Hyperadrenocorticism in a dog due to ectopic secretion of adrenocorticotropic hormone

Transsphenoidal Surgery for Pituitary Tumors

Transsphenoidal surgery for the treatment of pituitary masses in cats and dogs has become a more established treatment over the last 2 decades. Although expert centers and surgeons that provide this service remain limited, the patient population presented for pituitary surgery increases with wider availability of advanced imaging, together with more challenging cases. In this review, the current state of hypophysectomy is described with future challenges and opportunities.

Frequency of low-dose dexamethasone suppression test (LDDST) response patterns and their correlation with clinicopathologic signs in dogs suspected of having Cushing's syndrome: A retrospective study

A retrospective cross-sectional study was conducted to assess the frequency of low-dose dexamethasone suppression test (LDDST) patterns in canine patients that had clinicopathologic signs consistent with Cushing's syndrome (CS). Medical records for patients of interest (N = 128) were reviewed between January 2014 and December 2020 to analyse and classify LDDST results based upon the following patterns: lack of suppression, partial suppression, complete suppression, escape, or inverse. Complete suppression, lack of suppression, partial suppression, escape, and inverse patterns were identified in 39.1%, 31.2%, 14.1%, 10.1% and 5.5% of cases respectively. LDDST results were also evaluated with respect to clinical signs, serum alkaline phosphatase (ALP) activity, urine specific gravity (USG) and adrenal ultrasonographic findings. There was no association between LDDST patterns and clinical signs (p = 0.11), increased ALP (p = 0.32), USG (p = 0.33) or adrenal ultrasonographic findings (p = 0.19). In all dogs that demonstrated complete suppression or an inverse pattern, CS was excluded by the attending clinician. The diagnosis of CS was also excluded without further exploration in 23.1%, 7.5% and 5.6% of dogs that demonstrated an escape pattern, lack of suppression and partial suppression pattern, respectively. These results suggest that the clinical significance of LDDST patterns, particularly escape and inverse patterns, are misunderstood by some clinicians, leading them to prematurely exclude the diagnosis of CS.

Cushing's syndrome caused by intra-adrenocortical adrenocorticotropic hormone in a dog

A 13‐year‐old Labrador retriever was diagnosed with Cushing's syndrome (CS) caused by primary bilateral nodular adrenocortical hyperplasia with adrenocorticotropic hormone (ACTH) expression. The pituitary origin of CS was ruled out by suppression of plasma ACTH concentration and absence of a proliferative lesion on histological evaluation of the pituitary gland using periodic acid‐Schiff (PAS) staining, reticulin staining, and immunostaining for ACTH. A pheochromocytoma also was found at necropsy examination. On histological evaluation of both adrenal glands, at the junction of the fascicular and glomerular zones, multiple cell clusters distributed in both hyperplastic adrenal cortices expressed ACTH, whereas the pheochromocytoma cells did not. These results indicate that a disease similar to primary bilateral macronodular adrenocortical hyperplasia in humans also occurs in dogs, with intra‐adrenocortical expression of ACTH, glucocorticoids excess, and clinical signs of CS. Therefore, the term ACTH‐independent could be inappropriate in some cases of bilateral adrenocortical hyperplasia and suppressed plasma ACTH concentration in dogs.

Utility of a corticotropin-releasing hormone test to differentiate pituitary-dependent hyperadrenocorticism from cortisol-producing adrenal tumors in dogs

Background

Hyperadrenocorticism (HAC) is a common endocrine disorder in dogs; however, there are no reports on the use of the corticotropin‐releasing hormone test (CRHT) to differentiate between pituitary‐dependent hyperadrenocorticism (PDH) and cortisol‐producing adrenal tumors (CPATs), both causative of HAC.

Objectives

To evaluate the usefulness of CRHT as a tool to differentiate between PDH and CPAT in dogs and to determine the reference intervals for CRHT in healthy, PDH, and CPAT dogs.

Animals

Dogs diagnosed with PDH (n = 21), CPAT (n = 6), and healthy beagle dogs (n = 33).

Methods

This prospective study included dogs with a definitive diagnosis of PDH and CPAT and healthy beagle dogs, in which CRHT was performed, were prospectively evaluated. We investigated the correlations of CRHT (endogenous adrenocorticotropic hormone [ACTH] concentration, endogenous ACTH concentration [EAC], and poststimulation ACTH concentration [PAC]) with pituitary‐to‐brain ratio (PBR) (in PDH) and with indices of adrenal ultrasonography (smaller and larger adrenal gland dorsoventral thickness in PDH and CPAT).

Results

For EAC, the area under the curve (AUC) was 0.95, with a cutoff value of 26.3 pg/mL (sensitivity: 90.62%, specificity: 87.50%). The AUC for PAC was 0.96 with a cutoff value of 54.5 pg/mL (sensitivity: 100.00%, specificity: 66.67%). The 95% reference interval for CRHT in healthy (control) dogs ranged 5.00 to 79.8 pg/mL (1.10‐17.57 pmol/L) for EAC, and 1.92 to 153.42 pg/mL (0.42‐33.78 pmol/L) for PAC. There was no significant correlation between PBR and CRHT, nor adrenal size and CRHT.

Conclusions and Clinical Importance

CRHT appears to be a rapid and reliable test for differentiating PDH from CPAT in dogs.

Prevalence and risk factors associated with systemic hypertension in dogs with spontaneous hyperadrenocorticism

Background

Systemic hypertension (SH) is common in dogs with hyperadrenocorticism (HAC) however there are not many studies assessing its prevalence and risk factors.

Objectives

To determine the prevalence and severity of SH in dogs with HAC and its association with clinical and laboratory findings to identify potential risk factors.

Animals

Sixty‐six client owned dogs with spontaneous HAC.

Methods

Retrospective cross‐sectional study. Medical records of dogs with HAC were reviewed. Systolic blood pressure (SBP) was measured using Doppler ultrasonography. Clinical signs, physical examination findings and clinicopathologic data (CBC, serum biochemistry and electrolytes, urinalysis and urinary culture, and adrenal function tests) were reviewed for analysis.

Results

Prevalence of SH (≥150 mm Hg) was 82% (54/66) and prevalence of severe SH (≥180 mm Hg) was 46% (30/66). All dogs with thrombocytosis had SH (P = .002), and a platelet count ≥438 × 10³/μL was 100% specific and 61.1% sensitive to predict SH (AUC = .802, P = .001). Median potassium levels were lower in hypertensive dogs (4.1 mEq/L, range 3.1‐5.4 mEq/L) than in normotensive ones (4.5 mEq/L, range 4.0‐5.0 mEq/L) (P = .007). Dogs with UPC ≥ 0.5 had higher median SBP than those without proteinuria (P = .03). Dogs with concurrent diabetes mellitus seemed to have a reduced risk of SH (OR = .118, 95%CI = .022‐.626, P = .02).

Conclusions and Clinical Importance

Systemic hypertension is common in dogs with HAC and is frequently severe. Blood pressure should be routinely assessed in these dogs, especially if thrombocytosis, proteinuria or low potassium concentrations are present.

Ectopic Cushing's syndrome associated with a pheochromocytoma in a dog: a case report

Background

Ectopic Cushing’s syndrome (ECS) associated with malignant tumors, such as small cell lung carcinoma, bronchial carcinoids, and pheochromocytoma, has been reported in human medicine. However, ECS related to pheochromocytoma has not been reported in dogs.

Case presentation

An 11-year-old castrated, male Scottish terrier was diagnosed with a left adrenal mass. Cushing’s syndrome was suspected based on clinical signs, including pot belly, polyuria, polydipsia, bilateral alopecia, recurrent pyoderma, and calcinosis cutis. Cushing’s syndrome was diagnosed on the basis of consistent clinical signs and repeated adrenocorticotropic hormone (ACTH) stimulation tests. In addition, tests for fractionated plasma metanephrine/normetanephrine suggested a pheochromocytoma. Unilateral adrenalectomy was performed after medical management with trilostane and phenoxybenzamine. Histopathology confirmed a diagnosis of pheochromocytoma without cortical lesions. After surgery, fractionated metanephrine/normetanephrine and the findings of low-dose dexamethasone suppression and ACTH stimulation tests were within the normal ranges without any medication. There were no clinical signs or evidence of recurrence and metastasis on thoracic and abdominal X-rays and ultrasonography up to 8 months after surgery.

Conclusions

Pheochromocytoma should be considered a differential diagnosis for dogs with Cushing’s syndrome with an adrenal tumor. A good prognosis can be expected with prompt diagnosis and surgical intervention.

Diagnosis of spontaneous hyperadrenocorticism in dogs. Part 2: Adrenal function testing and differentiating tests

Hyperadrenocorticism is a relatively common endocrine disorder in dogs that has been extensively described. However, its diagnosis remains challenging because there is no true reference standard test, and a myriad factors can affect the diagnostic performance of the commonly used adrenal function tests. Ultimately, the diagnosis is based on a combination of signalment, history and clinical findings, and a variety of diagnostic test results. The second part of this review aims to appraise available data on diagnostic performance of adrenal function tests in naturally occurring canine hyperadrenocorticism.

Diagnosis of spontaneous hyperadrenocorticism in dogs. Part 1: Pathophysiology, aetiology, clinical and clinicopathological features

Hyperadrenocorticism is a relatively common endocrine disorder in dogs. It occurs as a result of a functional pituitary or adrenal tumour, although other causes have been rarely reported. Canine hyperadrenocorticism has been extensively described but diagnosing this disease remains challenging. Few studies have investigated the clinical and clinicopathological features helpful in differentiating dogs with hyperadrenocorticism from dogs in which the disease is suspected but eventually excluded. Ultimately the diagnosis is based on a combination of multiple pieces of information emanating from the signalment, history, clinical findings, and a variety of diagnostic tests. The first part of this review aims to critically appraise the available data on epidemiology, clinical and laboratory features of naturally occurring canine hyperadrenocorticism.

Hyperadrenocorticism Caused by a Pituitary Ganglioglioma in a Dog

An 11-year-old castrated male Chihuahua dog was presented with complaints of polyuria, polydipsia, abdominal enlargement, and alopecia. Hyperadrenocorticism was diagnosed on the basis of clinical signs, blood tests, adrenocorticotropin-stimulation test results, and an elevated serum adrenocorticotropin concentration. Contrast-enhanced magnetic resonance imaging showed that the pituitary gland was enlarged, compatible with a pituitary macroadenoma. Pituitary-dependent hyperadrenocorticism was suspected, and transsphenoidal hypophysectomy was thus performed for complete resection of the tumor. After surgery, the serum adrenocorticotropin concentration normalized and the hyperadrenocorticism resolved. Histological and immunocytochemical analyses revealed a benign tumor composed of mature neuronal cells and glial cells, suggestive of a ganglioglioma with immunolabeling for adrenocorticotropin. Careful analysis of the resected tumor revealed no pituitary adenoma tissue. The clinical and histopathologic findings indicated that the ganglioglioma was directly responsible for the hyperadrenocorticism. This is the first case of hyperadrenocorticism caused by a ganglioglioma in a dog.

Cushing's syndrome-an epidemiological study based on a canine population of 21,281 dogs

The epidemiological characteristics of spontaneous hypercortisolism (HC) were derived from 21,281 client-owned dogs selected from four private veterinary clinics and one university reference center for endocrinology. The odds ratio (OR) method was employed to investigate the risk of developing HC related to breed, gender, and sexual status. The estimated prevalence of HC in the four private clinics was 0.20% [95% confidence interval (CI), 0.13–0.27] and was significantly different compared to the university reference center (1.46%; 95% CI, 1.12–1.80). Sex, breed, and age resulted in risk factors for HC. Mean (± SD) age for dogs with HC was 9.8 (± 2.5) yr. Females had higher risk for HC compared to males (OR 1.85; 95% CI, 1.24–2.75); all neutered dogs (both males and females) had higher risk than intact dogs (OR 2.54; 95% CI, 1.72–3.73); and neutered females had higher risk compared to intact females (OR 2.61; 95% CI, 1.54–4.42). Using the mixed breed dogs as a control population (OR = 1), the risk of developing HC was significantly higher in the Standard Schnauzer (OR 58.1; p < 0.0001) and Fox Terrier (OR 20.33; p < 0.0001).

With regard to HC, this study identified an overall prevalence of 0.20%. The data support the existence of sex predisposition, with the highest risk for neutered females.

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.

Adrenocortical Challenge Response and Genomic Analyses in Scottish Terriers With Increased Alkaline Phosphate Activity

Scottish terriers (ST) frequently have increased serum alkaline phosphatase (ALP) of the steroid isoform. Many of these also have high serum concentrations of adrenal sex steroids. The study's objective was to determine the cause of increased sex steroids in ST with increased ALP. Adrenal gland suppression and stimulation were compared by low dose dexamethasone (LDDS), human chorionic gonadotropin (HCG) and adrenocorticotropic hormone (ACTH) response tests. Resting plasma pituitary hormones were measured. Steroidogenesis-related mRNA expression was evaluated in six ST with increased ALP, eight dogs of other breeds with pituitary-dependent hyperadrenocorticism (HAC), and seven normal dogs. The genome-wide association of single nucleotide polymorphisms (SNP) with ALP activity was evaluated in 168 ST. ALP (reference interval 8–70 U/L) was high in all ST (1,054 U/L) and HAC (985 U/L) dogs. All HAC dogs and 2/8 ST had increased cortisol post-ACTH administration. All ST and 2/7 Normal dogs had increased sex steroids post-ACTH. ST and Normal dogs had similar post-challenge adrenal steroid profiles following LDDS and HCG. Surprisingly, mRNA of hydroxysteroid 17-beta dehydrogenase 2 (HSD17B2) was lower in ST and Normal dogs than HAC. HSD17B2 facilities metabolism of sex steroids. A SNP region was identified on chromosome 5 in proximity to HSD17B2 that correlated with increased serum ALP. ST in this study with increased ALP had a normal pituitary-adrenal axis in relationship to glucocorticoids and luteinizing hormone. We speculate the identified SNP and HSD17B2 gene may have a role in the pathogenesis of elevated sex steroids and ALP in ST.

Treating canine Cushing's syndrome: Current options and future prospects

Naturally occurring hypercortisolism, also known as Cushing's syndrome, is a common endocrine disorder in dogs that can be caused by an adenocorticotrophic hormone (ACTH)-producing pituitary adenoma (pituitary-dependent hypercortisolism, PDH; 80-85% of cases), or by an adrenocortical tumor (ACT; 15-20% of cases). To determine the optimal treatment strategy, differentiating between these two main causes is essential. Good treatment options are surgical removal of the causal tumor, i.e. hypophysectomy for PDH and adrenalectomy for an ACT, or radiotherapy in cases with PDH. Because these options are not without risks, not widely available and not suitable for every patient, pharmacotherapy is often used. In cases with PDH, the steroidogenesis inhibitor trilostane is most often used. In cases with an ACT, either trilostane or the adrenocorticolytic drug mitotane can be used. Although mostly effective, both treatments have disadvantages. This review discusses the current treatment options for canine hypercortisolism, and considers their mechanism of action, efficacy, adverse effects, and effect on survival. In addition, developments in both adrenal-targeting and pituitary-targeting drugs that have the potential to become future treatment options are discussed, as a more selective and preferably also tumor-targeted approach could have many advantages for both PDH and ACTs.

The Influence of Pituitary Size on Outcome After Transsphenoidal Hypophysectomy in a Large Cohort of Dogs with Pituitary-Dependent Hypercortisolism

Background

Transsphenoidal hypophysectomy is one of the treatment strategies in the comprehensive management of dogs with pituitary‐dependent hypercortisolism (PDH).

Objectives

To describe the influence of pituitary size at time of pituitary gland surgery on long‐term outcome.

Animals

Three‐hundred–and‐six dogs with PDH.

Methods

Survival and disease‐free fractions were analyzed and related to pituitary size; dogs with and without recurrence were compared.

Results

Four weeks after surgery, 91% of dogs were alive and remission was confirmed in 92% of these dogs. The median survival time was 781 days, median disease‐free interval was 951 days. Over time, 27% of dogs developed recurrence of hypercortisolism after a median period of 555 days. Dogs with recurrence had significantly higher pituitary height/brain area (P/B) ratio and pre‐operative basal urinary corticoid‐to‐creatinine ratio (UCCR) than dogs without recurrence. Survival time and disease‐free interval of dogs with enlarged pituitary glands was significantly shorter than that of dogs with a non‐enlarged pituitary gland. Pituitary size at the time of surgery significantly increased over the 20‐year period. Although larger tumors have a less favorable prognosis, outcome in larger tumors improved over time.

Conclusions and Clinical Importance

Transsphenoidal hypophysectomy is an effective treatment for PDH in dogs, with an acceptable long‐term outcome. Survival time and disease‐free fractions are correlated negatively with pituitary gland size, making the P/B ratio an important pre‐operative prognosticator. However, with increasing experience, and for large tumors, pituitary gland surgery remains an option to control the pituitary mass and hypercortisolism.

Effect of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs

OBJECTIVE

To determine the effects of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs.

ANIMALS

10 healthy neutered dogs.

PROCEDURES

Each dog received dexamethasone (0.01 mg/kg), synthetic ACTH (5 μg/kg), or saline (0.9% NaCl) solution (0.5 mL) IV at intervals of ≥ 30 days. Plasma endogenous ACTH concentrations were measured before (baseline; time 0) and 1, 8, 12, and 24 hours after drug administration; serum cortisol concentrations were measured before and 1 hour after synthetic ACTH and saline solution administration and 8 hours after dexamethasone administration.

RESULTS

Analysis of serum cortisol concentrations confirmed effects of drug administration. Dexamethasone significantly decreased the endogenous ACTH concentration from the baseline value at both 8 and 12 hours. Synthetic ACTH administration significantly decreased the endogenous ACTH concentration from the baseline value at 8 hours. Saline solution administration had no significant effect on endogenous ACTH concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Dexamethasone and synthetic ACTH administered IV at doses used routinely during testing for hyperadrenocorticism caused significant but transient reductions of endogenous ACTH concentrations in healthy dogs. Thus, a 2-hour washout period following ACTH stimulation testing before collection of samples for measurement of the endogenous ACTH concentration may be insufficient. Although this effect has not been verified in dogs with hyperadrenocorticism, these data suggested that samples for measurement of endogenous ACTH concentrations should be obtained before or > 8 hours after initiation of an ACTH stimulation test or before or > 12 hours after the start of a low-dose dexamethasone suppression test.

Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal)

This report offers a consensus opinion on the diagnosis of spontaneous canine hyperadrenocorticism. The possibility that a patient has hyperadrenocorticism is based on the history and physical examination. Endocrine tests should be performed only when clinical signs consistent with HAC are present. None of the biochemical screening or differentiating tests for hyperadrenocorticism are perfect. Imaging can also play a role. Awareness of hyperadrenocorticism has heightened over time. Thus, case presentation is more subtle. Due to the changes in manifestations as well as test technology the Panel believes that references ranges should be reestablished. The role of cortisol precursors and sex hormones in causing a syndrome of occult hyperadrenocorticism remains unclear.

Recent advances in the diagnosis of Cushing's syndrome in dogs

Hypercortisolism is a common condition in dogs and can be defined as the physical and biochemical changes that result from prolonged exposure to inappropriately high plasma concentrations of (free) cortisol, whatever its' cause. This disorder is often called Cushing's syndrome, after Harvey Cushing, the neurosurgeon who first described the human syndrome in 1932.

Interpretation of laboratory tests for canine Cushing's syndrome

Hypercortisolism (HC) is a common disease in dogs. This article will review the laboratory tests that are available for diagnosis of HC and laboratory tests for differentiating between causes of HC. An emphasis will be made on the clinical process that leads to the decision to perform those tests and common misconceptions and issues that arise when performing them. To choose between the adrenocorticotropic hormone (ACTH)-stimulation test and the low-dose dexamethasone suppression test (LDDST), the advantages and disadvantages of both tests should be considered, as well as the clinical presentation. If the index of suspicion of HC is high and other diseases have been appropriately ruled out, the specificity of the ACTH stimulation test is reasonably high with an expected high positive predictive value. Because of the low sensitivity, a negative result in the ACTH stimulation test should not be used to rule out the diagnosis of HC. The LDDST is more sensitive but also less specific and affected more by stress. A positive result on the urine cortisol:creatinine ratio does not help to differentiate HC from other diseases. A negative result on the urine cortisol:creatinine ratio indicates that the diagnosis of HC is very unlikely. The LDDST is useful in differentiating pituitary-dependent HC from an adrenal tumor in about two thirds of all dogs with HC. Differentiation of HC from diabetes mellitus, liver diseases, and hypothyroidism cannot be based solely on endocrine tests. Clinical signs, imaging studies, histopathology, and response to treatment should all be considered.

Use of computed tomography adrenal gland measurement for differentiating ACTH dependence from ACTH independence in 64 dogs with hyperadenocorticism

BACKGROUND

The measurement of adrenal gland size on computed tomography (CT) scan has been proposed for the etiological diagnosis of hyperadrenocorticism (HAC) in dogs. Symmetric adrenal glands are considered to provide evidence for ACTH-dependent hyperadrenocorticism (ADHAC), whereas asymmetry suggests ACTH-independent hyperadrenocorticism (AIHAC). However, there are currently no validated criteria for such differentiation.

OBJECTIVE

The aim of this retrospective study was to compare various adrenal CT scan measurements and the derived ratios in ADHAC and AIHAC cases, and to validate criteria for distinguishing between these conditions in a large cohort of dogs.

ANIMALS

Sixty-four dogs with HAC (46 ADHAC, 18 AIHAC).

METHODS

Dogs with confirmed HAC and unequivocal characterization of its origin were included. Linear measurements of adrenal glands were made on both cross-sectional and reformatted images.

RESULTS

An overlap was systematically observed between the AIHAC and ADHAC groups for all measurements tested. Overlaps also were observed for ratios tested. For the maximum adrenal diameter ratio derived from reformatted images (rADR), only 1/18 AIHAC dogs had a rADR within the range for ADHAC. For a threshold of 2.08, the 95% confidence intervals for estimated sensitivity and specificity extended from 0.815 to 1.000 and from 0.885 to 0.999, respectively, for AIHAC diagnosis.

CONCLUSION AND CLINICAL IMPORTANCE

Measurements from cross-sectional or reformatted CT scans are of little use for determining the origin of HAC. However, rADR appears to distinguish accurately between ADHAC and AIHAC, with a rADR > 2.08 highly suggestive of AIHAC.

Tailored reference limits for urine corticoid:creatinine ratio in dogs to answer distinct clinical questions

To establish reference intervals for the urinary corticoid:creatinine ratio (UCCR) determined by chemiluminometric immunoassay, UCCR was measured by this method in 50 healthy dogs. To assess the diagnostic performance of different cut-off levels, the UCCR of 66 dogs with hyperadrenocorticism and 87 dogs with diseases mimicking hyperadrenocorticism were used to construct a receiver operating characteristic (ROC) curve. The upper reference limit derived from morning samples in healthy dogs was 30.81 × 10(-6). The area under the ROC curve was 0.94. The diagnostic cut-off with the highest negative likelihood ratio was 26.5 × 10(-6) (sensitivity 1, specificity 0.54), whereas the cut-off with the highest positive likelihood ratio was 161.2 × 10(-6) (specificity 0.988, sensitivity 0.515). The application of these two different diagnostic cut-offs eliminated the necessity to perform additional tests in 53 per cent of the patient population.

Cushing's syndrome, glucocorticoids and the kidney

Glucocorticoids (GCs) affect renal development and function in fetal and mature kidneys both indirectly, by influencing the cardiovascular system, and directly, by their effects on glomerular and tubular function. Excess GCs due to endogenous GC overproduction in Cushing's syndrome or exogenous GC administration plays a pivotal role in hypertension and causes increased cardiac output, total peripheral resistance and renal blood flow. Glucocorticoids increase renal vascular resistance (RVR) in some species and experimental settings and decrease RVR in others. Short term administration of adrenocorticotrophic hormone or GCs causes an increased glomerular filtration rate (GFR) in humans, rats, sheep and dogs. Interestingly, chronic exposure may cause a decreased GFR in combination with a higher cardiovascular risk in human patients with Cushing's syndrome. Glomerular dysfunction leads to proteinuria and albuminuria in canine and human Cushing's patients, and some cases also show histological evidence of glomerulosclerosis. Tubular dysfunction is reflected by an impaired urinary concentrating ability and disturbed electrolyte handling, which can potentially result in increased sodium reabsorption, hypercalciuria and urolithiasis. Conversely, chronic kidney disease can also alter GC metabolism. More research needs to be performed to further evaluate the renal consequences of Cushing's syndrome because of its implications for therapeutic aspects as well as the general well-being of the patient. Because there is a high incidence of Cushing's syndrome in canines, which is similar to the syndrome in humans, dogs are an interesting animal model to investigate the link between hypercortisolism and renal function.

Adrenal Pheochromocytoma With Contralateral Adrenocortical Adenoma in a Cat

A 7-year-old, neutered male cat was presented with a 6-month history of progressive polyuria, polydipsia, polyphagia, aggression, and weight gain. Previous blood work, urinalysis, and radiographs did not delineate a cause for the clinical signs. An ultrasound revealed bilateral adrenal gland enlargement. A low-dose dexamethasone suppression test was consistent with hyperadrenocorticism. Based on these findings, bilateral adrenalectomy was attempted and successfully performed. Histopathology was consistent with a cortical adenoma in the right adrenal gland and a pheochromocytoma in the left adrenal gland. This association has never been reported in the cat.

Effects of trilostane on the pituitary-adrenocortical and renin-aldosterone axis in dogs with pituitary-dependent hypercortisolism

The medical records of 63 dogs with pituitary-dependent hypercortisolism (PDH) before and during treatment with trilostane were reviewed retrospectively. The correct trilostane dosage in dogs with PDH was based on the resolution of clinical signs and the results of an adrenocorticotropic hormone (ACTH) stimulation test. The mean (+/-SD) dose rate of trilostane to achieve good clinical control was 2.8+/-1.0mg/kg bodyweight. Trilostane treatment resulted in a significant decline in basal plasma cortisol concentrations. The median plasma ACTH concentration (39 pmol/L, range 7-132 pmol/L; n=60) at the optimal trilostane dosage time was significantly higher (P<0.001) than before treatment (13 pmol/L, range 2-102 pmol/L). These values did not overlap with plasma ACTH concentrations (range 212-307 pmol/L) of five PDH dogs with trilostane-induced hypocortisolism. The median cortisol/ACTH ratio in well-controlled dogs (0.23, range 0.03-2.5; n=46) was significantly lower (P<0.001) than before treatment (2.59, range 0.27-13.25). Trilostane treatment resulted in an insignificant decrease in plasma aldosterone concentration (PAC), but the median plasma renin activity (PRA) at the time the trilostane dosage was considered optimal (265 fmol/L/s, range 70-3280 fmol/L/s; n=18) was significantly higher (P<0.001) than prior to treatment (115 fmol/L/s, range 15-1330 fmol/L/s). Similarly, the median PAC/PRA ratio during trilostane treatment (0.16, range 0.003-0.92; n=17) was significantly lower (P<0.001) than before treatment (median 0.44, range 0.04-1.33). Trilostane affected both the hypothalamic-pituitary-adrenocortical and the renin-aldosterone axes. The results also suggested that basal plasma ACTH concentration may be used to detect trilostane overdosage.

Hypokalaemic paresis, hypertension, alkalosis and adrenal-dependent hyperadrenocorticism in a dog

Generalised paresis, severe hypokalaemia and kaliuresis, metabolic alkalosis and hypertension, characteristic of mineralocorticoid excess, were identified in a dog with hyperadrenocorticism due to a functional adrenocortical carcinoma. Aldosterone concentration was decreased and deoxycorticosterone concentration increased in the presence of hypokalaemia. These metabolic abnormalities resolved with resection of the carcinoma. Mineralocorticoid excess in dogs with hyperadrenocorticism is generally considered to be of little clinical significance but resulted in the acute presentation of this patient. The possible pathogenesis of mineralocorticoid excess in this case of canine hyperadrenocorticism is discussed.

Empty sella syndrome, hyperadrenocorticism and megaoesophagus in a dachshund

A five-year-old, entire, male dachshund was presented with a five day history of hypersalivation and regurgitation as well as polyuria and polydipsia for several months. Chest radiographs demonstrated megaoesophagus and aspiration pneumonia. Furthermore, hyperadrenocorticism was demonstrated by means of elevations in levels of serum alkaline phosphatase and cholesterol, decreased urinary specific gravity, increased response to adrenocorticotropic hormone stimulation, insufficient suppression of the post-dexamethasone plasma cortisol levels, an increased endogenous adrenocorticotropic hormone concentration and bilaterally enlarged adrenal glands on abdominal ultrasound. The dog became severely dyspnoeic and was euthanased after magnetic resonance imaging was performed. The magnetic resonance imaging and necropsy revealed the sellar region mainly filled with fluid, with only small tissue remnants, a condition defined as empty sella syndrome in human medicine. To the author's knowledge, this is the first dog described with empty sella syndrome and only the second dog described with hyperadrenocorticism secondary to ectopic adrenocorticotropic hormone production. However, the association between empty sella syndrome and hyperadrenocorticism may be no more than incidental.

Diagnosis of Hyperadrenocorticism in Dogs

A presumptive diagnosis of hyperadrenocorticism in dogs can be made from clinical signs, physical examination, routine laboratory tests, and diagnostic imaging findings, but the diagnosis must be confirmed by use of pituitary-adrenal function tests. Screening tests designed to diagnose hyperadrenocorticism include the corticotropin (adrenocorticotropic hormone; ACTH) stimulation test, low-dose dexamethasone suppression test, and the urinary cortisol:creatinine ratio. None of these screening tests are perfect, and all are capable of giving false-negative and false-positive test results. Because of the limitation of these diagnostic tests, screening for hyperadrenocorticism must be reserved for dogs in which the disease is strongly suspected on the basis of historical and clinical findings. Once a diagnosis has been confirmed, the next step in the workup is to use one or more tests and procedures to distinguish pituitary-dependent from adrenal-dependent hyperadrenocorticism. Endocrine tests in this category include the high-dose dexamethasone suppression test and endogenous plasma ACTH measurements. Imaging techniques such as abdominal radiography, ultrasonography, computed tomography, and magnetic resonance imaging can also be extremely helpful in determining the cause.

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, alpha-MSH, and TSH were collected at -15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation. MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for FSH after suprapituitary stimulation were significantly higher before treatment than at 5, 8, and 11 months of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and alpha-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH. In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic-pituitary-adrenocortical axis, and unaffected secretion of prolactin and alpha-MSH.