Longitudinal assessment of thyroid function in dogs with hypoadrenocorticism: Clinical outcomes and prevalence of autoantibodies

BACKGROUND

Knowledge about primary hypoadrenocorticism coexisting with immune-mediated thyroiditis (Schmidt's syndrome) in dogs is limited.

OBJECTIVE

To evaluate thyroid function in dogs with naturally occurring hypoadrenocorticism before and during treatment.

ANIMALS

Sixty-six client-owned dogs.

METHODS

Measurement of canine thyroid stimulating hormone (cTSH), total thyroxine (T4), free thyroxine, and autoantibodies against thyroglobulin, T4, and total triiodothyronine.

RESULTS

Thirty-eight dogs were assessed before and 28 during treatment. Follow-up data were available for 24/38 and 17/28 dogs, with median follow-up duration of 3.8 years (range, <1.0-8.8 years) and 4 years (range, 1.1 weeks to 10.5 years), respectively. Canine thyroid stimulating hormone was above the reference range at the time of diagnosis of hypoadrenocorticism in 10 of 38 dogs but decreased into the reference range in 7 for which follow-up data was available. Hypothyroidism was confirmed in 5 dogs at a median age of 11 years (range, 7-15 years). In 4 dogs, the condition was diagnosed after a median treatment duration of 5.75 years (range, 2.6-10 years), while in 1 dog, the diagnosis was made concurrently. One dog had detectable thyroid autoantibodies.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypothyroidism occurs as a rare concurrent condition in dogs with hypoadrenocorticism, potentially at any phase of treatment. Close monitoring of cTSH levels in these dogs could be beneficial, as early changes might indicate the onset of hypothyroidism. The low prevalence of detectable thyroid autoantibodies suggests that nonimmune mechanisms might contribute to thyroid dysfunction.

Hypothalamic-pituitary-adrenal axis recovery after intermediate-acting glucocorticoid treatment in client-owned dogs

BACKGROUND

In dogs, duration of hypothalamic-pituitary-adrenal (HPA) axis suppression after systemic glucocorticoid treatment is reported to vary from a few days to up to 7 weeks after glucocorticoid discontinuation. These data are derived mainly from experimental studies in healthy dogs and not from animals with spontaneous disease.

HYPOTHESIS AND OBJECTIVE

To determine the timeline for recovery of the HPA axis in a group of ill dogs treated with intermediate-acting glucocorticoids (IAGCs).

ANIMALS

Twenty client-owned dogs that received IAGC for at least 1 week.

METHODS

Single-center prospective observational study. An ACTH stimulation test, endogenous ACTH concentration, serum biochemistry profile, and urinalysis were performed at T0 (2-6 days after IAGC discontinuation) and then every 2 weeks (eg, T1, T2, T3) until HPA axis recovery was documented (post-ACTH cortisol concentration > 6 μg/dL).

RESULTS

The median time of HPA axis recovery was 3 days (range, 2-133 days). Eleven of 20 dogs showed recovery of the HPA axis at T0, 6/20 at T1, and 1 dog each at T2, T5, and T9. Dose and duration of treatment were not correlated with timing of HPA axis recovery. Activities of ALT and ALP were significantly correlated with the post-ACTH cortisol concentration (rs = -0.34, P = .03; rs = -0.31, P = .05). Endogenous ACTH concentration was significantly correlated with pre (r = 0.72; P < .0001) and post-ACTH cortisol concentrations (r = 0.35; P = .02). The timing of HPA axis recovery of the dogs undergoing an alternate-day tapering dose was not different compared to dogs that did not (3.5 vs 3 days, P = .89).

CONCLUSION AND CLINICAL IMPORTANCE

Most dogs experienced HPA axis recovery within a few days after IAGC discontinuation. However, 2/20 dogs required >8 weeks.

[Polyendocrine syndromes in dogs]

The autoimmune polyendocrine syndrome (APS) refers to a combination of autoimmune endocrine disorders. It is rarely described in dogs. The most common combinations are hypoadrenocorticism and hypothyroidism, followed by diabetes mellitus, and less often hypoparathyroidism and orchitis. The diagnosis of the APS is based on the diagnosis of each endocrinopathy, as is the therapy, which involves the substitution of deficient hormones. If a patient was previously stable under treatment and is showing further signs (e.g. polyuria, polydipsia, or weight loss), the development of additional endocrinopathies like hypoadrenocorticism or diabetes mellitus should be considered. The diagnosis of the initially diagnosed endocrinopathy should also be critically questioned. This article summarizes some cases of our own animal hospital and selected cases published in the available literature.

Case report: Central-pituitary hypothyroidism concurrent with hyperadrenocorticism without pituitary macroadenoma in a Miniature Schnauzer dog

Multiple endocrine disorders are uncommon in veterinary medicine, and the disease combination is usually related to hypercortisolism or autoimmunity. Central-pituitary hypothyroidism, also refer to secondary hypothyroidism, can be caused by hypercortisolemic conditions and is well-recognized in human medicine. However, central hypothyroidism, including pituitary hypothyroidism, concurrent with hyperadrenocorticism, is rarely reported in veterinary medicine. A 7-year-old, intact female Miniature Schnauzer presented with generalized alopecia, scale, and pruritus and was diagnosed with superficial pyoderma and Malassezia dermatitis. Hormonal tests were performed, and the results indicated multiple endocrinopathies with a combination of non-adrenal dependent hyperadrenocorticism and central-pituitary hypothyroidism. Magnetic resonance imaging (7 T) and high-resolution research tomography positron emission tomography were performed to differentiate neuroendocrine tumors; however, no lesion was found in the hypothalamic to pituitary region. Hyperadrenocorticism was managed first to control endocrinopathy. After controlling hypercortisolism, a weak elevation of free thyroxine (T4) was revealed, whereas total T4 and thyroid-stimulating hormone (TSH) were still undetectable, and hypothyroidism management was added. About 9 months after the management, both endocrine diseases were well controlled, and clinical signs improved; however, serum TSH was unmeasured consistently. This case study describes a case of multiple endocrinopathies in a Miniature Schnauzer dog diagnosed with central-pituitary hypothyroidism concurrent with non-adrenal dependent hyperadrenocorticism without pituitary macroadenoma.

Histopathological evaluation of the adrenal glands in a cat with primary hypoadrenocorticism and multiple endocrine disease

Case summary

A 6-year-old male neutered domestic longhair cat was referred for investigation of weight loss, hyporexia, vomiting and diarrhoea. The cat was diagnosed with primary hypoadrenocorticism, exocrine pancreatic insufficiency, cobalamin deficiency and a chronic enteropathy, and started on therapeutic treatment. Diabetes mellitus developed 4.5 months later, and the cat was started on insulin therapy. The cat was euthanased 10 months following the diagnosis of hypoadrenocorticism due to the development of status epilepticus, which was not associated with glucose or electrolyte abnormalities. Histopathological assessment of the adrenal glands at post-mortem examination documented lymphoplasmacytic adrenalitis, with the lymphocytic population being predominant. Immunohistochemical staining classified the lymphocytic infiltrate as T-cell rich, supportive of the cat's hypoadrenocorticism being due to autoimmune disease.

Relevance and novel information

This case documents the novel use of immunohistochemical staining in combination with histopathology to further assess the adrenal glands in non-neoplastic-associated primary hypoadrenocorticism in a cat. This identified similar pathological changes to those previously described in dogs with autoimmune primary hypoadrenocorticism. Additionally, this is the first report of a cat with multiple endocrine disease that included primary hypoadrenocorticism and highlights that monitoring for the development of additional endocrine disease should be advised in these cases.

Breed distributions for diabetes mellitus and hypothyroidism in Norwegian dogs

BACKGROUND

Diabetes mellitus (DM) and hypothyroidism are common canine endocrinopathies. Both canine DM and primary hypothyroidism are assumed to originate from autoimmune destruction of the respective endocrine glands and have been associated with the major histocompatibility complex (MHC) gene region. This study aims to investigate breed distributions for DM and hypothyroidism in the Norwegian canine population by calculating odds ratios (OR) from two different comparator groups.

METHODS

Results from canine serum samples submitted from 2001 to 2018 to the Veterinary Clinical Pathology Laboratory (VCPL) at the Faculty of Veterinary Medicine, Norwegian University of Life Sciences for analysis of fructosamine and thyroid hormones in serum were used as cases in a retrospective bivariate analysis of canine breeds. The ORs were calculated as a measure of risk for the included breeds, where all the submitted blood samples to the VCPL and dogs registered in the Norwegian Kennel Club (NKK), the national organization for dog owners, were used as two comparator groups.

RESULTS

Significant differences in disease prevalence between breeds were discovered using both comparator groups. Australian terrier, Swedish lapphund, Samoyed, and Schipperke were at highest risk for DM. German Shepherd, Golden retriever, German pointing dog, and Collie presented as the breeds with lowest risk for DM. For hypothyroidism, Schnauzer, Eurasier, Dunker, and English setter were at highest risk for developing the disease. The breeds at lowest risk of developing hypothyroidism were Rottweiler, Dachshund, German shepherd, and Border collie. The results from the different comparator groups gave different ORs and ranks, but the breeds with highest and lowest odds showed the same susceptibility using both comparators.

CONCLUSIONS

These findings support that there are breeds more and less prone to develop DM and hypothyroidism. A strong genetic predisposition involved in the aetiology of these two diseases is therefore likely. Interestingly, there also appeared to be an inverse relationship of odds for the two diseases for some of the breeds since some breeds that had a high OR for DM or hypothyroidism had a lower OR for the other disease. This indicates that there may be different risk alleles/haplotypes for the two diseases. The possible aetiological relationship between canine DM and hypothyroidism should be further investigated.

Autoimmune polyendocrine syndrome with hypoadrenocorticism and diabetes mellitus in a dog: A rare case

BACKGROUND

Autoimmune polyendocrine syndrome, also called polyglandular autoimmune syndrome, is a rare immune-mediated disorder that involves various endocrine glands.

PURPOSE

To report autoimmune polyendocrine syndrome in a dog.

METHODS

A 9-year-old spayed female miniature poodle diagnosed with insulin-dependent diabetes mellitus emergently visited our clinic for anorexia, severe depression, and vomiting. Hyponatremia, hypochloridemia, and recurrent hypoglycaemia were found. Hypoadrenocorticism was diagnosed based on consistent clinical signs and repeated adrenocorticotropic hormone stimulation tests.

RESULTS

After injecting deoxycorticosterone pivalate and increasing the oral prednisolone dose, the patient's systemic condition improved.

CONCLUSIONS

To the best of our knowledge, this is the first case report of hypoadrenocorticism concurrent with diabetes mellitus in a dog. Furthermore, we would like to present the probability of an immune-mediated disorder with multiple organs involved, like type IV autoimmune polyendocrine syndrome in humans.

Genetics of canine diabetes mellitus part 1: Phenotypes of disease

This two-part article discusses the mechanisms by which genetic variation can influence the risk of complex diseases, with a focus on canine diabetes mellitus. In Part 1, presented here, the importance of accurate methods for classifying different types of diabetes will be discussed, since this underpins the selection of cases and controls for genetic studies. Part 2 will focus on our current understanding of the genes involved in diabetes risk, and the way in which new genome sequencing technologies are poised to reveal new diabetes genes in veterinary species.

Diabetes mellitus in dogs attending UK primary-care practices: frequency, risk factors and survival

Background

Diabetes mellitus (DM) is an important endocrine disorder of dogs. The objectives of this study were to estimate prevalence and incidence of DM in dogs, and to explore risk factors for DM and the survival of DM cases in primary-care clinics in the UK.

Results

A case-control study nested in the cohort of dogs (n = 480,469) aged ≥3 years presenting at 430 VetCompass clinics was used to identify risk factors for DM, using multivariable logistic regression. Overall 409 new and 863 pre-existing DM cases (total 1272) were identified in 2016, giving an apparent annual prevalence of 0.26% (95% confidence interval (CI): 0.25–0.28%), and an annual incidence risk of 0.09% (95%CI: 0.08–0.09%) in dogs aged ≥3 years. Factors associated with increased odds for DM diagnosis were all age categories > 8 years, female entire dogs (odds ratio (OR): 3.03, 95% CI 1.69–5.44, p < 0.001) and male neutered dogs (OR: 1.99, 95% CI 1.18–3.34, p = 0.010) compared to male entire dogs, Border Terriers (OR: 3.37, 95% CI 1.04–10.98, p = 0.043) and West Highland White Terriers (WHWT) (OR: 2.88, 95% CI 1.49–5.56, p = 0.002) compared to crossbreeds. Dogs that had received previous glucocorticoid treatment (OR: 2.19, 95% CI 1.02–4.70, p = 0.044) and those with concurrent conditions (documented obese, pancreatitis, hyperadrenocorticism) also had increased odds for DM diagnosis.

Cox regression modelling was used to evaluate factors associated with survival in the 409 incident DM cases in 2016. Increased hazard of death following diagnosis of DM was shown in dogs that were ≥ 10 years age, Cocker Spaniels (HR: 2.06, 95% CI 1.06–4.01, p = 0.034) compared to crossbreeds, had a blood glucose (BG) level at diagnosis > 40 mmol/L (HR: 2.73, 95% CI 1.35–5.55, p = 0.005) compared to < 20 mmol/L at diagnosis, or had received previous glucocorticoid treatment (HR: 1.86, 95% CI 1.21–2.86, p = 0.005). Dogs at reduced hazard of death included neutered dogs (HR: 0.58, 95% CI 0.42–0.79, p = 0.001), Border Collies (HR: 0.39, 95% CI 0.17–0.87, p = 0.022) and those starting insulin treatment (HR: 0.08 95% CI 0.05–0.12, p < 0.001).

Conclusions

Certain breeds and concurrent health conditions are associated with an increased risk of DM. In addition to certain signalment factors, a high BG level at diagnosis and prior glucocorticoid treatment were adversely associated with survival of dogs with DM.

Retrospective review of cataract surgery outcomes in Miniature Schnauzers

OBJECTIVE

Miniature Schnauzers commonly develop both inherited and diabetic cataracts. Miniature Schnauzers also often present with concurrent metabolic disease at the time of cataract surgery. The purpose of this study was to evaluate cataract surgery outcomes in Miniature Schnauzers.

MATERIALS AND METHODS

The Eye Care for Animals electronic medical record database (2012-2018) was searched for "phacoemulsification" and "Miniature Schnauzer." A minimum follow-up time of 1 year was required for inclusion in the study. Clinical history, pre- and postoperative bloodwork, postoperative treatments, and visual outcomes were reviewed in all cases.

RESULTS

Cataract surgery was performed on 67 patients and 124 eyes. 93.5% (116/124) of operated eyes were visual 1 year following cataract surgery. At the time of surgery, 79.1% were diabetic, 64.2% had hypercholesterolemia, 55.2% had hypertriglyceridemia, 16.4% had hyperadrenocorticism, and 9% had a history of pancreatitis. Dorzolamide was used postoperatively in 61.2% of patients, and its use was significantly associated with postoperative cholesterol levels above reference range. Lipemic aqueous occurred in 13.4% of patients.

CONCLUSIONS

Miniature Schnauzers presenting for cataract surgery are frequently affected by metabolic diseases and dyslipidemia; however, cataract surgery outcomes were not significantly affected during the study period. Dietary management, omega-3 fatty acid supplementation, and oral fibrates may reduce the incidence of lipemic aqueous in Miniature Schnauzers.

Canine hyperadrenocorticism associations with signalment, selected comorbidities and mortality within North American veterinary teaching hospitals

OBJECTIVE

To describe a large population of dogs with a diagnosis of hyperadrenocorticism at the time of death in North American veterinary teaching hospitals, and to identify comorbid conditions associated with hyperadrenocorticism.

MATERIALS AND METHODS

Retrospective cohort study of 1519 dogs with hyperadrenocorticism from a population of 70,574 dogs reported to the Veterinary Medical Database. Signalment, presence or absence of hyperadrenocorticism, aetiology of hyperadrenocorticism (if described), frequency of select comorbidities and causes of death were evaluated in dogs with and without hyperadrenocorticism.

RESULTS

Hyperadrenocorticism was more frequent in females. Neutering was associated with a minor, but significant, increase in the odds of hyperadrenocorticism. Hyperadrenocorticism was the presumed cause of death of 393 (25∙9%) of affected dogs. When aetiology was specified (527 dogs, corresponding to 34∙7% of the cases), pituitary-dependent hyperadrenocorticism [387 (73∙4%) out of 527 dogs] was more common than functional adrenocortical tumour [136 (25∙8%) out of 527 dogs). Hyperadrenocorticism was over-represented in certain expected (miniature poodle, dachshund) and unexpected (Irish setter, bassett hound) breeds compared with the population at large. Of the select comorbidities investigated, dogs with hyperadrenocorticism were at increased risk for concurrent diabetes mellitus, urinary tract infection, urolithiasis, hypertension, gall bladder mucocoele and thromboembolic disease compared with dogs without hyperadrenocorticism.

CLINICAL SIGNIFICANCE

Hyperadrenocorticism is significantly associated with certain comorbid conditions but is not a major cause of mortality in affected dogs. Documented patterns now provide targets for prospective clinical research.

Cardiogenic Pulmonary Edema in a Dog Following Initiation of Therapy for Concurrent Hypoadrenocorticism and Hypothyroidism

A 5 yr old intact female cocker spaniel dog weighing 7.8 kg was referred with anorexia, vomiting, and depression. At referral, the dog was diagnosed initially with typical hypoadrenocorticism, and 2 d later, concurrent primary hypothyroidism was detected. Hormonal replacement therapies, including fludrocortisone, prednisolone, and levothyroxine, were initiated, but a few days later the dog became abruptly tachypneic, and thoracic radiographs indicated the development of pulmonary edema. Echocardiography showed that there were abnormalities indicating impaired left ventricular function, although the heart valves were normal. Following treatment with pimobendan and furosemide, the pulmonary edema resolved. The dog had no recurrence of the clinical signs after 10 mo of follow-up, despite being off all cardiac medications; consequently, the cardiac failure was transient or reversible in this dog. The case report describes the stepwise diagnosis and successful treatment of cardiogenic pulmonary edema after initiation of hormonal replacement therapy for concurrent hypoadrenocorticism and hypothyroidism in a dog.

Hypothyroidism associated with acromegaly and insulin-resistant diabetes mellitus in a Samoyed

BACKGROUND

The aetiology of insulin resistance (IR) in naturally occurring canine hypothyroidism is poorly understood and likely multifactorial. Excess secretion of growth hormone (GH) by transdifferentiated pituitary cells may contribute to IR in some hypothyroid dogs, but although this has been demonstrated in experimental studies, it has not yet been documented in clinical cases.

CASE REPORT

A 4-year-old male entire Samoyed presented with an 8-month history of pedal hyperkeratosis and shifting lameness, which had been unresponsive to zinc supplementation, antibiotics and glucocorticoid therapy. The dog also exhibited exercise intolerance and polydipsia of 12 and 2 months duration, respectively. On physical examination, obesity, poor coat condition, widened interdental spaces and mild respiratory stridor were noted. Initial laboratory test results revealed concurrent hypothyroidism and diabetes mellitus (DM). Further investigations showed IR, GH excess and a paradoxical increase of GH following stimulation with thyrotropin-releasing hormone.

CONCLUSIONS

To the authors' knowledge, this is the first reported case that suggests that GH alterations may have clinical significance in naturally occurring hypothyroidism. Among other factors, hypothyroidism-induced GH excess should be considered as a possible cause of IR in patients suffering from hypothyroidism and concurrent DM. In such cases, DM may reverse with treatment of hypothyroidism, as was documented in this case.

Genetics of canine diabetes mellitus: are the diabetes susceptibility genes identified in humans involved in breed susceptibility to diabetes mellitus in dogs?

Diabetes mellitus is a common endocrinopathy in companion animals, characterised by hyperglycaemia, glycosuria and weight loss, resulting from an absolute or relative deficiency in the pancreatic hormone insulin. There are breed differences in susceptibility to diabetes mellitus in dogs, with the Samoyed breed being overrepresented, while Boxers are relatively absent in the UK population of diabetic dogs, suggesting that genetic factors play an important role in determining susceptibility to the disease. A number of genes, linked with susceptibility to diabetes mellitus in humans, are associated with an increased risk of diabetes mellitus in dogs, some of which appear to be relatively breed-specific. Diabetes mellitus in dogs has been associated with major histocompatibility complex (MHC) class II genes (dog leucocyte antigen; DLA), with similar haplotypes and genotypes being identified in the most susceptible breeds. A region containing a variable number of tandem repeats (VNTR) and several polymorphisms have been identified in the canine insulin gene, with some alleles associated with susceptibility or resistance to diabetes mellitus in a breed-specific manner. Polymorphisms in the canine CTLA4 promoter and in other immune response genes are associated with susceptibility to diabetes mellitus in a number of pedigree breeds. Genome wide association studies are currently underway that should shed further light on the genetic factors responsible for the breed profile seen in the diabetic dog population.