Hypoadrenocorticism in small animals

Diagnostic predictivity of transtubular potassium gradient for primary hypoadrenocorticism in hyperkalemic dogs: a cross-sectional study

OBJECTIVES

Transtubular potassium gradient has never been evaluated in the diagnosis of primary hypoadrenocorticism in dogs. The objective of this study is to evaluate the diagnostic utility of transtubular potassium gradient for the diagnosis of primary hypoadrenocorticism in dogs with serum K+  > 5.5 mol/L.

MATERIALS AND METHODS

Cross-sectional study including dogs with primary hypoadrenocorticism and dogs with other disease. Differences in signalment and laboratory parameters between groups were assessed by binary logistic regression modelling. Variables significantly associated with primary hypoadrenocorticism were evaluated for their diagnostic accuracy of this condition by receiver operator characteristic curve analysis and by multivariable logistic regression analysis, respectively.

RESULTS

Dogs with primary hypoadrenocorticism (n=39) were significantly younger than hyperkalemic dogs without primary hypoadrenocorticism (n=41). Moreover they had higher serum and urinary concentrations of Na+ and Na+ :K+ , but lower transtubular potassium gradient than hyperkalemic dogs without hypoadrenocorticism. Serum Na+ (sNa+ ) had the highest diagnostic accuracy (area under the curve [AUC]: 0.87, 95% confidence interval, 0.78 to 0.96), followed by the transtubular potassium gradient (AUC: 0.81, 0.72 to 0.91), however the accuracy of the two AUCs was not statistically different. The transtubular potassium gradient-sNa+ additive index (i.e. transtubular potassium gradient+sNa+ /10) had a greater accuracy (AUC: 0.88, 0.79 to 0.94) than transtubular potassium gradient or sNa+ , although it was not statistically superior to the latter. The multivariable logistic regression model showed that transtubular potassium gradient (adjusted odds ratio [aOR]: 0.51, 0.3 to 0.84), sNa+ (aOR: 0.86, 0.78 to 0.95) and spayed female (aOR: 24.96, 2.32 to 267.66) were associated with primary hypoadrenocorticism.

CLINICAL SIGNIFICANCE

Transtubular potassium gradient-sNa+ additive index can contribute to decision-making on diagnosis of primary hypoadrenocorticism in dogs presenting with hyperkalaemia.

Metabolomic Abnormalities in Serum from Untreated and Treated Dogs with Hyper- and Hypoadrenocorticism

The adrenal glands play a major role in metabolic processes, and both excess and insufficient serum cortisol concentrations can lead to serious metabolic consequences. Hyper- and hypoadrenocorticism represent a diagnostic and therapeutic challenge. Serum samples from dogs with untreated hyperadrenocorticism (n = 27), hyperadrenocorticism undergoing treatment (n = 28), as well as with untreated (n = 35) and treated hypoadrenocorticism (n = 23) were analyzed and compared to apparently healthy dogs (n = 40). A validated targeted proton nuclear magnetic resonance (¹H NMR) platform was used to quantify 123 parameters. Principal component analysis separated the untreated endocrinopathies. The serum samples of dogs with untreated endocrinopathies showed various metabolic abnormalities with often contrasting results particularly in serum concentrations of fatty acids, and high- and low-density lipoproteins and their constituents, which were predominantly increased in hyperadrenocorticism and decreased in hypoadrenocorticism, while amino acid concentrations changed in various directions. Many observed serum metabolic abnormalities tended to normalize with medical treatment, but normalization was incomplete when compared to levels in apparently healthy dogs. Application of machine learning models based on the metabolomics data showed good classification, with misclassifications primarily observed in treated groups. Characterization of metabolic changes enhances our understanding of these endocrinopathies. Further assessment of the recognized incomplete reversal of metabolic alterations during medical treatment may improve disease management.

Evaluation of Adrenal Cortical Function in Neonatal and Weanling Laboratory Beagle Dogs

The most common target organ for toxicity in the endocrine system is the adrenal gland, and its function is dependent upon the hypothalamus and pituitary gland. Histopathologic examination of the adrenal glands and pituitary gland is routinely performed in toxicity studies. However, the function of the adrenal gland is not routinely assessed in toxicity studies. Assessment of adrenal cortical function may be necessary to determine whether a histopathologic finding in the adrenal cortex results in a functional effect in the test species. As juvenile toxicity studies are more commonly performed in support of pediatric indications for pharmaceuticals, it is important to establish historical control data for adrenal gland function. In this study, adrenal cortical function was assessed in control neonatal and weanling beagle dogs as part of an ongoing juvenile toxicology program. Measurements of serum adrenocorticotropic hormone (ACTH), cortisol prior to and following administration of exogenous ACTH, and aldosterone were conducted beginning at 2 weeks of age continuing through 26 weeks of age. Serum electrolyte concentrations were determined at 4, 13, and 26 weeks of age. Dogs as young as 2 weeks of age synthesize and secrete adrenal cortical hormones and exhibit a functional hypothalamic pituitary adrenal axis.

Repeated bouts of pulmonary tuberculosis in a hunting cat: reinfection or recrudescence?

CASE SUMMARY

A 7-year-old neutered male Siamese cat was referred for investigation of weight loss and hypercalcaemia (3.3 mmol/l; reference interval 2-3 mmol/l). Haematology, serum biochemistry, thoracic imaging, bronchoalveolar lavage (BAL), Ziehl-Neelsen staining of the BAL fluid and interferon gamma release assay (IGRA) were compatible with pneumonia caused by the less pathogenic member of the Mycobacterium tuberculosis complex, that is, M microti (the 'vole bacillus'), which is common in cats in the UK. Treatment with azithromycin, rifampicin and marbofloxacin was given for 2 months, followed by 4 months of azithromycin and marbofloxacin. Treatment recommendations for tuberculous pneumonia have since changed. The cat remained asymptomatic for 1 year but went on to develop M microti pneumonia on five other occasions, and was treated for 6-12 months on each occasion. The patient's clinical signs, hypercalcaemia and radiographic/CT pulmonary pathology always resolved completely, and the IGRA became negative, before antimycobacterial treatment was stopped. This suggests cure followed by reinfection owing to avid hunting behaviour. Alternatively, this could represent recrudescence of dormant disease. This case has previously been included in a study that described a series of cases of feline tuberculosis.

RELEVANCE AND NOVEL INFORMATION

This case shows that M microti infection in cats can present as recurrent episodes of pneumonia, even after prolonged treatment courses.

Semiquantitative acid-base analysis in dogs with typical hypoadrenocorticism

OBJECTIVE

To describe the semiquantitative acid-base status of dogs with untreated naturally occurring typical hypoadrenocorticism and to compare this to the status determined by traditional acid-base analysis.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Thirty-three dogs with newly diagnosed typical hypoadrenocorticism between 2000 and 2017.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Dogs were included if they had newly diagnosed hypoadrenocorticism, post-ACTH stimulation serum cortisol concentration <2 μg/dL, and blood collected within 6 hours of presentation for acid-base, electrolyte, and serum biochemical assays. Dogs were excluded if the Na⁺ :K⁺ ratio was ≥28 or the dog had received a mineralocorticoid-containing corticosteroid medication within the preceding month. Traditional acid-base analysis identified normal acid-base status in 1 dog, simple respiratory acid-base abnormalities in 2 of 33 dogs, and simple metabolic acidosis in 14 of 33 dogs. A mixed disorder was most common, noted in 16 of 33 dogs. The semiquantitative approach identified metabolic abnormalities in all cases. All dogs had ≥1 acidifying process, and 29 of 33 had both acidifying and alkalinizing processes. Acidosis attributable to excess free water was present in all dogs, and an acidifying phosphate effect was present in 27 of 33. Hyperlactatemia contributed to the acidosis in 8 of 33 dogs, with a median (range) lactate concentration of 1.5 mmol/L (13.5 mg/dL) (0.3-4.2 mmol/L [2.7-37.8 mg/dL]).

CONCLUSIONS

Dogs with untreated Addison's disease have complex acid-base derangements. The semiquantitative approach to acid-base analysis provides greater insight into the underlying mechanisms of metabolic acid-base abnormalities in these dogs, particularly because lactic acidosis appears to be a minor influence in most cases.

DLA class II haplotypes show sex-specific associations with primary hypoadrenocorticism in Standard Poodle dogs

Addison's disease (AD) is a life-threatening endocrine disorder that occurs spontaneously in both humans and dogs. Associations between MHC class II genes and AD have been shown in several human studies. Our goal was to identify MHC class II associations with AD in a large population of Standard Poodles, a breed highly predisposed to AD. We sequenced exon 2 of the class II genes DLA-DRB1, DLA-DQA1, and DLA-DQB1 in 110 affected and 101 unaffected Standard Poodles and tested for association with AD. After correcting for population structure, two haplotypes were found to confer risk of developing AD in a sex-specific manner: DLA-DRB1*015:01-DQA1*006:01-DQB1*023:01 in males (x²p = 0.03, OR 2.1) and DLA-DRB1*009:01-DQA1*001:01-DQB1*008:01:1 in females (x²p = 0.02, OR 8.43). Sex-specific associations have been previously described in human populations, but this is the first report of this kind in dogs. Consistent with findings in other studies, we found the DLA-DQA1*006:01 allele (x²p = 0.04) to be associated with AD in males independent of haplotype. In females, the haplotype DLA-DRB1*009:01-DQA1*001:01-DQB1*008:01:1 confers a very high risk for developing AD, although its frequency was rare (9 of 124 females) in our study population. Further studies are warranted to validate the findings of this exploratory dataset and to assess the usefulness of this haplotype as a risk marker for AD in female Standard Poodles. Our results highlight the importance of evaluating MHC class II disease associations in large populations, and accounting for both biological sex and population structure.

Cortisol Response in Healthy and Diseased Dogs after Stimulation with a Depot Formulation of Synthetic ACTH

Background

The ACTH stimulation test is used to evaluate the adrenocortical reserve. Recently, the availability of the synthetic ACTH formulation was limited, causing major problems in clinical practice.

Objectives

The objective of this study was to evaluate poststimulation peak cortisol concentrations and the duration of the stimulatory effect of a depot ACTH preparation in dogs.

Animals

Twenty‐two healthy dogs, 10 dogs with suspected hypoadrenocorticism (HA) and 15 dogs with suspected hyperadrenocorticism (HC).

Methods

Prospective study. An ACTH stimulation test using a synthetic depot tetracosactide, administered intramuscularly (5 μg/kg or at least 0.1 mL) was performed. Blood samples for determination of cortisol were taken immediately before and 1, 2, 3, 4, 6, and 24 hours after stimulation.

Results

Peak cortisol concentrations were reached after 2–4 hours in all dogs. Cortisol concentrations 1 hour after stimulation were >9 μg/dL in all healthy dogs and >5 μg/dL in all dogs in which HA was excluded. None of the dogs with HA showed a cortisol‐increase above the detection‐limit of the assay. After 6 hours, cortisol concentrations had decreased in the healthy and HC group and were back to baseline after 24 hours.

Conclusions and Clinical Importance

The depot formulation can be used in place of the short‐acting ACTH to evaluate the adrenocortical reserve. Blood for peak cortisol concentrations should be drawn 3 hours after stimulation in cases in which HC is suspected; in HA‐suspected cases, blood sampling can take place after 1 hour. As the stimulatory effect is gone after 24 hours, interference with other hormonal tests is unlikely after that time.

Histologic and clinical features of primary and secondary vasculitis

Inflammation of the blood vessel wall has been reported infrequently in dogs, and it may occur without apparent cause (primary vasculitis) or as a pathologic reaction to a range of initiating insults (secondary vasculitis). The aims of our study were to report histologic, clinical, and survival data from a large series of cases with primary and secondary vasculitis, and to compare the clinical parameters and outcome data between groups. Clinical data was collected retrospectively from the medical records of 42 client-owned dogs with a histologic diagnosis of primary or secondary vasculitis, and follow-up information was obtained. Cases were grouped according to clinical and histologic descriptors, and biochemical, hematologic, and survival data was compared between groups. Several forms of primary vasculitis were observed, and vascular inflammation was observed in conjunction with numerous other diseases. Female dogs were more likely to develop primary vasculitis, and serum globulin concentration was greater in dogs with primary vasculitis compared to those with underlying disease. All dogs with primary vasculitis of the central nervous system died or were euthanized shortly after presentation, but other forms of primary vasculitis could be managed effectively. In conclusion, presentation of clinical cases in this series was variable, and there did not appear to be well-defined vasculitic syndromes as described in people.

A review of the genetics of hypoadrenocorticism

Hypoadrenocorticism is an uncommon disease in dogs and rare in humans, where it is known as Addison disease (ADD). The disease is characterized by a deficiency in corticosteroid production from the adrenal cortex, requiring lifelong hormone replacement therapy. When compared with humans, the pathogenesis of hypoadrenocorticism in dogs is not well established, although the evidence supports a similar autoimmune etiology of adrenocortical pathology. Several immune response genes have been implicated in determining susceptibility to Addison disease in humans, some of which are shared with other autoimmune syndromes. Indeed, other types of autoimmune disease are common (approximately 50%) in patients affected with ADD. Several lines of evidence suggest a genetic component to the etiology of canine hypoadrenocorticism. Certain dog breeds are overrepresented in epidemiologic studies, reflecting a likely genetic influence, supported by data from pedigree analysis. Molecular genetic studies have identified similar genes and signaling pathways, involved in ADD in humans, to be also associated with susceptibility to canine hypoadrenocorticism. Immune response genes such as the dog leukocyte antigen (DLA) and cytotoxic T-lymphocyte-associated protein 4 (CTLA4) genes seem to be particularly important. It is clear that there are genetic factors involved in determining susceptibility to canine hypoadrenocorticism, although similar to the situation in humans, this is likely to represent a complex genetic disorder.

Trilostane therapy for treatment of spontaneous hyperadrenocorticism in cats: 15 cases (2004-2012)

BACKGROUND

Medical treatment with trilostane improves clinical signs, causes unclear insulin requirement changes, and variable survival times in cats.

OBJECTIVES/HYPOTHESIS

To characterize the long-term efficacy of trilostane in treating cats with hyperadrenocorticism (HAC).

ANIMALS

Fifteen client-owned cats with spontaneous HAC.

METHODS

Multicenter descriptive retrospective study with a search performed on all medical records for cats diagnosed with spontaneous HAC.

RESULTS

Clinical signs (13 of 15 cats) and ACTH stimulation testing results (13 of 15) improved with trilostane therapy. Diabetes mellitus was reported in 9/15 cases. Insulin requirements decreased by 36% within 2 months in 6/9 diabetic cats. Median survival time was 617 days for all cats (range 80-1,278 days). Complications included weight loss, urinary tract infections, chronic kidney disease, seizures, and recurrent pancreatitis. Hypocortisolemia was documented in 1 case. Cause of death occurred as a result of nonadrenal or nondiabetic illnesses (renal failure, seizures [caused by hypoglycemia or unknown]), or lymphoma.

CONCLUSIONS AND CLINICAL IMPORTANCE

Trilostane ameliorates clinical signs of HAC in cats, is tolerated well in the long term, and can lead to improved regulation of diabetes.

Diagnosis and management of atypical hypoadrenocorticism in a variable flying fox (Pteropus hypomelanus)

A 19-yr-old intact female variable flying fox (Pteropus hypomelanus) presented with lethargy, behavior changes, and substantial weight loss. Initial clinical pathology revealed hypoglycemia and reduced ionized serum calcium, and imaging, including computed tomography, did not lead to a diagnosis. An adrenocorticotropic hormone (ACTH) stimulation test revealed baseline and post-ACTH cortisol concentrations that were lower than reported normal baseline cortisol concentrations in this species. Treatment with prednisolone resolved the clinical signs and laboratory abnormalities. Repeated attempts to decrease the prednisolone dose caused recurrence of clinical signs and weight loss. Based on diagnostic test results and response to therapy, a diagnosis of atypical hypoadrenocorticism was made.

Severe hypoglycaemia in a cat with primary hypoadrenocorticism

This case report describes a 3-year-old, castrated male, mixed-breed cat with historical, clinical and laboratory findings compatible with primary hypoadrenocorticism, confirmed by adrenocorticotropic hormone stimulation test. Severe but asymptomatic hypoglycaemia was an unexpected biochemical finding and resolved after fludrocortisone acetate and prednisolone treatment. This case demonstrates that hypoadrenocorticism should be included in the differentials list of severe hypoglycaemia in cats.

Autoimmune Addison disease: pathophysiology and genetic complexity

Autoimmune Addison disease is a rare autoimmune disorder with symptoms that typically develop over months or years. Following the development of serum autoantibodies to the key steroidogenic enzyme, 21-hydroxylase, patients have a period of compensated or preclinical disease, characterized by elevations in adrenocortocotropic hormone and renin, before overt, symptomatic adrenal failure develops. We propose that local failure of steroidogenesis, causing breakdown of tolerance to adrenal antigens, might be a key factor in disease progression. The etiology of autoimmune Addison disease has a strong genetic component in man, and several dog breeds are also susceptible. Allelic variants of genes encoding molecules of both the adaptive and innate immune systems have now been implicated, with a focus on the immunological synapse and downstream participants in T lymphocyte antigen-receptor signaling. With the exception of MHC alleles, which contribute to susceptibility in both human and canine Addison disease, no major or highly penetrant disease alleles have been found to date. Future research into autoimmune Addison disease, making use of genome-wide association studies and next-generation sequencing technology, will address the gaps in our understanding of the etiology of this disease.

Effect of estrous cycle phase on clinical pathology values in beagle dogs

BACKGROUND

In dogs, the diestrus phase is considerably longer than in most domestic animals, and is characterized by high circulating progesterone concentrations that may influence clinical pathology values.

OBJECTIVE

The objective of this retrospective study was to investigate differences in clinical pathology data in dogs in diestrus compared with data from dogs in all other phases of the estrous cycle.

METHODS

Phase of the estrous cycle was determined by histologic evaluation of reproductive tissues from 86 control female Beagles that had participated in 23 toxicity studies. Serum biochemical, hematologic, and urinalysis values from dogs in diestrus were compared with data from dogs in all other estrous cycle phases using a 2-tailed t-test.

RESULTS

In Beagles in diestrus (n = 38), serum cholesterol concentrations and eosinophil counts were 35% (P < .0001) and 45.8% (P = .0035) higher, respectively, than for Beagles in all other phases of the estrous cycle (n = 48). Furthermore, Beagles in diestrus had 14% lower AST activity (P = .0011), 1% lower chloride concentration (P = .0224), 7.8% lower hemoglobin concentration (P < .0001), 7.8% lower RBC count (P < .0001), and 7.6% lower hematocrit (P < .0001) compared with female dogs in all other phases of the estrous cycle. Urine values did not differ significantly between groups.

CONCLUSIONS

Differences in clinical pathology values between dogs in different phases of the estrous cycle could potentially confound interpretation of data in toxicity studies, which often have small group sizes. Interpretation of clinical pathology data in female dogs should be performed with due consideration given to the phase of the estrous cycle.

Adrenocortical insufficiency in horses and foals

The adrenal cortices produce various steroid hormones that play vital roles in several physiologic processes. Although permanent adrenocortical insufficiency is rare in all species, emerging evidence in both human and equine medicine suggests that transient reversible adrenocortical dysfunction resulting in cortisol insufficiency frequently develops during critical illness. This syndrome is termed relative adrenal insufficiency (RAI) or critical illness-related corticosteroid insufficiency (CIRCI) and can contribute substantially to morbidity and mortality associated with the primary disease. This review discusses the mechanisms, diagnosis, and clinical consequences of adrenocortical insufficiency, with particular focus on the current understanding of RAI/CIRCI in horses and foals.

Recent advances in adrenal autoimmunity

Autoimmune Addison's disease (AAD) results from the immune-mediated destruction of adrenocortical cells. AAD is a major component of the autoimmune polyendocrine syndromes type 1 (APS 1) and type 2. The adrenal autoimmune process is made evident by the apperance of circulating autoantibodies against the steroidogenic enzyme 21-hydroxylase. Detection of 21-hydroxylase in patients with endocrine autoimmune diseases enables the identification of subjects with preclinical AAD. An impaired response to a corticotrophin stimulation test marks the irreversible stage of preclinical AAD and predicts progression towards clinical AAD in over 80% of cases. APS 1 is caused by mutations of the autoimmune regulator (AIRE) gene, which encodes an activator of transcription, Aire, that induces the expression of autoantigens in thymic medullary epithelial cells and promotes immunological tolerance. Isolated and APS 2-related AAD is an autoimmune disease with evidence for complex genetic susceptibility caused by T-cell-mediated destruction of adrenocortical cells, with a major contribution of HLA genes. The target cells in the adrenal cortex participate in the immune reaction by releasing chemokines, such as CXCL-10, that attract Th1 cells.