A case-control survey study of environmental risk factors for primary hypoadrenocorticism in dogs

BACKGROUND

Primary hypoadrenocorticism in dogs is thought to be multifactorial with roles for both genetic and environmental factors. The contributions of environmental factors remain unexplored.

OBJECTIVE

Identify environmental and lifestyle exposures associated with primary hypoadrenocorticism in 2 dog breeds with high risk of developing the disease.

ANIMALS

Animals were not used in this study. Owners of Standard Poodles (STPDs) and Portuguese water dogs (POWDs) participated in a survey.

METHODS

Retrospective case-control study. Dog owners were invited to participate in an online survey through convenience sampling. Questions regarded the demographics, health histories, and indoor/outdoor environments in which their dogs live and play. Responses for dogs with primary hypoadrenocorticism were compared to those without the disease using univariate and multivariate logistic regression models.

RESULTS

Five thousand forty-seven responses (358 cases, 4689 controls) met initial inclusion criteria. Significant associations with modest effect size were found for community type, ingestion of canned food, and use of lawn fertilizer in some analysis models. Reproductive (spay/neuter) status exhibited the strongest association with high effect size across all models with adjusted odds ratio (OR) 2.5 (95% confidence interval [CI], 1.4-4.5; P = .003) for spayed females and 6.0 (95% CI, 2.6-13.9; P < .001) for neutered males.

CONCLUSIONS AND CLINICAL IMPORTANCE

The large effect size for reproductive status reflects its high potential clinical relevance, whereas modest effect sizes for other environmental variables suggest lower potential clinical relevance. These findings are associations and do not necessarily imply causation. Before any actionable recommendations are warranted, additional evidence regarding biological mechanisms is needed.

Genetic characterization of Addison's disease in Bearded Collies

BACKGROUND

Primary hypoadrenocorticism (or Addison's disease, AD) is an autoimmune disease that results in destruction of the adrenal cortex and consequent adrenal insufficiency. The disease has been described in purebred and mixed breed dogs, although some breeds, including the Bearded Collie, are at increased risk for AD. Candidate gene approaches have yielded few associations that appear to be breed-specific. A single other genome-wide association study reported no significant regions of association for AD in Standard Poodles. The present study aimed to identify genomic regions of association for canine AD in Bearded Collies.

RESULTS

Our study consists of the first genome-wide association analysis to identify a genome-wide significant region of association with canine AD (CFA18). Peaks of suggestive association were also noted on chromosomes 11, 16 and 29. Logistic regression analysis supported an additive effect of risk genotypes at these smaller effect loci on the probability of disease associated with carrying a risk genotype on CFA18. Potential candidate genes involved in adrenal steroidogenesis, regulation of immune responses and/or inflammation were identified within the associated regions of chromosomes 11 and 16. The gene-poor regions of chromosomes 18 and 29 may, however, harbor regulatory sequences that can modulate gene expression and contribute to disease susceptibility.

CONCLUSION

Our findings support the polygenic and complex nature of canine AD and identified a strongly associated locus on CFA18 that, when combined with three other smaller effect loci, was predictive of disease. The results offer progress in the identification of susceptibility loci for canine AD in the Bearded Collie. Further studies are needed to confirm association with the suggested candidate genes and identify actual causative mutations involved with AD susceptibility in this breed.

Randomised clinical non-inferiority trial comparing two formulations of desoxycortone pivalate for the treatment of canine primary hypoadrenocorticism

BACKGROUND

This clinical trial compared two formulations of desoxycortone pivalate (DOCP) for treating the mineralocorticoid deficit in dogs with primary hypoadrenocorticism (PH).

METHODS

At veterinary clinics in the USA and France, dogs with PH (n=152) were randomised (3:1) to receive approximately monthly treatments with either the test product, Zycortal (Dechra), administered subcutaneously (n=113), or the control product, Percorten-V (Novartis Animal Health), administered intramuscularly (n=39), both at an initial dose of 2.2 mg/kg DOCP. Treatment administrators were unblinded; veterinarians assessing clinical signs were blinded; owners were blinded until at least day 90, the primary end point. Veterinarians assessed treatment outcome based on all of the following: clinical signs; sodium concentrations; potassium concentrations. Dogs received concurrent glucocorticoid therapy throughout the trial. Non-inferiority was assessed using a generalised linear mixed model to compare success rates between groups.

RESULTS

Success rates at day 90 were similar between groups (per-protocol population at day 90: Zycortal 87/101, 86.2 per cent, Percorten-V 29/34, 85.1 per cent). Zycortal was non-inferior to Percorten-V as the upper limit of the 95 per cent CI for the difference between groups was 13.6 per cent. Polydipsia and polyuria were the most common clinical observations.

CONCLUSION

Both products, in combination with glucocorticoid therapy, were safe and effective in treating PH.

Machine learning algorithm as a diagnostic tool for hypoadrenocorticism in dogs

Canine hypoadrenocorticism (CHA) is a life-threatening condition that affects approximately 3 of 1,000 dogs. It has a wide array of clinical signs and is known to mimic other disease processes, including kidney and gastrointestinal diseases, creating a diagnostic challenge. Because CHA can be fatal if not appropriately treated, there is risk to the patient if the condition is not diagnosed. However, the prognosis is excellent with appropriate therapy. A major hurdle to diagnosing CHA is the lack of awareness and low index of suspicion. Once suspected, the application and interpretation of conclusive diagnostic tests is relatively straight forward. In this study, machine learning methods were employed to aid in the diagnosis of CHA using routinely collected screening diagnostics (complete blood count and serum chemistry panel). These data were collected for 908 control dogs (suspected to have CHA, but disease ruled out) and 133 dogs with confirmed CHA. A boosted tree algorithm (AdaBoost) was trained with 80% of the collected data, and 20% was then utilized as test data to assess performance. Algorithm learning was demonstrated as the training set was increased from 0 to 600 dogs. The developed algorithm model has a sensitivity of 96.3% (95% CI, 81.7%-99.8%), specificity of 97.2% (95% CI, 93.7%-98.8%), and an area under the receiver operator characteristic curve of 0.994 (95% CI, 0.984-0.999), and it outperforms other screening methods including logistic regression analysis. An easy-to-use graphical interface allows the practitioner to easily implement this technology to screen for CHA leading to improved outcomes for patients and owners.

Prednisolone dosages in Addisonian dogs after integration of ACTH measurement into treatment surveillance

OBJECTIVE

To examine the prednisolone and fludrocortisone dosages in dogs with primary hypoadrenocorticism after integrating endogenous ACTH (eACTH) determination into the surveillance regimen.

MATERIALS AND METHODS

The local electronic medical records database was searched for dogs with primary hypoadrenocorticism and a complete follow-up including routine eACTH measurements until stabilisation. Dogs were considered stable if they showed no signs of glucocorticoid deficiency or excess, sodium and potassium were within the laboratory reference limits and no change of prednisolone and/or fludrocortisone dosage was recommended by the clinician. To avoid subclinical glucocorticoid overreplacement prednisolone was routinely reduced in case of eACTH concentrations below the detection limit of the assay.

RESULTS

Thirteen client-owned dogs were eligible for inclusion in the study. Stabilisation was achieved after a median (range) of 14 (1-36) months and 4 (2-9) visits. After exclusion of two patients that did not need additional glucocorticoids, the prednisolone dosage was 0.06 (0.02-0.26) mg/kg/day and 9.1 times lower than the starting dose. No correlation was identified between prednisolone dosage in mg/kg/day and bodyweight (r_SP = -0.369, p = 0.215). The final fludrocortisone dose was 0.022 (0.013-0.036) mg/kg/day. The median (range) survival time of the dogs that had died during the study period (n = 6) and all dogs was 74.5 (62-98) months and 71 (18-104) months, respectively.

CONCLUSION AND CLINICAL RELEVANCE

The integration of eACTH measurement into treatment surveillance helps to optimise glucocorticoid replacement therapy. It supports treatment recommendations and is a particular aid in dogs with ambiguous clinical signs. The results suggest that most dogs on fludrocortisone substitution therapy benefit from additional very low dose prednisolone.

Prevalence and clinical features of hypoadrenocorticism in Great Pyrenees dogs in a referred population: 11 cases

Naturally occurring hypoadrenocorticism (Addison's disease) is uncommon, with an estimated prevalence in the canine population between 0.06% and 0.28%. This retrospective study evaluated the prevalence and clinical features of hypoadrenocorticism in Great Pyrenees (GP) dogs presented to the Centre Hospitalier Universitaire Vétérinaire of the University of Montreal between March 2005 and October 2014. During this period, 100 dogs were diagnosed with hypoadrenocorticism, representing 0.38% [95% confidence interval (CI): 0.26% to 0.5%] of the canine population studied. The highest prevalence was observed in GP (9.73%, 95% CI: 9.12% to 10.35%, P < 0.0001), followed by West Highland white terriers (4.66%, 95% CI: 4.24% to 5.09%, P < 0.0001), Great Danes (1.87%, 95% CI: 1.6% to 2.14%, P < 0.0001), standard poodles (1.76%, 95% CI: 1.5% to 2.02%, P = 0.0001), Saint Bernards (1.72%, 95% CI: 1.47% to 1.98%, P = 0.018), and Jack Russell terriers (1.48%, 95% CI: 1.24% to 1.72%, P = 0.003). Although most clinical features were nonspecific, Great Pyrenees dogs were more frequently presented with anemia, azotemia, and eosinophilia, or with hypotension and cachexia compared with dogs of other breeds.

Autoantibodies against Cytochrome P450 Side-Chain Cleavage Enzyme in Dogs (Canis lupus familiaris) Affected with Hypoadrenocorticism (Addison's Disease)

Canine hypoadrenocorticism likely arises from immune-mediated destruction of adrenocortical tissue, leading to glucocorticoid and mineralocorticoid deficiency. In humans with autoimmune Addison's disease (AAD) or autoimmune polyendocrine syndrome (APS), circulating autoantibodies have been demonstrated against enzymes associated with adrenal steroid synthesis. The current study investigates autoantibodies against steroid synthesis enzymes in dogs with spontaneous hypoadrenocorticism. Coding regions of canine CYP21A2 (21-hydroxylase; 21-OH), CYP17A1 (17-hydroxylase; 17-OH), CYP11A1 (P450 side-chain cleavage enzyme; P450scc) and HSD3B2 (3β hydroxysteroid dehydrogenase; 3βHSD) were amplified, cloned and expressed as 35S-methionine radiolabelled recombinant protein. In a pilot study, serum samples from 20 dogs with hypoadrenocorticism and four unaffected control dogs were screened by radio-immunoprecipitation assay. There was no evidence of reactivity against 21-OH, 17-OH or 3βHSD, but five dogs with hypoadrenocorticism showed immunoreactivity to P450scc compared with controls. Serum samples were subsequently obtained from 213 dogs diagnosed with hypoadrenocorticism and 110 dogs from a hospital control population. Thirty control dogs were randomly selected to establish a threshold for antibody positivity (mean + 3 × standard deviation). Dogs with hypoadrenocorticism were more likely to be P450scc autoantibody positive than hospital controls (24% vs. 1.2%, respectively; p = 0.0016). Sex was significantly associated with the presence of P450scc autoantibodies in the case population, with 30% of females testing positive compared with 17% of males (p = 0.037). Significant associations with breed (p = 0.015) and DLA-type (DQA1*006:01 allele; p = 0.017) were also found. This cross-sectional study indicates that P450scc autoantibodies are present in a proportion of dogs affected with hypoadrenocorticism.

A suspected case of Addison's disease in cattle

A 4.75-year old Simmental cow was presented with symptoms of colic and ileus. The clinical signs and blood analysis resulted in the diagnosis of suspected primary hypoadrenocorticism (Addison's disease). Although Addison's disease has been frequently described in other domestic mammals, to our knowledge, this disease has not previously been reported in cattle.

[Acute haemorrhagic diarrhoea as a presenting sign in a dog with primary hypoadrenocorticism]

A 7-year-old male castrated mixed breed dog was presented because of acute haemorrhagic vomiting and watery haemorrhagic diarrhoea. According to clinical signs, nonspecific clinicopathological abnormalities, normal electrolytes and a rapid improvement with fluid therapy, haemorrhagic gastroenteritis (HGE) was suspected. One month later the dog was represented with weakness and electrolyte changes characteristic for typical hypoadrenocorticism (hyperkalaemia and hyponatraemia) were found. The tentative diagnosis was confirmed using an ACTH stimulation test. This case report highlights that dogs with hypoadrenocorticism may be presented with acute haemorrhagic diarrhoea. Electrolyte changes characteristic for hypoadrenocorticism may not be present in case of gastrointestinal potassium loss because of vomiting and diarrhoea. To rule out hypoadrenocorticism, a basal cortisol measurement should be performed in every dog with acute haemorrhagic diarrhoea of unknown cause.

Correlation of inflammation with adrenocortical atrophy in canine adrenalitis

Hypoadrenocorticism or Addison's disease (AD) is a functional disorder in which insufficient mineralocorticoid and glucocorticoid hormones are produced by the adrenal cortex. Human AD is usually attributed to lymphoplasmacytic adrenalitis with autoimmune destruction of the adrenal cortex. Lymphoplasmacytic adrenalitis is also reported in some descriptions of canine AD; however, the histological aspects of adrenalitis or adrenocortical atrophy have not been well characterized because microscopical examination is not required for diagnosis of AD. In this study, sections of adrenal glands from 33 dogs with adrenalitis were compared with those of 37 dogs without adrenal lesions. The affected dogs were classified clinically as having AD (n = 3), being suspected of having AD (n = 17), not having AD (n = 11) or were unclassified (n = 2). The adrenal inflammation was lymphoplasmacytic in 17 dogs, lymphocytic in four, lymphohistiocytic in one, granulomatous in three and neutrophilic in eight cases. Adrenal glands from control dogs lacked leucocyte infiltration and had a cortical to medullary area ratio of 1.1-7.2. All three dogs with AD, 8/17 dogs with suspected AD and 1/11 dogs without AD had a cortical to medullary area ratio <1.1. Because the area ratio was correlated (r = 0.94) with a linear cortical to medullary thickness ratio, a thickness ratio <1.1 could also indicate severe adrenocortical atrophy. Severe adrenocortical atrophy was associated typically with lymphoplasmacytic infiltration and nearly complete loss of cortical cells; however, the zona glomerulosa was partially spared in three dogs with lymphoplasmacytic adrenalitis and severe cortical atrophy. In contrast, non-lymphoid inflammation was generally part of systemic disease, multifocal and was unaccompanied by severe adrenocortical atrophy.

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.

Canine hypoadrenocorticism: part II

Dogs with chronic, vague gastrointestinal signs and those with signs and laboratory abnormalities suggestive of an Addisonian crisis should be tested for hypoadrenocorticism. A previous article (Part I; Can Vet J 2009;50:63-69) discussed the etiology, pathophysiology, clinical signs, and diagnostic abnormalities found in these patients. The present article discusses definitive diagnosis and treatment for both the acute and the chronic Addisonian patient. Expedient treatment remains the cornerstone of management for these patients, particularly those in the former category. The long-term prognosis is excellent for these patients, given well-educated, committed, and vigilant owners.

Canine hypoadrenocorticism: part I

Hypoadrenocorticism (Addison's disease) has been referred to as "the great pretender," due to its ability to mimic other common diseases in the dog and thereby represent a diagnostic challenge. Naturally occurring hypoadrenocorticism is an uncommon canine disease. Young, female dogs are overrepresented. Hypoadrenocorticism typically results from immune-mediated destruction of all adrenocortical layers, resulting in deficiencies of min-eralocorticoids (aldosterone) and glucocorticoids (cortisol). A small number of dogs suffer from glucocorticoid deficiency only. Dogs suffering from hypoadrenocorticism may present in a variety of conditions, from a mildly ill dog to a shocky and recumbent dog. This review discusses etiology, pathophysiology, history, physical examination findings, and diagnostic findings in the Addisonian patient. A follow-up article (Part II) will discuss the definitive diagnosis and management strategies for these patients.

Eucoleus aerophilus respiratory infection in a dog with Addison's disease

A 4-year-old, standard poodle was presented to the Ontario Veterinary College for a 3-week history of a moist, productive cough that was first noted while boarding at a kennel. Bronchoalveolar lavage revealed numerous ova identified as Eucoleus aerophilus, previously known as Capillaria aerophila. Clinical signs resolved following treatment with fenbendazole.

Understanding the genetics of autoimmune disease: two loci that regulate late onset Addison's disease in Portuguese Water Dogs

Addison's disease, an immune-mediated disorder caused by destruction of the adrenal glands, is a rare disorder of Western European populations. Studies indicate that the disorder is polygenic in nature, involving specific alleles of the CTLA-4, DRB1*04 and DQ, Cyp27B1, VDR and MIC-A and -B loci. A similar immune form of Addison's disease occurs in several breeds of domestic dog, with frequencies ranging from 1.5 to 9.0%. The high frequency of the disease in domestic dog breeds likely reflects the small number of founders associated with many breeds, subsequent inbreeding, and the frequent use of popular sires. The Portuguese Water Dog (PWD) is a significantly affected breed. An analysis of 11,384 PWDs surveyed between 1985 and 1996 suggests a breed-specific disease incidence of 1.5%. As with humans, the disease is typically of late onset. This study involves a genetic comparison of Addison's disease in the PWD to the analogous disease in humans. The study is facilitated by the existence of complete pedigrees and a relatively high degree of inbreeding among PWDs. The breed originated from 31 founders, with 10 animals responsible for 90% of the current gene pool. We describe, specifically, the identification of two disease-associated loci, on Canis familiaris (CFA) chromosomes CFA12 and 37, which are syntenic with the human DRB1 histocompatibility locus alleles HLA-DRB1*04 and DRB1*0301, and to a locus for immunosuppression syntenic with CTLA-4. Strong similarities exist therefore in the complex genetic background of Addison's disease in humans and in the PWD. With the completion of the canine and human genome sequence, the purebred dog is set to become an important comparative model for Addison's as well as other human immune disorders.

Genetic evaluation of Addison's disease in the Portuguese Water Dog

BACKGROUND

Addison's disease, also known as hypoadrenocorticism, has been reported in many individual dogs, although some breeds exhibit a greater incidence than the population as a whole. Addison's is presumed to be an autoimmune mediated hereditary defect but the mode of inheritance remains unclear. In particular, the heritability and mode of inheritance have not been defined for the Portuguese Water Dog although Addison's is known to be prevalent in the breed.

RESULTS

The analyses present clear evidence that establishes Addison's disease as an inherited disorder in the Portuguese Water Dog with an estimate of heritability of 0.49 (+/- 0.16); there were no differences in risk for disease across sexes (p > 0.49). Further, the complex segregation analysis provides suggestive evidence that Addison's disease in the Portuguese Water Dog is inherited under the control of a single, autosomal recessive locus.

CONCLUSION

The high heritability and mode of inheritance of Addison's disease in the Portuguese Water Dog should enable the detection of segregating markers in a genome-wide scan and the identification of a locus linked to Addison's. Though the confirmation of Addison's disease as an autosomal recessive disorder must wait until the gene is identified, breeders of these dogs may wish to keep the present findings in mind as they plan their breeding programs to select against producing affected dogs.

Hypoadrenocorticism in a cat

Primary hypoadrenocorticism was diagnosed in an eight-year-old neutered male cat. The predominant presenting complaint was dysphagia. Other historical signs included lethargy, weight loss, polydipsia, polyuria, muscle weakness and occasional vomiting. The signs had waxed and waned over the two months before presentation and had improved when the cat was treated with enrofloxacin and prednisolone by the referring veterinarian. On referral, dehydration, depression and poor bodily condition were found on physical examination. Results of initial laboratory tests revealed mild anaemia, hyperkalaemia, hyponatraemia, hypochloraemia and elevations in serum creatinine and creatine kinase. The diagnosis of primary adrenocortical insufficiency was established on the basis of results of an adrenocorticotropic hormone (ACTH) stimulation test and endogenous plasma ACTH determination. Initial therapy for hypoadrenocorticism included intravenous administration of 0.9 per cent saline and dexamethasone, and oral fludrocortisone acetate. Within one week the cat was clinically normal and two years later was still alive and well on fludrocortisone acetate treatment only.

A case of feline primary hypoadrenocorticism

A 2-year-old entire female British Shorthair cat was referred to the University of Bristol for investigation of lethargy, weakness, constipation and hypothermia. Clinical examination revealed a profoundly weak, hypovolaemic and hypothermic cat. Serum biochemistry revealed hyponatraemia, hyperkalaemia and hyperphosphataemia and the urine was isosthenuric. Lack of response to exogenous adrenocorticotrophic hormone confirmed a diagnosis of hypoadrenocorticism. Treatment consisted initially of intravenous fluid therapy and subsequently a combination of fludrocortisone and prednisolone per os. At follow-up, 20 months after the initial diagnosis the cat remained stable and free of clinical signs.

Hypocortisolaemia in a Labrador retriever

A four-year-old Labrador retriever was presented with lethargy and exercise intolerance. Clinical examination was unremarkable. A subnormal cortisol response to adrenocorticotrophin hormone (ACTH) was demonstrated (plasma cortisol concentrations before and after administration of ACTH were both below the detection limit of the assay) but plasma aldosterone concentrations were within the normal range. Endogenous plasma ACTH concentrations were high, indicating primary adrenocortical disease. Following glucocorticoid supplementation at a replacement dose (prednisolone 0.1 mg/kg) the dog made a full clinical recovery.

Duplex Doppler measurements of renal blood flow in a dog with Addison's disease

Abnormal intrarenal flow in a seven-year old female Tibetan terrier with Addison's disease was demonstrated by duplex Doppler examination. Abnormal flow may reflect renal vasoconstriction due to increased activity of the renin-angiotensin system. Although not pathognomonic, an increased resistive index (> 0.70) in an otherwise ultrasonographically normal kidney can be due to Addison's disease and the technique may prove valuable as a quick non-invasive tool in the management of this disease.

Atypical Addison's disease in the dog: a retrospective survey of 14 cases

Fourteen dogs diagnosed with Addison's disease and having atypical serum electrolyte levels are described. Seventy-eight percent were female, and most showed signs of inappetence, weakness, or vomiting. Ninety-three percent of the cases had either hyponatremia without hyperkalemia or normal serum electrolyte concentrations. Hemogram features were variable and were not useful in suggesting a diagnosis of hypoadrenocorticism. The results of this study show that normal or mild serum electrolyte changes in a dog with clinical signs compatible with Addison's disease should not exclude this diagnosis from consideration. Definitive diagnosis depends on the demonstration of inadequate adrenocortical response to adrenocorticotropic hormone (ACTH) stimulation.

Desoxycorticosterone pivalate in the management of canine primary hypoadrenocorticism

Primary hypoadrenocorticism in dogs may be poorly responsive to oral fluorocortisone treatment. Desoxycorticosterone pivalate is a suggested alternative treatment in these and all other cases of hypoadrenocorticism. Primary hypoadrenocorticism was diagnosed in a 3-year-old Cocker Spaniel bitch. Treatment with oral fluorocortisone at a dose rate of 0.13 mg 5 kg-1 d-1 was ineffective at maintaining serum electrolyte concentrations within normal limits. Administration of DOCP at a dose of 1.6-2.2 mg kg-1 intramuscularly every 28 d over a 5-year period, successfully maintained normal serum sodium and potassium concentrations. Side-effects encountered were minimal and were dose- or disease-related.

Mitotane treatment of 32 dogs with cortisol-secreting adrenocortical neoplasms

Thirty-two dogs with hyperadrenocorticism caused by cortisol-secreting adrenocortical neoplasia were treated with mitotane at an initial daily induction dosage of 27.5 to 75.0 mg/kg of body weight (mean, 46.3 mg/kg) for 10 to 14 days. All dogs received daily maintenance glucocorticoid supplementation during the induction period. After 2 weeks, the ACTH-stimulated serum cortisol concentration had decreased to within or below the reference range for baseline cortisol concentration in 18 (56.3%) of the 32 dogs; the remaining 14 (43.7%) still responded to ACTH administration with serum cortisol concentrations above the reference range. In these 14 dogs, mitotane was continued at a higher daily dosage (mean, 60.7 mg/kg) for an additional 1 to 9 weeks. Serum cortisol concentration subsequently fell within or below the reference range for baseline cortisol concentration in all but 1 dog. In 30 of the 32 dogs, mitotane was continued at an initial mean maintenance dosage of 101.6 mg/kg/wk, divided into 2 to 5 doses. Twenty-two dogs received prednisone daily (0.2 mg/kg) throughout the maintenance period. One or more relapses occurred in 19 (63%) of the 30 dogs. In dogs with relapse, the mean maintenance mitotane dosage was increased from 98.1 mg/kg/wk to a high of 212.4 mg/kg/wk. After a mean maintenance treatment time of 13.2 months, final mean maintenance dosage required in the 30 dogs ranged from 35.3 to 1,273 mg/kg/wk. Adverse effects were seen in 19 (59.4%) of the 32 dogs as a result of a drug toxicosis associated with high-dosage administration of mitotane, low serum cortisol concentration, or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Skin diseases of old dogs and cats

The ageing process tends to predispose dogs and cats to certain skin diseases. Impaired immunosurveillance is believed to render the animals more susceptible to neoplasia which can affect any organ including the skin. Endocrinopathies are also more common in older animals. There are some diseases of internal organs which can affect the skin, and some of these tend to occur with increased frequency in old animals. Finally, seborrhoeic diseases are either more common in older animals, or become increasingly severe with age.

Primary hypoadrenocorticism in ten cats

Primary hypoadrenocorticism was diagnosed in ten young to middle-aged cats of mixed breeding. Five of the cats were male, and five were female. Historic signs included lethargy (n = 10), anorexia (n = 10), weight loss (n = 9), vomiting (n = 4), and polyuria (n = 3). Dehydration (n = 9), hypothermia (n = 8), prolonged capillary refill time (n = 5), weak pulse (n = 5), collapse (n = 3), and sinus bradycardia (n = 2) were found on physical examination. Results of initial laboratory tests revealed anemia (n = 3), absolute lymphocytosis (n = 2), absolute eosinophilia (n = 1), and azotemia and hyperphosphatemia (n = 10). Serum electrolyte changes included hyponatremia (n = 10), hyperkalemia (n = 9), hypochloremia (n = 9), and hypercalcemia (n = 1). The diagnosis of primary adrenocortical insufficiency was established on the basis of results of adrenocorticotropic hormone (ACTH) stimulation tests (n = 10) and endogenous plasma ACTH determinations (n = 7). Initial therapy for hypoadrenocorticism included intravenous administration of 0.9% saline and dexamethasone and intramuscular administration of desoxycorticosterone acetate in oil. Three cats were euthanatized shortly after diagnosis because of poor clinical response. Results of necropsy examination were unremarkable except for complete destruction of both adrenal cortices. Seven cats were treated chronically with oral prednisone or intramuscular methylprednisolone acetate for glucocorticoid supplementation and with oral fludrocortisone acetate or intramuscular injections of repository desoxycorticosterone pivalate for mineralocorticoid replacement. One cat died after 47 days of therapy from unknown causes; the other six cats are still alive and well after 3 to 70 months of treatment.

Addison's disease in a puppy

Low serum cortisol levels in a young puppy, following adrenocorticotrophic hormone (ACTH) stimulation, were used to establish a clinical diagnosis of Addison's disease. This was likely to have been congenital although studies of adrenocortical function in close relatives showed no evidence of a genetic origin for the condition. Autoantibody to canine adrenal tissue was not present. Further investigations are necessary to establish the role of autoantibody in canine hypoadrenocorticism. The diagnosis of primary adrenocortical hypoplasia was confirmed at post mortem examination.

Diseases of the adrenal cortex of dogs and cats

The most common cause of hypoadrenocorticism in dogs is idiopathic immune-mediated destruction of the adrenal cortex. Other causes include anterior pituitary insufficiency, pituitary or adrenal neoplasia, acute withdrawal of exogenous corticosteroids, and mitotane toxicity. Females are affected more often than males; only 1 feline case has been documented. Animals 2-5 years old are most commonly affected. Clinical signs include lethargy, weakness, weight loss, anorexia, vomiting, diarrhea and bradycardia. Hematologic and biochemical changes can include eosinophilia, lymphocytosis, anemia, hyperkalemia, hyponatremia and hypercalcemia. Diagnosis is by finding negligible resting levels of plasma cortisol and no response to ACTH administration, and a serum Na:K ratio of 20:1 or less. Treatment involves restoring fluid volume, correcting acidosis, and supplementing salt and glucocorticoids. Daily oral use of prednisone at 0.05 mg/kg can safely maintain most affected dogs. Some dogs only require glucocorticoids in stressful situations. Iatrogenic secondary adrenocortical insufficiency (iatrogenic Cushing's disease) may result from a single injection of long-acting glucocorticoids or from long-term use. Clinical signs are the same as for natural hyperadrenocorticism, but endogenous cortisol release is suppressed. Treatment is gradual withdrawal of the offending glucocorticoid and elimination of the cause that initially prompted glucocorticoid therapy.

Hypercalcemia associated with hypoadrenocorticism in sixteen dogs

During a 3-year-period, hypercalcemia was found in 16 (28%) of 62 dogs with hypoadrenocorticism. Thirteen of the dogs were hypercalcemic at the time of diagnosis, whereas hypercalcemia developed at relapse during maintenance corticosteroid therapy in 3 dogs. The severity of hypercalcemia correlated with the severity of hypoadrenocorticism. Clinical signs and biochemical disturbances were more severe and mean calcium concentration was significantly higher in the dogs that were hypercalcemic at time of diagnosis than in the dogs that became hypercalcemic while on therapy. In all dogs, the high calcium concentration promptly and completely resolved with adequate corticosteroid replacement therapy.

Hypoadrenocorticism following therapy with o,p-DDD for hyperadrenocorticism in four dogs

Hypoadrenocorticism developed in 4 of 26 dogs treated with mitotane (o,p-DDD) for hyperadrenocorticism. Evidence of the hypoadrenocorticism was detected from 2-8 weeks after the beginning of weekly or bimonthly maintenance o,p-DDD therapy. The adversely affected dogs had hyponatremia plus hyperkalemia, and 3 of the 4 had severely diminished plasma cortisol concentrations at rest or after stimulation with ACTH given IM. One dog did not have detectable plasma aldosterone concentrations before or after ACTH administration. Clinically, 3 of the 4 dogs responded well to mineralocorticoid replacement. Electrolyte determinations after replacement therapy in 1 dog documented normal serum sodium and potassium concentrations. One dog died despite therapy and was determined to have adrenocortical destruction.

Canine hypoadrenocorticism: report of 37 cases and review of 39 previously reported cases

Thirty-seven cases of canine hypoadrenocorticism were compared with 39 previously reported cases. The 2 series were compared because it was believed that a study of 37 consecutive cases diagnosed at 1 institution (Michigan State University) and compiled by 1 group of veterinarians would yield data that were more representative of the disease than multiple cases from various institutions. Age, sex, and breed data were similar in both series. The frequency of anorexia, vomiting, depression, and the mean values for the clinicopathologic data were similar for both series except for blood glucose concentration (P less than 0.025). The Michigan State University series was different in that it had a lower frequency of eunatremia, increased plasma total solids, and hypoglycemia but a higher frequency of lymphocytosis, lymphopenia, hyponatremia, hyperglycemia, and hypercalcemia. Further, 3 dogs in the Michigan State University series had azotemia plus near isosthenuric urine, suggesting renal disease, but they seemingly responded to therapy for hypoadrenocorticism. Only 1 such case was identified in the literature. Finally, we detected fewer instances of P waves not being evident in lead II of an electrocardiogram.