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Summary

Echocardiograms and ecg were obtained for 11 hypothyroid dogs before and after levothyroxine supplementation (0.022 mg/kg of body weight, q 12 h for 64 ± 12 days). Evidence of impaired left ventricular function was found in the dogs before treatment. A significant decrease in shortening fraction and velocity of circumferential fiber shortening, increase in left ventricular end-systolic diameter, and prolongation of preejection period was noted when comparing measurements before and after levothyroxine supplementation. Amplitude of the P and R waves was significantly higher after treatment than before. It was concluded that changes in cardiac function can be reversed in hypothyroid dogs.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Sixty-six dogs with hypothyroidism were identified from dogs examined over a 5-year period. Hypothyroidism was diagnosed only if the dog had a low, resting serum thyroxine concentration and serum thyroxine concentration was not higher than the lower limits of the reference range 6 hours after iv administration of bovine thyrotropin.

The prevalence of hypothyroidism was 0.2%. Neutering was determined to be the most significant gender-associated risk factor for development of hypothyroidism. Neutered male and spayed female dogs had a higher relative risk of developing hypothyroidism than did sexually intact females. Sexually intact females had a lower relative risk. Breeds with a significantly increased risk, compared with other breeds, were the Doberman Pinscher and Golden Retriever. The most common clinical findings were obesity (41%), seborrhea (39%), alopecia (26%), weakness (21%), lethargy (20%), bradycardia (14%), and pyoderma (11 %). Low voltage R-waves were found, on 58% of ecg. Clinicopathologic abnormalities included hypercholesterolemia (73%), nonregenerative anemia (32%), high serum alkaline phosphatase activity (30%), and high serum creatine kinase activity (18%). Serum total triiodothyronine concentrations were within reference ranges in 15% of the hypothyroid dogs. Response to treatment was good in most dogs, but those with severe concurrent disease or neurologic abnormalities were less likely to respond with complete resolution of clinical signs.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effects of etodolac administration on results of thyroid function tests and concentrations of plasma proteins in clinically normal dogs.

Animals—19 healthy random-source mixed-breed dogs.

Procedure—Blood samples for measurement of serum thyroxine (T4), 3,5,3'-triiodothyronine (T3), free T4 (fT4), and endogenous canine thyroid stimulating hormone (cTSH) were measured twice before as well as on days 14 and 28 of etodolac administration (mean dosage, 13.7 mg/kg, PO, q 24 h). Plasma total protein, albumin, and globulin concentrations and serum osmolality were measured once before as well as on days 14 and 28 of etodolac administration.

Results—Etodolac administration did not significantly affect serum T4, T3, fT4, or cTSH concentrations or serum osmolality. Significant decreases in plasma total protein, albumin, and globulin concentrations were detected on days 14 and 28 of administration.

Conclusions and Clinical Relevance—Results of thyroid function tests are not altered when etodolac is administered for up to 4 weeks. Therefore, interpretation of results of these tests should accurately reflect thyroid function during etodolac treatment. Plasma total protein, albumin, or globulin concentrations that are less than the respective reference range in a dog administered etodolac for ≥ 2 weeks may be an effect of treatment rather than an unrelated disease process. A decrease in plasma protein concentrations may reflect subclinical injury of the gastrointestinal tract. (Am J Vet Res 2002;63:1492–1495)

Full access
in American Journal of Veterinary Research

Summary

Plasma von Willebrand factor antigen concentration was measured in 10 dogs with hypothyroidism, before and after administration of a replacement dose of levothyroxine for 67 ± 12 days. Results were reported as a percentage of normal activity, with plasma pooled from clinically normal dogs given a value of 100%. Plasma von Willebrand factor antigen concentration was within reference limits in dogs with hypothyroidism (126 ± 41%) and was significantly (P < 0.01) decreased (94 ± 39%) after treatment with levothyroxine. Contrary to findings in some other studies, a deficiency of plasma von Willebrand factor did not appear to result from hypothyroidism.

Free access
in Journal of the American Veterinary Medical Association

Objective—

To characterize the frequency, medical history, clinical signs, methods of treatment, and outcome of insulin-induced hypoglycemia and to identify predisposing factors.

Design—

Retrospective study.

Animals—

8 dogs and 20 cats with diabetes mellitus that developed hypoglycemia because of insulin overdose.

Procedure—

Medical records of dogs and cats receiving insulin for treatment of diabetes mellitus were reviewed. Medical records of dogs and cats that had an episode of hypoglycemia were reviewed in detail.

Results—

Overdosing of insulin was more common in cats than in dogs. Median weight of diabetic cats that became hypoglycemic was significantly greater than that of the hospital population of diabetic cats at diagnosis. Eighty percent of cats that became hypoglycemic were receiving insulin doses > 6 U/injection, administered once or twice daily. Dose and type of insulin did not correlate with duration or severity of hypoglycemia. In 7 of 8 dogs and 10 of 20 cats, management factors or concurrent medical problems were considered to be predisposing causes for insulin overdose. Two dogs and 2 cats did not have clinical signs of hypoglycemia, despite documented low concentrations of glucose in their blood.

Clinical Implications—

Diabetic cats, especially if obese, are at greater risk of insulin overdose than are diabetic dogs. The reason for overdose may not be evident. Diabetic dogs and cats may become hypoglycemic without developing autonomic warning signs of hypoglycemia, or these signs may not be recognized (hypoglycemia unawareness). (J Am Vet Med Assoc 1997;211:326–330)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objectives—To measure urine concentrations of sulfated glycosaminoglycans (GAGs), determine optimal storage conditions for urine samples, establish a reference range, and determine whether there is correlation between 24-hour total urine GAG excretion and the GAG-to-creatinine ratio (GCR).

Animals—14 healthy adult dogs.

Procedure—Single urine sample GAG concentrations and GCRs were measured in samples collected from 14 healthy dogs at the start of the 24-hour collection period. Twenty-four–hour total urine GAG excretions were determined from urine collected during a 24-hour period in the same 14 dogs. Total sulfated GAG concentrations were also measured in urine from these dogs after the urine had been stored at 4°C and -20°C for 1, 7, and 30 days.

Results—Urine GAG concentrations were not significantly different from baseline values after urine was stored at 4°C for up to 1 day and -20°C for up to 30 days. Neither single urine sample GAG concentration (R , 0.422) nor GCR (R , 0.084) was an adequate predictor of 24-hour total urine GAG excretion.

Conclusions and Clinical Relevance—Results of this study provide data that can be used to establish a reference range for 24-hour total urine GAG excretion in dogs and adequate conditions for sample storage. Contrary to findings in humans, there was no significant linear correlation between 24-hour total urine GAG excretion and single urine sample GCR in dogs, limiting clinical use of the single urine sample test.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of endotoxin administration on thyroid function test results and serum tumor necrosis factor-α (TNF-α) activity in healthy dogs.

Animals—6 healthy adult male dogs.

Procedures—Serum concentrations of thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5'-triiodothyronine (rT3), free T4 (fT4), and endogenous canine thyroid stimulating hormone (TSH), and TNF-α activity were measured before (day–1; baseline), during (days 0 to 3), and after (days 4 to 24) IV administration of endotoxin every 12 hours for 84 hours.

Results—Compared with baseline values, serum T3 concentration decreased significantly, whereas rT3 concentration increased significantly 8 hours after initial endotoxin administration. Serum T4 concentration decreased significantly at 8 and 12 hours after initiating endotoxin administration. Serum T4 concentration returned to reference range limits, then decreased significantly on days 6 to 12 and 16 to 20. Serum fT4 concentration increased significantly at 12, 24, and 48 hours after cessation of endotoxin treatment, compared with baseline values. Serum rT3 concentration returned to reference range, then decreased significantly days 5 and 7 after stopping endotoxin treatment. Serum TNF-α activity was significantly increased only 4 hours after initial endotoxin treatment, compared with baseline activity.

Conclusions and Clinical Relevance—Endotoxin administration modeled alterations in thyroid function test results found in dogs with spontaneous nonthyroidal illness syndrome. A decrease in serum T4 and T3 concentrations and increase in serum rT3 concentration indicate impaired secretion and metabolism of thyroid hormones. The persistent decrease in serum T4 concentration indicates that caution should be used in interpreting serum T4 concentrations after resolution of an illness in dogs. (Am J Vet Res 2003;64:229–234)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of deracoxib and aspirin on serum concentrations of thyroxine (T4), 3,5,3′-triiodothyronine (T3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) in healthy dogs.

Animals—24 dogs.

Procedure—Dogs were allocated to 1 of 3 groups of 8 dogs each. Dogs received the vehicle used for deracoxib tablets (PO, q 8 h; placebo), aspirin (23 to 25 mg/kg, PO, q 8 h), or deracoxib (1.25 to 1.8 mg/kg, PO, q 24 h) and placebo (PO, q 8 h) for 28 days. Measurement of serum concentrations of T4, T3, fT4, and TSH were performed 7 days before treatment (day −7), on days 14 and 28 of treatment, and 14 days after treatment was discontinued. Plasma total protein, albumin, and globulin concentrations were measured on days −7 and 28.

Results—Mean serum T4, fT4, and T3 concentrations decreased significantly from baseline on days 14 and 28 of treatment in dogs receiving aspirin, compared with those receiving placebo. Mean plasma total protein, albumin, and globulin concentrations on day 28 decreased significantly in dogs receiving aspirin, compared with those receiving placebo. Fourteen days after administration of aspirin was stopped, differences in hormone concentrations were no longer significant. Differences in serum TSH or the free fraction of T4 were not detected at any time. No significant difference in any of the analytes was detected at any time in dogs treated with deracoxib.

Conclusions and Clinical Relevance—Aspirin had substantial suppressive effects on thyroid hormone concentrations in dogs. Treatment with high dosages of aspirin, but not deracoxib, should be discontinued prior to evaluation of thyroid function.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine prevalence of retinal hemorrhages and microaneurysms in dogs with diabetes mellitus following cataract extraction by means of phacoemulsification and identify potential risk factors.

Design—Retrospective study.

Animals—52 dogs with diabetes mellitus and 174 dogs without.

Procedure—Medical records of dogs undergoing phacoemulsification between 1993 and 2003 were reviewed, and information was recorded on signalment, history, physical examination findings, ophthalmic examination findings, results of laboratory testing, electroretinographic findings, and surgical findings. Glycemic control was classified as poor, intermediate, or good on the basis of baseline blood glucose concentration, perioperative body weight loss, daily insulin dosage, and presence of glucosuria and ketonuria. Data from diabetic and nondiabetic dogs were analyzed to determine prevalence and risk factors for development of retinal hemorrhages or microaneurysms following phacoemulsification.

Results—11 of the 52 (21%) dogs with diabetes mellitus developed ophthalmoscopic signs of retinal hemorrhages or microaneurysms, compared with 1 of the 174 (0.6%) nondiabetic dogs. Median time from onset of diabetes mellitus to diagnosis of retinopathy was 1.4 years (range, 0.5 to 3.2 years). No risk factors for development of retinopathy were identified.

Conclusions and Clinical Relevance—Results suggest that retinal hemorrhages and microaneurysms may be more common and develop earlier in diabetic dogs than previously reported. This may affect treatment, as diabetic dogs survive longer with improved glycemic control. (J Am Vet Med Assoc 2004;225: 709–716)

Full access
in Journal of the American Veterinary Medical Association