was to evaluate the treatment of 83 hyperthyroid cats with 131I The dosage of 131I ranged from 4 to 6 milliCurie (mCi). Blood samples for determination of plasma concentrations of total thyroxine (TT4), urea, and creatinine were collected before, ten days after, and several months after treatment. In addition, arterial blood pressure was measured before and ten days after treatment. The median plasma TT4 concentration ten days after 131I treatment (27 nmol/L, 64 cats) was significantly lower than that before treatment (123 nmol/L). The median plasma TT4 concentration several months after 131I treatment was 22,5 nmol/L (40 cats). Ten days and several months after 131I treatment, plasma TT4 concentration had decreased below the upper limit of the reference range in 64 (77%) and 72 cats (87%), respectively. In four cats the plasma TT4 concentration had decreased below the lower limit of the reference range, but only two cats had symptoms of hypothyroidism. Plasma urea and creatinine concentrations were not increased ten days after 131I treatment, but the median plasma creatinine concentration was significantly higher several months after treatment when compared with before 131I treatment. Before treatment in 28 cats a high arterial blood pressure (> 180 mmHg) was measured, whereas after treatment in 25 cats a high arterial blood pressure was measured. The results of this study indicate that 131I treatment is an effective therapy in most cats with hyperthyroidism.     

Serum cobalamin concentrations in cats with gastrointestinal signs: correlation with histopathological findings and duration of clinical signs

The aims of this study were to investigate the prevalence of hypocobalaminaemia in UK cats presented for referral investigation of gastrointestinal signs and to ascertain whether the duration of clinical signs or severity of disease (based on WSAVA Gastrointestinal Standardization histopathological grading) related to cobalamin concentration. The study population comprised 39 cats, of which 11 (28.2%) had hypocobalaminaemia. Eight of these cats were diagnosed with a single cause of gastrointestinal signs: intestinal inflammation (five); alimentary lymphoma (two); and cholangitis (one). Two or more concurrent diseases were diagnosed in the three remaining cases. Alimentary lymphoma and the most severe grade of histological intestinal inflammation were associated most commonly with concurrent hypocobalaminaemia, but there was no statistically significant correlation between serum cobalamin concentrations and histopathological score or duration of clinical signs.     

Transdermal methimazole treatment in cats with hyperthyroidism

The objectives of this study were to assess serum thyroxine concentrations and clinical response in hyperthyroid cats to treatment with transdermal methimazole, and to determine if further investigation is indicated.Clinical and laboratory data from 13 cats with hyperthyroidism were retrospectively evaluated. Methimazole (Tapazole, Eli Lilly) was formulated in a pleuronic lecithin organogel (PLO)-based vehicle and was applied to the inner pinna of the ear at a dosage ranging from 2.5mg/cat q 24h to 10.0mg/cat q 12h. During the treatment period, cats were re-evaluated at a mean of 4.3 weeks (recheck-1), and again at a mean of 5.4 months (recheck-2).Clinical improvement was observed, and significant decreases in thyroxine concentrations were measured at recheck-1 (mean: 39.57nmol/L, SEM: 14.4, SD: 41.2) and recheck-2 (mean: 36.71nmol/L, SEM: 13.9, SD: 45.56) compared to pretreatment concentrations (mean: 97.5nmol/L, SEM: 11.42, SD: 39.5). No adverse effects were reported.     

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

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

Effect of clomipramine on the electrocardiogram and serum thyroid concentrations of healthy cats

Clomipramine is a tricyclic antidepressant (TCA) commonly used to treat anxiety related behavioral disorders in companion animals. Tricyclic antidepressants (TCAs) have the potential to cause arrhythmias in humans and companion animals. The effect of the TCAs, clomipramine, and amitriptyline, at therapeutic dosages on cardiac rhythm has been evaluated in dogs. The effect of clomipramine on the cardiac rhythm of cats has not been reported. In Experiment 1, 7 healthy cats were selected to evaluate the effect of clomipramine on their cardiac rhythm using an electrocardiogram. A baseline electrocardiogram was carried out before (Day 0) and repeated (Day 29) after 4 weeks (28 days) of daily clomipramine (10 mg/cat PO) administration. Significant changes in the electrocardiogram were not found after 28 days of daily clomipramine administration. In Experiment 2, 7 healthy cats were enrolled in the study to evaluate the effect of clomipramine administration on the serum thyroid concentrations in cats. Clomipramine (10 mg/cat PO daily) was administered to all cats beginning on Day 1, and continued for 28 days. Serum total thyroxine (T₄), triiodothyronine (T₃), and free thyroxine (fT₄) concentrations were measured before (Day 0) and repeated (Day 29) after 4 weeks (28 days) of daily clomipramine administration. Statistically significant decreases in serum thyroid concentrations (T_4, T₃, and fT₄) were noted between pre and post clomipramine administration. A decrease of 25, 24, and 16% in serum T₄, T₃, and fT₄ concentrations, respectively, may lead to a misdiagnosis of euthyroidism in a subclinical hyperthyroid patient. A longer duration of drug treatment might further suppress thyroid function when used as a single agent, with concomitantly administered drugs, or in conjunction with euthyroid sick syndrome.     

ULTRASONOGRAPHIC EXAMINATION OF THE THYROID GLAND OF HYPERTHYROID CATS: COMPARISON TO 99mTcO−4 SCINTIGRAPHY

High-resolution ultrasonography was evaluated as an alternative to ^99mTcO^-₄ scintigraphy for examining size and appearance of thyroid glands in hyperthyroid cats. Thyroid ultrasound examinations were performed on 6 normal cats and 14 cats with hyperthyroidism. Thyroid lobe volume was estimated from ultrasound images using the equation for a prolate ellipsoid, π/6 (length * height * width). Total thyroid volume was estimated by adding the volume estimations of the left and right lobes. Thyroid lobes of hyperthyroid cats were considered abnormal if estimated volume exceeded the 99% confidence interval for normal thyroid volume determined from the control group. Scintigraphic examinations performed on hyperthyroid cats were evaluated for unilateral versus bilateral disease and for the presence of ectopic activity. Mean thyroid lobe volume and total thyroid volume for normal cats was 85 and 169 mm³, respectively. Mean thyroid lobe volume and total thyroid volume for hyperthyroid cats was 578 and 889 mm³. There was a significant difference in mean estimated total thyroid volume of normal and hyperthyroid cats. Thyroid lobes with greater than normal TcO^-₄ uptake on scintigraphy were larger and had variable homogeneity, echogenicity, and margination on ultrasound examination. There also was an 85.7% agreement of scintigraphy and ultrasonography in differentiating normal from abnormal thyroid lobes. A fair correlation between estimated total thyroid volume of hyperthyroid cats and most recent pretherapy serum thyroxine values were also found. This preliminary study indicates that thyroid ultrasound examination may provide information that is useful for diagnosis and treatment of feline hyperthyroidism. Although ultrasound provides accurate evaluation of the thyroid glands, it cannot replace ^99mTcO^-₄ scintigraphy for screening of metastatic lesions and ectopic glands.     

Effect of grazing pasture with a low selenium content on the concentrations of triiodothyronine and thyroxine in serum,and GSH-Px activity in erythrocytes in cows in Chile

AIM: To determine the effect of grazing pasture that had a low selenium (Se) concentration on serum concentrations of tri iodothyronine (T₃) and thyroxine (T₄), and erythrocyte glutathione peroxidase (GSH-Px) activity in dairy cows.

METHODS: Forty pregnant Friesian cows were grazed on pasture that contained 0.03–0.04 ppm Se on a dry matter (DM) basis. Two months before parturition, 20 cows were randomly selected and treated with 1 mg Se/kg bodyweight subcutaneously, as barium selenate (Group Se-S). The other group (Se-D) was not supplemented. Blood samples were taken before supplementation (-60 days) and 30, 60, 90, 180 and 270 days after parturition, for determination of concentrations of T₃ and T₄ in serum, and GSH-Px activity in erythrocytes.

RESULTS: Erythrocyte GSH-Px activity in the Se-D group was >60 U/g haemoglobin (Hb) throughout the experiment. Supplementation increased (p>0.05) activities to >130 U/g Hb throughout lactation. Mean serum concentrations of T₄ in Se-D and Se-S cows increased from 23.7 (SEM 0.7) and 23.4 (SEM 0.8) nmol/L, respectively, in the prepartum period to 69.6 (SEM 0.1) and 67.6 (SEM 0.2) nmol/L, respectively, at 180 days of lactation (p>0.01), and no effect of Se supplementation was evident. Serum concentrations of T₃ in Se-D cows decreased (p>0.05) from 1.6 (SEM 0.1) nmol/L prepartum to 1.0 (SEM 0.2) nmol/L at the beginning of lactation, and remained lower (p>0.05) than those in the Se-S cows which did not decrease after calving and ranged from 1.9 (SEM 0.1) to 2.4 (SEM 0.2) nmol/L throughout lactation.

CONCLUSIONS: Serum T₃ concentrations decreased during early lactation in unsupplemented cows grazing pastures low in Se (0.03–0.04 ppm) and both serum T₃ and erythrocyte GSH-Px activities were consistently lower throughout lactation compared with Se-supplemented cows. Se supplementation had no effect on serum T₄ concentrations.     

Serum cobalamin concentrations in dogs with leishmaniosis before and during treatment

Hypocobalaminemia in dogs is most commonly associated with gastrointestinal disorders leading to impaired absorption and utilization of cobalamin. The objectives of this study were to compare serum cobalamin concentrations between dogs with leishmaniosis and clinically healthy dogs, and to assess possible alterations of serum cobalamin concentrations in dogs with leishmaniosis at different timepoints during treatment. Fifty-five dogs with leishmaniosis and 129 clinically healthy dogs were prospectively enrolled. Diagnosis of leishmaniosis was based on clinical presentation, positive serology and microscopic detection of Leishmania amastigotes in lymph node aspiration smears. Twenty of the dogs with leishmaniosis were treated with a combination of meglumine antimonate and allopurinol for 28 days and serum cobalamin concentrations were measured in blood samples that were collected before initiation of treatment (timepoint 0) and on days 14 and 28. In order to estimate alterations of serum cobalamin concentrations during treatment, cobalamin concentrations were measured in blood samples from 20 out of 55 dogs with leishmaniosis at all timepoints. Serum cobalamin concentrations were significantly lower in dogs with leishmaniosis before treatment (median: 362 ng/L; IQR: 277−477 ng/L) compared to clinically healthy dogs (median: 470 ng/L; IQR: 367−632 ng/L; P = 0.0035). Serum cobalamin concentrations increased significantly in dogs with leishmaniosis on day 14 of treatment compared to timepoint 0 (P = 0.02).In the present study, serum cobalamin concentrations were significantly lower in dogs with leishmaniosis compared to clinically healthy dogs. In addition, there was an increase in serum cobalamin concentrations during treatment. The clinical significance of hypocobalaminemia in dogs with leishmaniosis remains to be determined.