Hypothyroidism In Dogs Research Articles

Assessment of the likelihood of hypothyroidism in dogs diagnosed with and treated for hypothyroidism at primary care practices: 102 cases (2016-2021).

There is a possibility that an incorrect diagnosis of hypothyroidism could be made in euthyroid dogs, and the prevalence of hypothyroidism in the dog population remains unknown. To retrospectively assess the percentage of dogs diagnosed with, and treated for, hypothyroidism at first opinion practice which are likely to be hypothyroid and require levothyroxine supplementation. One hundred two client-owned dogs were included in this study. The computerized databases of 7 first opinion practices were searched to identify dogs treated with levothyroxine supplementation. Three European College of Veterinary Internal Medicine-Companian Animals (ECVIM-CA) diplomates independently assigned 1 of 4 clinical assessments to each case as follows: confirmed or likely hypothyroid, hypothyroidism suspected but not confirmed, hypothyroidism considered unlikely, and no reason to suspect hypothyroidism. They commented as to whether or not they thought levothyroxine supplementation was appropriate. The clinical assessments of "confirmed or likely hypothyroid"; "Hypothyroidism suspected but not confirmed"; "Hypothyroidism considered unlikely"; and "No reason to suspect hypothyroidism" was assigned respectively by Clinician 1 to 38.2%, 5.9%, 3.9%, and 52% of cases, by Clinician 2 to 48%, 22.6%, 22.6%, 6.9% of cases, and by Clinician 3 to 55.9%, 11.8%, 13.7% and 18.6%. Clinician 1, Clinician 2, and Clinician 3 considered levothyroxine supplementation not indicated in 58.8%, 52.9%, and 45.1% of cases, respectively. These results support the concern that hypothyroidism might be overly and incorrectly diagnosed in first opinion practice, and that thyroid function testing should be performed only in those dogs with a high pretest probability of the disease.

Development and internal validation of diagnostic prediction models using machine-learning algorithms in dogs with hypothyroidism.

Hypothyroidism can be easily misdiagnosed in dogs, and prediction models can support clinical decision-making, avoiding unnecessary testing and treatment. The aim of this study is to develop and internally validate diagnostic prediction models for hypothyroidism in dogs by applying machine-learning algorithms. A single-institutional cross-sectional study was designed searching the electronic database of a Veterinary Teaching Hospital for dogs tested for hypothyroidism. Hypothyroidism was diagnosed based on suggestive clinical signs and thyroid function tests. Dogs were excluded if medical records were incomplete or a definitive diagnosis was lacking. Predictors identified after data processing were dermatological signs, alopecia, lethargy, hematocrit, serum concentrations of cholesterol, creatinine, total thyroxine (tT4), and thyrotropin (cTSH). Four models were created by combining clinical signs and clinicopathological variables expressed as quantitative (models 1 and 2) and qualitative variables (models 3 and 4). Models 2 and 4 included tT4 and cTSH, models 1 and 3 did not. Six different algorithms were applied to each model. Internal validation was performed using a 10-fold cross-validation. Apparent performance was evaluated by calculating the area under the receiver operating characteristic curve (AUROC). Eighty-two hypothyroid and 233 euthyroid client-owned dogs were included. The best performing algorithms were naive Bayes in model 1 (AUROC = 0.85; 95% confidence interval [CI] = 0.83-0.86) and in model 2 (AUROC = 0.98; 95% CI = 0.97-0.99), logistic regression in model 3 (AUROC = 0.88; 95% CI = 0.86-0.89), and random forest in model 4 (AUROC = 0.99; 95% CI = 0.98-0.99). Positive predictive value was 0.76, 0.84, 0.93, and 0.97 in model 1, 2, 3, and 4, respectively. Negative predictive value was 0.89, 0.89, 0.99, and 0.99 in model 1, 2, 3, and 4, respectively. Machine learning-based prediction models were accurate in predicting and quantifying the likelihood of hypothyroidism in dogs based on internal validation performed in a single-institution, but external validation is required to support the clinical applicability of these models.

Alterations in serum concentrations of visfatin and betatrophin in dogs with hypothyroidism.

Hypothyroidism in dogs is associated with obesity and altered lipid and carbohydrate metabolism. The adipokines, visfatin, and betatrophin, affect glucose tolerance. Betatrophin is involved in lipid regulation. Visfatin and betatrophin serum concentrations are altered in hypothyroid dogs. Dogs with naturally occurring hypothyroidism (n = 25) and healthy dogs (n = 25). Insulin, visfatin, and betatrophin serum concentrations were measured in all dogs and 19 of the hypothyroid dogs after 30 days of thyroxine treatment. Body condition score (BCS) was determined (1-9 scale). Visfatin concentrations were lower in hypothyroid compared with healthy dogs (mean, 95% confidence interval [CI]; 2.0 ng/mL, 1.2-3.3 vs 5.1 ng/mL, 3.3-7.8; P = .004) and increased post-treatment (3.1 ng/mL, 1.9-4.9 vs 2.6 ng/mL, 1.6-4.1; P = .05). Betatrophin concentrations were lower in lean to normal (body condition score [BCS], 3-5) hypothyroid dogs compared to lean to normal healthy dogs (52 pg/mL, 9-307 vs 597 pg/mL, 216-1648; P = .03), but were not different between overweight (BCS, 6-9) hypothyroid and healthy dogs (341 pg/L, 168-695 vs 178 pg/mL, 77-415; P = .26), and decreased post-treatment in overweight dogs (206 pg/mL, 87-488 vs 268 pg/mL, 112-640; P = .004). Visfatin concentrations were higher in overweight compared with lean to normal dogs (4.7 ng/mL, 3.3-6.6 vs 2.2 ng/mL, 1.2-4.2; P = .04). Betatrophin concentrations were positively correlated with BCS (r = .47, P = .02) and insulin concentrations (r = .48, P = .03) in hypothyroid dogs and negatively correlated with BCS (r = -.47, P = .02) and thyroid stimulating hormone concentrations (r = -.56, P = .01) in healthy dogs. Hypothyroidism in dogs is associated with alterations in visfatin and betatrophin concentrations that partially resolve with thyroxine treatment.

Contrast-enhanced ultrasonography of the thyroid gland in healthy dogs, hypothyroid dogs and dogs with non-thyroidal illness

Diagnosis of canine hypothyroidism remains challenging, as non-thyroidal illness (NTI)-syndrome and medical treatment can influence thyroid hormone concentrations. Conventional ultrasound may give additional hints, however high interobserver variability has been described. Contrast-enhanced ultrasound (CEUS) allows detection of changes in tissue perfusion. The purpose of the present study was to assess the possible diagnostic value of CEUS regarding diagnosis of hypothyroidism. CEUS of the thyroid gland was performed in 52 healthy dogs, 16 hypothyroid dogs, and 20 NTI patients. The following perfusion parameters were calculated: Thyroid/carotid artery (TG/CA) ratios for peak enhancement (PE) and area under the curve (AUC), time to peak (TTP) and wash-in and wash-out rates (WiR, WoR) of the thyroid gland. Impact of sedation on perfusion parameters was investigated in 8 calm healthy dogs which were examined before and after sedation using midazolam and butorphanol. Significantly higher median TG/CA ratios for PE were detected for the left and right thyroid lobe in dogs with hypothyroidism (0.97/0.96) compared to healthy dogs (0.85/0.85) and dogs with NTI (0.84/0.84). AUCs were also significantly increased in hypothyroid dogs when compared to other groups. Dogs with NTI showed significantly lower WiR and WoR compared to other groups. Values for TTP were not significantly different between groups. Sedation had only impact on results of TTP which was significantly prolonged in sedated dogs. In conclusion, CEUS of the thyroid gland can provide an additional tool for diagnosis of hypothyroidism in dogs and support its differentiation from NTI. Sedation has limited impact on CEUS results.

Hypothyroidism In Dogs: Causes, Pathophysiology, Clinical Signs, Diagnosis and Treatment

Hypothyroidism In Dogs: Causes, Pathophysiology, Clinical Signs, Diagnosis and Treatment

Hypothyroidism in dogs – prevalence, risk factors and neurological implications

Hypothyroidism is an endocrine pathology frequently encountered in dogs, whose diagnosis involves a series of difficulties due to the insidious onset of the disease and the non-specific clinical manifestations, which can mimic other diseases (metabolic, dermatological, neuromuscular, etc.). However, the development of modern diagnostic techniques and the widespread availability of specific determinations, such as total canine T4, free canine T4 and TSH, have led to an increase in diagnostic accuracy and the possibility of differentiating hypothyroidism from other diseases with similar manifestations. In recent years, numerous articles have investigated the etiology of the disease, however in our country there are few data regarding the prevalence and risk factors of this condition in the canine population. This article was carried out on 18 dogs diagnosed with hypothyroidism at the Emergency University Veterinary Hospital “Prof. Dr. Alin Bîrţoiu” between 2021 and 2022. All patients included in the study presented neurological manifestations. The diagnostic protocol included anamnesis, analysis of signalment, complete clinical examination, neurological examination and confirmation by serological investigations, the data obtained being compared with those provided by other similar studies.

Erkek köpeklerde kastrasyonun serum TSH düzeyi ile ilişkisi

One of the most frequently performed operations in small animal clinics is the removal of testicles in male animals. As a result of this operation, the behavior and metabolic activities of the animals may change more or less depending on the changes in the sex hormone activities. Thyroxine hormone secreted from the thyroid gland is the main hormone that regulates the metabolic rate of the body. It has been reported that the risk of hypothyroidism in dogs is increased with sterilization in some studies (Milne and Hayes 1981, Panciera 1994) and not associated with sterilization in other studies. In this study, 24 male healthy dogs aged 2-3 years and weighing an average of 20 kg were used. Blood samples were taken from 24 healthy male dogs (Group 1) and their serums were extracted without any surgical intervention. One month after castration, blood samples were taken from all animals again and the serums were extracted (Group 2). TSH level was measured in animals in all groups using the canine ELISA kit (BT lab canine thyroid stimulating hormone ELISA test kit). The effect of castration on TSH was found to be statistically insignificant.
 Keywords: Castration, dog, TSH

Pathology and diagnosis of hypothyroidism in dogs

Pathology and diagnosis of hypothyroidism in dogs

Understanding the effects of sustained supraphysiologic concentrations of luteinizing hormone in gonadectomized dogs: What we know and what we still need to learn

Removal of the gonads with surgical sterilization results in a loss of negative feedback to the hypothalamus and anterior pituitary. The sustained supraphysiologic luteinizing hormone (LH) concentrations in gonadectomized dogs can significantly alter organ function and even induce neoplastic changes. For example, gonad removal has a profound effect on thyroid function and is reported to be the most significant cause for the development of hypothyroidism in dogs. Thirty percent more gonadectomized dogs develop hypothyroidism compared with intact dogs. Within the canine thyroid, LH receptors are co-localized with thyroid stimulating hormone (TSH) receptors. Continuous LH receptor activation in gonadectomized dogs may interfere TSH receptor function by consuming second messengers involved in G-protein receptor cell signaling, preventing the action of TSH when it binds to its receptor in the thyroid, resulting in hypothyroidism. The incidence of anterior cruciate ligament ruptures is significantly increased following gonad removal independent of breed, sex, weight or body condition. Luteinizing hormone receptors are expressed in the cruciate ligament and continuous LH receptor activation may increase laxity in these ligaments, resulting in joint instability. Both male and female gonadectomized dogs are at a significantly increased risk for lymphoma and hemangiosarcoma. Luteinizing hormone receptors are also abundant in these tissues. Research in four canine hemangiosarcoma cell lines found that LH receptor activation induces cell proliferation. In addition, research in three canine T-cell lymphoma cell lines found that LH receptor activation induces cell proliferation, adhesion, and invasion as well as increases LH receptor expression. Research is needed to determine if LH reducing strategies using gonadotropin releasing hormone agonists will increase remission times in gonadectomized dogs with LH receptor-positive tumors. In conclusion, among the non-reproductive functions of gonads, suppression of LH secretion and resulting LH receptor overexpression appear necessary in maintaining endocrine, musculoskeletal, and anti-neoplastic health.

Frequency, breed predispositions and other demographic risk factors for diagnosis of hypothyroidism in dogs under primary veterinary care in the UK

BackgroundHypothyroidism is a commonly diagnosed endocrinopathy in dogs. This study aimed to investigate the frequency and risk factors for diagnosis of hypothyroidism in UK primary-care practice. Dogs diagnosed with hypothyroidism were identified by searching electronic patient records of primary-care practices participating in VetCompass. A cohort study design estimated one-year (2016) period prevalence and incidence risk for hypothyroidism. Multivariable binary logistic regression models were used to evaluate associations between demographic risk factors and hypothyroidism.ResultsFrom 905,553 dogs, 2,105 dogs were recorded with diagnosed hypothyroidism in 2016; 359 incident and 1,746 pre-existing, giving an annual prevalence of 0.23% (95% CI 0.22–0.24) and annual incidence risk of 0.04% (95% CI 0.04–0.04). Multivariable logistic regression identified 24 predisposed and nine protected breeds. Standard Doberman pinscher (odds ratio [OR] = 17.02, 95% CI 12.8–22.64), Tibetan terrier (11.25, 95% CI 8.27–15.32) and boxer (10.44, 95% CI 8.66–12.58) breeds showed high predisposition. Pug (OR 0.29, 95% CI 0.09–0.89), Yorkshire terrier (OR 0.38, 95% CI 0.24–0.59), Shih-tzu (OR 0.38, 95% CI 0.23–0.64) and Jack Russell terrier (OR 0.40, 95% CI 0.29–0.54) were the most protected breeds. Overall, being a purebred dog, being insured, having bodyweight above the breed-sex mean, increasing age, being neutered and rising adult bodyweight also showed increased odds being a dog living with a diagnosis of hypothyroidism.ConclusionsSeveral strong breed predispositions for diagnosis of hypothyroidism were identified that can assist with disorder prioritisation in ongoing efforts to improve breed health. Other risk factors were also identified that can assist veterinary surgeons during clinical work-up of suspected cases. Identification of novel evidence for protected breeds provides useful information for research into genetic mechanisms.

Free thyroxine measurement by analogue immunoassay and equilibrium dialysis in dogs with non-thyroidal illness

ObjectivesMeasurement of free T4 by analogue immunoassay (fT4a) is popular but its ability to differentiate hypothyroidism from non-thyroidal illness (NTI) is unclear. The aims were to assess fT4a concentrations in dogs with NTI and to explore diagnostic agreement with total T4 and free T4 measured by equilibrium dialysis (fT4d). MethodsfT4a was measured in dogs classified with mild, moderate and severe NTI. Total T4 and fT4d were measured in a subgroup of these dogs. Results146 dogs were included of which 84, 35 and 27 had mild, moderate and severe NTI, respectively. Median (range) fT4a concentrations (pmol/L) were significantly lower (P = 0.023 and P < 0.001) in dogs with severe (3.86 (3.86–23.60)) compared with moderate (11.10 (3.86–34.70)) and mild (15.25 (3.86–48.60)) NTI. Overall, 49 (33.6% [95% CI, 26.4–41.6]) dogs had low fT4a concentration. All thyroid hormones were measured in 74 dogs. Agreement was substantial between total T4 and fT4a (κ=0.79 [95% CI, 0.65–0.92]) and fT4a and fT4d (κ =0.63 [95% CI, 0.47-0.79]) but moderate between total T4 and fT4d (κ=0.49 [95% CI, 0.32–0.66]). Of 42 dogs with low total T4 concentration, five (11.9% [95% CI, 5.19–24.99]) and 18 (42.9% [95% CI, 29.12–57.80]) had fT4a and fT4d within reference interval, respectively. Conclusions and clinical importancefT4a and fT4d cannot be used interchangeably. Measurement of fT4a provides limited further diagnostic information over measurement of total T4 in dogs with NTI. This study raises concerns regarding the ability of fT4a to differentiate NTI from hypothyroidism in dogs with low total T4 concentrations.

Association between dilated cardiomyopathy and hypothyroidism in dogs

It is a known fact that thyroid hormones have an influence on the heart function. Opinions on hypothyroidism and its effect on dilated cardiomyopathy (DCM) development are controversial and often contradictory. This prospective study examined the potential association between hypothyroidism and DCM in dogs. A total of 35 dogs with DCM were included in the study. Preclinical DCM was diagnosed in 18 patients, and clinical DCM was diagnosed in 17 patients, four of which were also diagnosed with hypothyroidism. There was a positive correlation between the thyroid-stimulating hormone and body weight, left atrium size and the serum NT-proBNP concentration in patients with preclinical DCM. Euthyroid dogs with DCM had higher total thyroxine values and more ventricular premature complexes than hypothyroid dogs. Although our study did not confirm a direct relationship between hypothyroidism and DCM as a possible cause, other correlations were detected that had not yet been described in veterinary medicine.

Aggression and Hypothyroidism in Dogs, an-Overview

One of the most often diagnosed endocrine disorder in middle-aged dogs is hypothyroidism. The clinicopathological aspects of the disease are well known and established by the scientific community. For over 20 years the relationship between aggression and hypothyroidism has been reported in the literature. Still the link remains speculative due to lack of overhaul scientific data. The aim of this study is to present data from the literature relating to the association of aggression with hypothyroidism in dogs.

Epidemiological Study on Hypothyroidism in Dogs in Egypt

Canine hypothyroidism is one of the common endocrinopathies in dogs. Clinical signs are variable as it’s a multi-systemic disease. This study was carried out to investigate epidemiology of hypothyroidism in dogs regarding to clinical signs under effect of age, sex, season and breed and confirmation with evaluation of TT4. A total number of 441 dogs admitted to a private clinic in Cairo Governorate during the period of 2018 till 2020 were subjected to comprehensive clinical examination of which 82 hypothyroid dogs were recorded and incidence of different hypothyroidism features was evaluated. Hypothyroidism showed higher incidence in middle aged dogs (1-5 years), in males compared to females, in autumn than other seasons, and in large dog breeds. TT4 levels in this study ranged between 0.5-1 μg/dl with mean 0.8 ± 0.017. TT4 should be put in consideration during diagnosis of suspected cases related to dermatological, gynecological, otitis, CNS, tumors, dwarfism, cardiac, GIT, low BCS, obesity, eye and mixed signs. Special care should be associated with sharp decrease in TT4 in cases of CNS. The obtained data should be put under consideration in diagnosing of canine hypothyroidism and evaluation of clinical signs associated with it and therapeutic regimen to be applied for correction of such dysfunctions.

Canine Adult-Onset Hypothyroidism: Prevalence, Clinical and Laboratory Findings with Special Reference to Therapeutic Approach

Hypothyroidism is one of the most common endocrinopathies in dogs, it is defined as a decrease in production of thyroid hormones. Hypothyroidism results in vague clinical of signs but metabolic and dermatological signs are the most reported manifestations. This investigation aimed to study canine hypothyroidism in terms of clinical, haemato- biochemical, and thyroid panel alterations and evaluate response to treatment in adult onset hypothyroidism in dogs’ cosmopolitan in Cairo and Giza governorates. To crude determination of disease in dog cosmopolitan in Cairo and Giza governorates, multicenter study was conducted. In the period from December-2019 to May-2020, 220 dogs with various dermatologic signs represented to different clinics, after ruling out other causes, 40 with signs consistent with hypothyroidism were subjected to initial screening for hypothyroidism using TT4. Only 15 dogs showed decrease in TT4 and these dogs were further investigated, additional 8 clinically healthy dogs enrolled as control group. Blood sample was taken from both hypothyroid dogs [N=15] and control dogs [N=8] for hematology analysis, TT4, fT4, TSH. Cholesterol, ALT and ALP. Diseased group [15 dogs] were treated with levothyroxine and re-evaluated after 1-month period. Overall prevalence of hypothyroidism in this investigation was 7.5 percent. Significant decrease in RBCs, PCV, TT4 and fT4 along with non-significant increase in TSH and cholesterol were recorded in hypothyroid patients compared to control group. Treatment with levothyroxine caused thyroid hormones to be within normal reference range. The Prevalence of hypothyroidism in studied cases in this investigation was 7.5 % and is similar to the reported prevalence; diagnosis of hypothyroidism should be relying on combination of clinical and laboratory data. Usage of human levothyroxine can successfully manage caninehypothyroidism.

Clinical signs of hypothyroidism in domestic dogs

The research was conducted during 2016–2019 on the basis of veterinary clinics in Poltava - veterinary clinic at the Department of Therapy named after Professor P.Lokes of Poltava State Agrarian Academy, “Vet Line”, “Vet Comfort” and the laboratory of the Department of Therapy named after Professor P. I. Lokes of Poltava State Agrarian Academy. During the research we studied 11 dogs, which were diagnosed with hypothyroidism. The animals belonged to different breeds, had different sexes (6 females and 5 males) and age. For control we took 15 dogs without visible signs of any pathology. We compared the breed susceptibility of dogs with hypothyroidism and dogs with alimentary obesity. Thus, we found that most breeds are common to animals in both pathologies. However, in our sample for hypothyroidism there was no such breed as a pug, and outbred individuals, which accounted for a significant percentage of dogs with alimentary obesity. One of the most common clinical symptom is the presence of symmetrical alopecia on the sides on the background of dull and disheveled hair (90.9 %). Mucosal anemia was observed in a significant proportion of animals (81.8 %). The symptom of bradycardia and shortness of breath during exercise is observed in 72.7 % of experimental animals, which indicates the development of pathological changes in the cardiovascular system. It was found that all animals showed depression, weakness and fatigue (100.0 %). Polydipsia and hypothermia were much less common in 45.5 % of dogs, and corneal dystrophy in 36.4% of cases. The last clinical manifestation occurred in animals with the most severe pathology. According to the literature, it is known that hypothyroidism in dogs is often a symptom of obesity. According to our data, obesity (overweight) was registered in 63.6 % of experimental animals. With the diagnosis of “hypothyroidism” in dogs, we identified two experimental groups: 1 – animals with normal fatness; 2nd – with a clinical symptom of obesity. We can note a significant increase in adipose tissue in dogs with hypothyroidism of the 2nd experimental group (45.1 ± 1.70 %), which indicates the presence of endocrine obesity, as evidenced by visual assessment of fatness (4.7 ± 0.18 points). Such changes develop due to insufficient production of thyroid hormones. The latter play an important role in regulating metabolism in the body. Due to their deficiency, the metabolism in animals slows down and, as a result, there is a risk of obesity.

Determination of cTSH plasmatic concentration in diagnosis of primary hypothyroidism in dogs: case report

Primary hypothyroidism in dogs presents nonspecific and systemic clinical signs, which precludes diagnosis only through clinical examination, blood count and routine serum biochemistry. Thus, thyroid function tests, together with clinical signs, should be performed for the definitive diagnosis of this endocrinopathy. Four dogs, one male and three females, aged 4 to 10 years, with clinical signs suggestive of hypothyroidism were evaluated for free T4 (fT4) and canine TSH (cTSH) plasma concentrations. In all dogs diagnosed with primary hypothyroidism, an increase was observed. cTSH concentration and free T4 decrease. As they were treated with sodium levothyroxine, there was an improvement in the reevaluation of TSH and fT4 parameters. Blood count and serum biochemistry were performed to help to rule out comorbidities and diseased euthyroid. Definitive diagnosis and follow-up of primary hypothyroidism treatment should be based on determinations of fT4 and cTSH plasma concentrations. It is recommended to rule out the sick euthyroid condition for successful hormone replacement therapy.

Whole-genome genotyping and resequencing reveal the association of a deletion in the complex interferon alpha gene cluster with hypothyroidism in dogs

BackgroundHypothyroidism is a common complex endocrinopathy that typically has an autoimmune etiology, and it affects both humans and dogs. Genetic and environmental factors are both known to play important roles in the disease development. In this study, we sought to identify the genetic risk factors potentially involved in the susceptibility to the disease in the high-risk Giant Schnauzer dog breed.ResultsBy employing genome-wide association followed by fine-mapping (top variant p-value = 5.7 × 10− 6), integrated with whole-genome resequencing and copy number variation analysis, we detected a ~ 8.9 kbp deletion strongly associated (p-value = 0.0001) with protection against development of hypothyroidism. The deletion is located between two predicted Interferon alpha (IFNA) genes and it may eliminate functional elements potentially involved in the transcriptional regulation of these genes. Remarkably, type I IFNs have been extensively associated to human autoimmune hypothyroidism and general autoimmunity. Nonetheless, the extreme genomic complexity of the associated region on CFA11 warrants further long-read sequencing and annotation efforts in order to ascribe functions to the identified deletion and to characterize the canine IFNA gene cluster in more detail.ConclusionsOur results expand the current knowledge on genetic determinants of canine hypothyroidism by revealing a significant link with the human counterpart disease, potentially translating into better diagnostic tools across species, and may contribute to improved canine breeding strategies.

Electrocardiographic and echocardiographic evaluation in dogs with hypothyroidism before and after levothyroxine supplementation: A prospective controlled study.

BackgroundImprovement in cardiac function has been demonstrated after thyroxine treatment in humans with hypothyroidism using the myocardial performance index (MPI). Cardiac changes after thyroxine supplementation are poorly documented in dogs with spontaneous hypothyroidism and comparison with clinically healthy dogs is lacking.ObjectivesTo evaluate the electrical activity and mechanical function of the heart in dogs with primary hypothyroidism at baseline (T0) and after thyroxine supplementation (T60).AnimalsForty client‐owned dogs with hypothyroidism and 20 clinically healthy dogs.MethodsProspective cohort study. Selected electrocardiographic and echocardiographic variables, including the MPI, were measured in all dogs at T0 and in 30 hypothyroid dogs at T60.ResultsHypothyroid dogs had significantly decreased median or mean heart rate (HR), P wave amplitude, and R wave amplitude (P = .04, P = .002, and P = .003, respectively) and E‐point‐to‐septal separation normalized to body weight (EPSSn) and trans‐mitral E wave velocity (E max; P < .001 and P = .025, respectively) at T0 compared to control dogs. At T60, significantly increased median or mean HR, P wave amplitude, fractional shortening, and E max (P < .001, P = .004, P = .002, and P = .009, respectively) and significantly decreased left ventricular end‐diastolic volume index, and normalized systolic diameter and EPSSn (P = .03, P = .03, and P = .001, respectively) were found.Conclusions and Clinical ImportanceHypothyroidism in dogs induces mild and reversible changes of electromechanical cardiac function. The MPI does not have clinical importance in identifying cardiac dysfunction in affected dogs.

Relationship between Total Homocysteine, Folic Acid, and Thyroid Hormones in Hypothyroid Dogs.

BackgroundBoth elevated homocysteine and decreased folic acid concentrations are observed in human patients with hypothyroidism and can influence the development of numerous secondary disorders.ObjectivesThe aim of the study was to assess total homocysteine concentration in serum and to examine its relationship with the concentration of folic acid and thyroid hormones (tT4 and fT4).AnimalsTen healthy and 19 hypothyroid client‐owned dogs.MethodsDogs with clinical signs of hypothyroidism had the diagnosis confirmed by additional tests. Total homocysteine, folic acid, total thyroxine, and free thyroxine concentrations in serum were evaluated.ResultsHypothyroid dogs were diagnosed with increased homocysteine (median 22.20 μmol/L; range, 16.50–37.75) and decreased folic acid (median 20.62 nmol/L; range, 10.54–26.35) concentrations, as compared to healthy dogs (11.52 μmol/L; range, 10.00–16.65 and 30.68 nmol/L; range, 22.84–38.52, respectively). In sick dogs, total homocysteine was inversely correlated with folic acid (ρ = −0.47, P < 0.001), total thyroxine (ρ = −0.69, P = 0.0092), and free thyroxine (ρ = −0.56, P = 0.0302).ConclusionsHypothyroidism in dogs causes hyperhomocysteinemia. Concomitant mild folic acid decrease in hypothyroid dogs might be as a result of hyperhomocysteinemia.