Prognostic factors for outcome after transsphenoidal hypophysectomy in dogs with pituitary-dependent hyperadrenocorticism

Effect of pituitary-dependent hypercortisolism on the survival of dogs treated with radiotherapy for pituitary macroadenomas

BACKGROUND

Radiotherapy (RT) is an effective treatment for dogs presented with neurologic signs caused by pituitary tumors. However, its impact on the outcome of concurrent pituitary-dependent hypercortisolism (PDH) is controversial.

OBJECTIVES

Determine whether dogs with PDH have longer survival after pituitary RT compared with dogs with nonhormonally active pituitary masses and to evaluate whether clinical, imaging, and RT variables affect survival.

ANIMALS

Ninety-four dogs divided into 2 groups: PDH and non-PDH, based on the presence of hypercortisolism. Forty-seven dogs were allocated to the PDH group and 47 to the non-PDH group.

METHODS

Retrospective cohort study in which clinical records of dogs undergoing RT for pituitary macroadenomas between 2008 and 2018 at 5 referral centers were retrospectively evaluated.

RESULTS

Survival was not statistically different between PDH and non-PDH groups (median survival time [MST], 590 days; 95% confidence interval [CI], 0-830 days and 738 days; 95% CI, 373-1103 days, respectively; P = .4). A definitive RT protocol was statistically associated with longer survival compared with a palliative protocol (MST 605 vs 262 days, P = .05). The only factor statistically associated with survival from multivariate Cox proportional hazard analysis was total radiation dose (Gy) delivered (P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

No statistical difference in survival was identified between the PDH and non-PDH groups, and longer survival was associated with higher Gy delivered.

Challenges of transsphenoidal pituitary surgery in severe brachycephalic dogs

Introduction

Transsphenoidal hypophysectomy is the standard surgical technique for the excision of pituitary neoplasms. Anatomy may be more obscured in brachycephalic skull types due to the crowding of soft tissue and osseous structures. We describe the unique challenges to approach the sphenoid bone and localize the correct burr hole site in severe brachycephalic dogs.

Materials and methods

A single institution retrospective case series of brachycephalic dogs with pituitary-dependent hypercortisolism (PDH). Preoperative computed tomography enabled 3D-, and cross-sectional reconstruction to plan and dry-practice the position of the ideal burr hole in relation to the sella turcica, pterygoid hamular processes, and hard palate. Rostral burring of the caudal hard palate obscuring the direct sphenoid approach necessitated adaptations to the original transsphenoidal hypophysectomy procedure. Postoperative outcomes and complications with respect to those seen in mesocephalic dogs are described.

Results

Ten brachycephalic dogs including French Bulldogs (n = 9) and a single Dogue de Bordeaux were included. All dogs were diagnosed with PDH and had preoperative advanced imaging performed on the skull. All but one dog had an enlarged pituitary gland, with a median pituitary/brain value of 0.5 (range 0.21-0.9). A total of 11 transsphenoidal hypophysectomy procedures were performed in these 10 dogs. Rostral extension of the soft palate incision into the hard palate was performed to access the burr hole site on the sphenoid bone. Major complications included aspiration pneumonia (n = 1), severe gastroesophageal reflux (n = 1), and central nervous signs (=1). All dogs survived until discharge, with a median time to follow-up of 618 days (range 79-1,669 days). Seven dogs experienced long-term remission of PDH.

Conclusion

Brachycephalic dogs undergoing transsphenoid al hypophysectomy benefit from meticulous presurgical planning and extension of the approach into the caudal hard palate. Advanced surgical skills can render a good outcome in a technically challenging environment.

Presumed pituitary apoplexy in 26 dogs: Clinical findings, treatments, and outcomes

BACKGROUND

Pituitary apoplexy refers to hemorrhage or infarction within the pituitary gland resulting in acute neurological abnormalities. This condition is poorly described in dogs.

OBJECTIVES

To document presenting complaints, examination findings, endocrinopathies, magnetic resonance imaging (MRI), treatments, and outcomes of dogs with pituitary apoplexy.

ANIMALS

Twenty-six client-owned dogs with acute onset of neurological dysfunction.

METHODS

Retrospective case series. Dogs were diagnosed with pituitary apoplexy if MRI or histopathology documented an intrasellar or suprasellar mass with evidence of hemorrhage or infarction in conjunction with acute neurological dysfunction. Clinical information was obtained from medical records and imaging reports.

RESULTS

Common presenting complaints included altered mentation (16/26, 62%) and gastrointestinal dysfunction (14/26, 54%). Gait or posture changes (22/26, 85%), mentation changes (18/26, 69%), cranial neuropathies (17/26, 65%), cervical or head hyperpathia (12/26, 46%), and hyperthermia (8/26, 31%) were the most frequent exam findings. Ten dogs (38%) lacked evidence of an endocrinopathy before presentation. Common MRI findings included T1-weighted hypo- to isointensity of the hemorrhagic lesion (21/25, 84%), peripheral enhancement of the pituitary mass lesion (15/25, 60%), brain herniation (14/25, 56%), and obstructive hydrocephalus (13/25, 52%). Fifteen dogs (58%) survived to hospital discharge. Seven of these dogs received medical management alone (median survival 143 days; range, 7-641 days) and 8 received medications and radiation therapy (median survival 973 days; range, 41-1719 days).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with pituitary apoplexy present with a variety of acute signs of neurological disease and inconsistent endocrine dysfunction. Dogs that survive to discharge can have a favorable outcome.

Clinical characteristics and outcome in 15 dogs treated with transsphenoidal hypophysectomy for nonfunctional sellar masses

OBJECTIVE

To characterize the clinical features, neurological examination findings, diagnostic imaging results, histopathological findings, and outcome following transsphenoidal hypophysectomy (TSH) in dogs with nonfunctional sellar masses (NFSM).

STUDY DESIGN

Multi-institutional retrospective study.

METHODS

Medical records of dogs that underwent TSH for a NFSM were reviewed for clinical signs, physical and neurological examination findings, diagnostic imaging results, endocrine testing, surgery reports, and outcome. Magnetic resonance (MR) imaging was rereviewed, and tumors were classified using the previously described system according to pituitary tumor extension and vascular involvement. Owners of dogs that survived to discharge were contacted.

RESULTS

The majority of dogs presented for mentation change (12/15). The mean pituitary to brain ratio (P/B ratio) was 1.05 (0.6-1.4). Eight dogs had a tumor imaging classification of 5B. Eleven dogs were diagnosed with a nonfunctional pituitary adenoma (NFPA). Perioperative mortality was 33% (5/15). The median survival for all dogs was 232 days (0-1658). When dogs that did not survive to discharge were excluded, the median survival time was 708 days. Seven of 10 dogs that survived the perioperative period received adjunctive therapy. Owner assessment of outcome was excellent (6/7) to good (1/7).

CONCLUSION

The common presenting complaint for dogs with large NFSM causing mass effect was mentation changes. Dogs with NFPA that survived to discharge and received adjunctive therapy had good to excellent outcomes.

CLINICAL SIGNIFICANCE

Transsphenoidal debulking with adjunctive therapy can be considered for the treatment of NFSM causing clinical signs of mass effect in dogs. Successful long-term outcomes are possible.

Ultrasonographic patterns, clinical findings, and prognostic variables in dogs from Asia with gallbladder mucocele

BACKGROUND

Gallbladder mucocele (GBM) is a common biliary disorder in dogs that can be categorized into 6 types, but the value of this classification scheme remains unknown. Cholecystectomy is associated with high death rates and warrants additional interrogation.

OBJECTIVES

Investigate the clinical value of ultrasonographic diagnosis of type of GBM and identify prognostic factors in dogs with GBM undergoing cholecystectomy.

ANIMALS

Two hundred sixteen dogs.

METHODS

Retrospective cohort study. Dogs with GBM diagnosed from 2014 to 2019 at 6 veterinary referral hospitals in Asia. Ultrasonogram images were reviewed and a GBM type (ie, types I-VI) assigned.

RESULTS

Dogs with GBM type V as compared to I (OR, 8.6; 95% CI, 2.6-27.8; P < .001) and III (OR, 10.0; 95% CI, 2.5-40.8; P = .001), and dogs with type VI compared to I (OR, 10.5; 95% CI, 1.8-61.2; P = .009) and III (OR, 12.3; 95% CI, 1.8-83.9; P = .01) were more likely to exhibit signs of biliary tract disease. Independent predictors of death after cholecystectomy included age (OR, 2.81; 95% CI, 1.41-5.59; P = .003) and intraoperative systolic blood pressure (SBP) nadir. There was an interaction between SBP nadir and gallbladder rupture; SBP nadir in dogs with (OR, 0.92; 95% CI, 0.89-0.94; P < .001) and without (OR, 0.88; 95% CI, 0.82-0.93; P < .001) gallbladder rupture.

CONCLUSION AND CLINICAL IMPORTANCE

Increasing developmental stage of GBM could be associated with an increased likelihood of biliary tract related clinical signs. Nadir SBP deserves further investigation as a prognostic or potentially modifiable variable, particularly in the presence of gallbladder rupture.

Circulating MicroRNAs as Non-invasive Biomarkers for Canine Cushing's Syndrome

Canine Cushing's syndrome (hypercortisolism) can be caused by a pituitary tumor (pituitary-dependent hypercortisolism; PDH) or a cortisol-secreting adrenocortical tumor (csACT). For both cases, non-invasive biomarkers that could pre-operatively predict the risk of recurrence after surgery would greatly impact clinical decision making. The aim of this study was to determine whether circulating microRNAs (miRNAs) can be used as diagnostic (presence of PDH or csACT) and/or prognostic (disease recurrence, histological grade) non-invasive biomarkers for canine Cushing's syndrome. After a pilot study with 40 miRNAs in blood samples of healthy dogs (n = 3), dogs with PDH (n = 3) and dogs with a csACT (n = 4), we selected a total of 20 miRNAs for the definitive study. In the definitive study, these 20 miRNAs were analyzed in blood samples of healthy dogs (n = 6), dogs with PDH (n = 19, pre- and post-operative samples) and dogs with a csACT (n = 26, pre-operative samples). In dogs with PDH, six miRNAs (miR-122-5p, miR-126-5p, miR-141-3p, miR-222-3p, miR-375-3p and miR-483-3p) were differentially expressed compared to healthy dogs. Of one miRNA, miR-122-5p, the expression levels did not overlap between healthy dogs and dogs with PDH (p = 2.9x10-4), significantly decreased after hypophysectomy (p = 0.013), and were significantly higher (p = 0.017) in dogs with recurrence (n = 3) than in dogs without recurrence for at least one year after hypophysectomy (n = 7). In dogs with csACTs, two miRNAs (miR-483-3p and miR-223-3p) were differentially expressed compared to healthy dogs. Additionally, miR-141-3p was expressed significantly lower (p = 0.009) in dogs with csACTs that had a histopathological Utrecht score of ≥ 11 compared to those with a score of <11. These results indicate that circulating miRNAs have the potential to be non-invasive biomarkers in dogs with Cushing's syndrome that may contribute to clinical decision making.

Case Report: Radioactive Holmium-166 Microspheres for the Intratumoral Treatment of a Canine Pituitary Tumor

Introduction: In this case study, a client-owned dog with a large pituitary tumor was experimentally treated by intratumoral injection of radioactive holmium-166 microspheres (166HoMS), named 166Ho microbrachytherapy. To our knowledge, this is the first intracranial intratumoral treatment through needle injection of radioactive microspheres. Materials and Methods: A 10-year-old Jack Russell Terrier was referred to the Clinic for Companion Animal Health (Faculty of Veterinary Medicine, Utrecht University, The Netherlands) with behavioral changes, restlessness, stiff gait, and compulsive circling. MRI and CT showed a pituitary tumor with basisphenoid bone invasion and marked mass effect. The tumor measured 8.8 cm3 with a pituitary height-to-brain area (P/B) ratio of 1.86 cm-1 [pituitary height (cm) ×10/brain area (cm2)]. To reduce tumor volume and neurological signs, 166HoMS were administered in the tumor center by transsphenoidal CT-guided needle injections. Results: Two manual CT-guided injections were performed containing 0.6 ml of 166HoMS suspension in total. A total of 1097 MBq was delivered, resulting in a calculated average tumor dose of 1866 Gy. At 138 days after treatment, the tumor volume measured 5.3 cm3 with a P/B ratio of 1.41 cm-1, revealing a total tumor volume reduction of 40%. Debulking surgery was performed five months after 166HoMS treatment due to recurrent neurological signs. The patient was euthanized two weeks later at request of the owners. Histopathological analysis indicated a pituitary adenoma at time of treatment, with more malignant characteristics during debulking surgery. Conclusion: The 40% tumor volume reduction without evident severe periprocedural side effects demonstrated the feasibility of intracranial intratumoral 166HoMS treatment in this single dog.

Pituitary Surgery: Changing the Paradigm in Veterinary Medicine in the United States

Medical management is currently the most common treatment for pituitary-dependent hyperadrenocorticism and hypersomatotropism/acromegaly in veterinary medicine. Medical management does not provide a cure for either disease process, and rarely is pituitary imaging a part of initial diagnostics. Early pituitary imaging in animals with clinically functional pituitary tumors provides a baseline assessment, allows monitoring of tumor changes, and permits radiation and surgical planning. Surgery is the only treatment for pituitary tumors that has curative intent and allows for a definitive diagnosis. Surgical removal of pituitary tumors via transsphenoidal hypophysectomy is an effective treatment for clinical pituitary tumors in patients exhibiting endocrine abnormalities associated with pituitary-dependent hyperadrenocorticism and hypersomatotropism. Surgery, however, is rarely pursued until patients have failed medical management, and often not until they are showing neurologic signs, making surgical success challenging. It is well documented that dogs surgically treated when the pituitary mass is small have a lower mortality, a lower recurrence rate, and a longer survival than those with larger pituitary masses. Providing owners with the option of early pituitary imaging in addition to medical, surgical, and radiation treatment options should be the standard of care for animals diagnosed with pituitary-dependent hyperadrenocorticism or hypersomatotropism.

Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection

Pituitary-dependent hyperadrenocorticism (PDH) is the cause of approximately 80-85% of naturally occurring cases of hyperadrenocorticism(HAC) in canines and is triggered by an adrenocorticotropic hormone (ACTH)-producing pituitary adenoma or hyperplasia of the corticotroph in the pituitary anterior lobe or intermediate lobe. Transsphenoidal surgery(TSS) is an effective treatment that can directly remove pituitary tumors that cause PDH in canines under a single course of general anesthesia. However, careful evaluations of the definitive diagnosis, adenoma size and growth rate, relationship with surrounding tissue, general condition, and neurosurgical procedural skill involved in each case are important to determine TSS suitability. The basic principle is to confirm that the present HAC case is PDH, that is, an ACTH-producing adenoma or the hyperplasia of the corticotroph originating from either the pituitary anterior or intermediate lobe. Evaluations based on endocrinology, particularly plasma ACTH concentration, and imaging diagnosis, particularly MRI is essential for definitive diagnosis. Enlarged pituitary tumors can shorten the post-TSS survival time, increase the recurrence rate of clinical symptoms, and increase the risk for developing permanent central diabetes insipidus. Therefore, complete removal of adenomas of up to Grade IIIA according to the MRI-based classification system is relatively easy to achieve with TSS, and long-term remission and survival can be expected.

Dynamics of postoperative serum cortisol after transsphenoidal surgery for Cushing's disease: implications for immediate reoperation and remission

OBJECTIVESuccessful transsphenoidal surgery for adrenocorticotropin hormone (ACTH)-producing pituitary tumors is associated with subnormal postoperative serum cortisol levels, which may guide decisions regarding immediate reoperation. However, little is known about the detailed temporal course of changes in serum cortisol in the immediate postoperative period, and the relationship of postoperative cortisol dynamics to remission and late recurrence.METHODSA single-center retrospective cohort analysis was performed for all patients undergoing pituitary surgery from 2007 through 2015. Standardized diagnostic and treatment algorithms were applied to all patients with potential Cushing's disease (CD), including microsurgical transsphenoidal adenomectomy (TSA) by a single surgeon. All patients had serum cortisol levels drawn at 6-hour intervals for 72 hours after surgery, and were offered reoperation within 3 days for normal or supranormal postoperative cortisol levels. Primary outcomes were 6-month remission and late recurrence; secondary outcomes were persistent postoperative hypocortisolism and surgical morbidity. Discriminatory levels of postoperative serum cortisol for predicting remission were calculated at various intervals after surgery using receiver operating characteristic (ROC) curves.RESULTSAmong 89 patients diagnosed with CD, 81 underwent initial TSA for a potentially curable lesion; 23 patients (25.8%) underwent an immediate second TSA. For the entire cohort, 6-month remission was achieved in 77.8% and late recurrences occurred in 9.5%, at a mean of 43.5 months. Compared with patients with a single surgery, those with an immediate second TSA had similar rates of remission (78.3% vs 77.6%) and late recurrence (5.6% vs 11.1%). The rate of hypocortisolism for patients with 2 surgeries (12/23, 52.2%) was significantly greater than that for patients with single surgeries (13/58, 22.4%; p < 0.001). There was no difference in the incidence of CSF leaks between the first and second operations. Remission was achieved in 58 (92.1%) of 64 patients who completed the 2-surgery protocol. The temporal course of postoperative serum cortisol levels among patients varied considerably, with subnormal nadir levels < 2 μg/dl occurring between 12 hours and 66 hours. Patients achieving remission had significantly lower mean serum cortisol levels at every time point after surgery (p < 0.01). By ROC curve analysis, nadir cortisol levels < 2.1 μg/dl were predictive of 6-month remission for the entire cohort over 3 days (positive predictive value [PPV] = 94%); discriminating cortisol levels for predicting remission on postoperative day (POD) 2 were < 5.4 μg/dl (PPV = 97%), although patients with remission after postoperative cortisol levels of 2-5 μg/dl had a significantly higher rate of late recurrence.CONCLUSIONSThere is substantial variation in the temporal course of serum cortisol levels over the first 72 hours after TSA for CD, with nadir levels predictive for remission occurring as late as POD 3. Although a cortisol level of 2.1 μg/dl at any point was an accurate predictor of 6-month remission, levels less than 5.4 μg/dl on POD 2 were reasonably accurate. These data may enable decisions regarding the efficacy of an immediate second surgical procedure performed during the same hospitalization; immediate reoperation is associated with excellent remission rates and low recurrence rates in patients otherwise unlikely to achieve remission, but carries a higher risk of permanent hypocortisolism.

Survival analysis of 219 dogs with hyperadrenocorticism attending primary care practice in England

BACKGROUND

Hyperadrenocorticism is an endocrine disease routinely encountered within primary care practice; however, few studies evaluating survival beyond diagnosis have studied this population.

METHODS

This retrospective cohort study analysed the electronic patient records of 219 cases of hyperadrenocorticism from a sample of dogs attending primary care practices in England. Kaplan-Meier plots examined the cumulative survival and Cox proportional hazard regression modelling identified factors associated with the hazard of all-cause mortality.

RESULTS

In the analysis, 179/219 (81.7 per cent) hyperadrenocorticism cases died during the study period with a median survival time from first diagnosis of 510 days (95% CI 412 to 618 days). Trilostane was used in 94.1 per cent of cases and differentiation between pituitary-dependent and adrenal-dependent disease was made in 20.1 per cent of cases. In the multivariable analysis, dogs weighing greater than or equal to 15 kg (HR 1.51, 95% CI 1.06 to 2.15, P=0.023) and those diagnosed greater than or equal to 13 years of age (HR 3.74, 95% CI 2.29 to 6.09, P<0.001) had increased hazards of all-cause mortality. Dogs that had their initial trilostane dose increased had a favourable prognosis (HR 0.49, 95% CI 0.32 to 0.76, P=0.015).

CONCLUSION

This study shows that survival from diagnosis of hyperadrenocorticism appears fair for many dogs and provides primary care practitioners with relatable benchmark prognostic figures.

Effect of clinical signs, endocrinopathies, timing of surgery, hyperlipidemia, and hyperbilirubinemia on outcome in dogs with gallbladder mucocele

Gallbladder mucocele (GBM) is a common extra-hepatic biliary syndrome in dogs with death rates ranging from 7 to 45%. Therefore, the aim of this study was to identify the association of survival with variables that could be utilized to improve clinical decisions. A total of 1194 dogs with a gross and histopathological diagnosis of GBM were included from 41 veterinary referral hospitals in this retrospective study. Dogs with GBM that demonstrated abnormal clinical signs had significantly greater odds of death than subclinical dogs in a univariable analysis (OR, 4.2; 95% CI, 2.14-8.23; P<0.001). The multivariable model indicated that categorical variables including owner recognition of jaundice (OR, 2.12; 95% CI, 1.19-3.77; P=0.011), concurrent hyperadrenocorticism (OR 1.94; 95% CI, 1.08-3.47; P=0.026), and Pomeranian breed (OR, 2.46; 95% CI 1.10-5.50; P=0.029) were associated with increased odds of death, and vomiting was associated with decreased odds of death (OR, 0.48; 95% CI, 0.30-0.72; P=0.001). Continuous variables in the multivariable model, total serum/plasma bilirubin concentration (OR, 1.03; 95% CI, 1.01-1.04; P<0.001) and age (OR, 1.17; 95% CI, 1.08-1.26; P<0.001), were associated with increased odds of death. The clinical utility of total serum/plasma bilirubin concentration as a biomarker to predict death was poor with a sensitivity of 0.61 (95% CI, 0.54-0.69) and a specificity of 0.63 (95% CI, 0.59-0.66). This study identified several prognostic variables in dogs with GBM including total serum/plasma bilirubin concentration, age, clinical signs, concurrent hyperadrenocorticism, and the Pomeranian breed. The presence of hypothyroidism or diabetes mellitus did not impact outcome in this study.

Sequential Treatment of a Large Pituitary Corticotroph Neoplasm and Associated Neurological Signs in a Dog

No standardized treatment guidelines are reported in veterinary medicine for dogs with large pituitary corticotroph neoplasms causing neurological signs, and such dogs usually have a short overall survival. When these dogs undergo pituitary surgery and the tumor regrows there are few reports of subsequent treatments. A 7 yr old male Maltese diagnosed with pituitary-dependent hypercortisolism developed seizures in conjunction with a large pituitary corticotroph adenoma and underwent transsphenoidal hypophysectomy. After 3 yr of clinical remission, hypercortisolism recurred, and trilostane therapy was initiated. One year later, the dog developed new neurological signs and computed tomography revealed regrowth of a large pituitary mass that was then treated with radiation therapy. The dog lived disease-free for 3 more yr. At postmortem examination, a more aggressive pituitary neoplasm than the one examined at the time of surgery was found, which is suggestive of malignant transformation into a carcinoma despite the absence of convincing metastasis.

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.

Concurrent pituitary and adrenocortical lesions on computed tomography imaging in dogs with spontaneous hypercortisolism

Background

Spontaneous hypercortisolism or Cushing's syndrome in dogs is either pituitary or adrenal dependent, but concurrent pituitary and adrenal hypercortisolism also has been reported.

Objective

To determine how often concurrent pituitary and adrenal lesions are present in dogs with spontaneous hypercortisolism.

Animals

Two hundred one client‐owned dogs with spontaneous hypercortisolism.

Methods

Retrospective study. Pre‐ and post‐contrast computed tomography (CT) scans of the pituitary and adrenal glands were performed in dogs with confirmed hypercortisolism.

Results

In dogs with dexamethasone‐suppressible hypercortisolism (122/201), 78 dogs (64%) had an enlarged pituitary gland (median pituitary height/brain area [P/B], 0.43 × 10⁻² mm⁻¹; range, 0.32‐1.21 × 10⁻² mm⁻¹). Two of these 78 dogs had concurrent adrenal lesions. In the remaining dogs (44/122; 36%), the pituitary gland was not enlarged. In the dexamethasone‐resistant group (79/201), the pituitary gland was enlarged in 47 dogs (59%; median P/B, 0.57 × 10⁻²; range, 0.32‐1.50 × 10⁻² mm⁻¹). Eight of these 47 dogs (17%) had concurrent adrenal lesions. In the remaining 32 dexamethasone‐resistant dogs (41%), the pituitary gland was not enlarged. Among them, 27 dogs had adrenal lesions and suppressed ACTH concentrations consistent with adrenal‐dependent hypercortisolism and 5 dogs were diagnosed with pituitary‐dependent hypercortisolism.

Conclusions and Clinical Importance

Concurrent pituitary and adrenal lesions were present in 5% of all dogs with hypercortisolism and in 10% of the dexamethasone‐resistant dogs. Diagnostic imaging of both pituitary and adrenal glands should be included in the diagnostic evaluation of every dog with spontaneous hypercortisolism to obtain information needed for estimation of prognosis and choosing the optimal treatment.

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.

Immunohistochemical Evaluation of Canine Pituitary Adenomas Obtained by Transsphenoidal Hypophysectomy

Hypophysectomy specimens from 16 dogs with pituitary adenoma were evaluated with periodic acid-Schiff (PAS), reticulin, and immunohistochemistry for adrenocorticotrophic hormone (ACTH), melanocyte stimulating hormone (MSH), growth hormone (GH), and Ki-67. The reticulin network was obliterated in all adenomas. One adenoma expressed ACTH and GH. Eight corticotroph adenomas were basophilic to chromophobic, and PAS- and ACTH-positive. Seven melanotroph adenomas were distinguished from corticotroph adenomas by expression of MSH. Pituitary-dependent hypercortisolism was diagnosed in 5 of 8 dogs with corticotroph and 4 of 7 with melanotroph adenoma. Pituitary height/brain area (P/B) ratio was elevated in all dogs. Previous canine hypophysectomy studies suggested that melanotroph adenomas were larger and carried a worse prognosis than corticotroph adenomas; however, in this study, corticotroph adenomas in comparison to melanotroph adenomas were larger (median P/B ratio: 1.06 versus 0.76), more proliferative (median Ki-67 index: 9.47% versus 1.99%), and associated with shorter survival (median: 300 versus 793 days). Recommended immunohistochemistry for PAS-positive pituitary adenomas includes ACTH and MSH to distinguish corticotrophs from melanotrophs and Ki-67 for proliferation index.

Transsphenoidal surgery: accuracy of an image-guided neuronavigation system to approach the pituitary fossa (sella turcica)

OBJECTIVE

To determine the accuracy of locating the pituitary fossa with the Brainsight neuronavigation system by determining the mean target error of the rostral (tuberculum sellae) and caudal (dorsum sellae) margins of the pituitary fossa.

STUDY DESIGN

Experimental cadaveric study.

ANIMALS

Ten canine cadavers.

METHODS

Computed tomography (CT) and MRI were performed on each cadaver with fiducials in place. Images were saved to the neuronavigation computer and used to plan the drilling approach. The cadavers were placed in the surgical head clamp of the Brainsight system and positioned for a transsphenoidal approach. On the basis of the planning, 2 localization points were drilled, 1 each at the rostral and caudal margins of the pituitary fossa, and CT was repeated. Error was assessed from the difference in millimeters between the targets identified during Brainsight planning and the actual location of the 2 points drilled on each cadaver skull as identified by postdrilling CT.

RESULTS

The rostral and caudal margins of the pituitary fossa provided 2 target points per cadaver. The median target error (interquartile range) for all target sites (n = 20) was 3.533 mm (range, 2.013-4.745).

CONCLUSION

This stereotactic system allowed the surgeon to locate the rostral and caudal margins of the pituitary fossa with clinically acceptable accuracy and confidence.

CLINICAL SIGNIFICANCE

Using the Brainsight neuronavigation system for localization during transsphenoidal hypophysectomy may decrease morbidity and surgical time.

Transsphenoidal Surgery for Pituitary Tumors and Other Sellar Masses

Transsphenoidal surgery is an option for dogs and cats with functional and nonfunctional pituitary masses or other sellar and parasellar masses. An adrenocorticotropic hormone-secreting tumor causing Cushing disease is the most common clinically relevant pituitary tumor in dogs, and the most common pituitary tumor seen in cats is a growth hormone-secreting tumor causing acromegaly. Transsphenoidal surgery can lead to rapid resolution of clinical signs and provide a cure for these patients. Because of the risks associated with this surgery, it should only be attempted by a cohesive pituitary surgery group with a sophisticated medical and surgical team.

Lack of Ubiquitin Specific Protease 8 (USP8) Mutations in Canine Corticotroph Pituitary Adenomas

Purpose

Cushing’s disease (CD), also known as pituitary-dependent hyperadrenocorticism, is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary tumours. Affected humans and dogs have similar clinical manifestations, however, the incidence of the canine disease is thousand-fold higher. This makes the dog an obvious model for studying the pathogenesis of pituitary-dependent hyperadrenocorticism. Despite certain similarities identified at the molecular level, the question still remains whether the two species have a shared oncogenetic background. Recently, hotspot recurrent mutations in the gene encoding for ubiquitin specific protease 8 (USP8) have been identified as the main driver behind the formation of ACTH-secreting pituitary adenomas in humans. In this study, we aimed to verify whether USP8 mutations also play a role in the development of such tumours in dogs.

Methods

Presence of USP8 mutations was analysed by Sanger and PCR-cloning sequencing in 38 canine ACTH-secreting adenomas. Furthermore, the role of USP8 and EGFR protein expression was assessed by immunohistochemistry in a subset of 25 adenomas.

Results

None of the analysed canine ACTH-secreting adenomas presented mutations in the USP8 gene. In a subset of these adenomas, however, we observed an increased nuclear expression of USP8, a phenotype characteristic for the USP8 mutated human tumours, that correlated with smaller tumour size but elevated ACTH production in those tumours.

Conclusions

Canine ACTH-secreting pituitary adenomas lack mutations in the USP8 gene suggesting a different genetic background of pituitary tumourigenesis in dogs. However, elevated nuclear USP8 protein expression in a subset of tumours was associated with a similar phenotype as in their human counterparts, indicating a possible end-point convergence of the different genetic backgrounds in the two species. In order to establish the dog as a useful animal model for the study of CD, further comprehensive studies are needed.

Comparison of Survival Times for Dogs with Pituitary-Dependent Hyperadrenocorticism in a Primary-Care Hospital: Treated with Trilostane versus Untreated

Background

Although pituitary‐dependent hyperadrenocorticism (PDH) is one of the most common endocrinopathies in dogs, the effects of withholding treatment on survival time in dogs with PDH remain unclear.

Hypothesis/Objectives

The purpose of this study was to clarify the effects of treatment in dogs with PDH by comparing survival times between dogs treated with trilostane and untreated dogs.

Animals

Forty‐three dogs diagnosed with PDH at a primary‐care hospital in Japan between June 2009 and January 2014.

Methods

Retrospective cohort study. The medical records of dogs with PDH treated with trilostane (n = 17) or left untreated (n = 26) were reviewed retrospectively. Survival analysis at 2 years after diagnosis of PDH was performed.

Results

Median survival time for the trilostane group was not reached (95% confidence interval [CI], 443 days–not applicable) and was significantly longer than the 506 days (95% CI, 292–564 days; P = .016) for the untreated group. Multivariate Cox proportional hazards analysis (including age at diagnosis, basal cortisol concentration at diagnosis, and treatment group) only identified assignment to the untreated group (hazard ratio, 5.01; 95% CI, 1.63–15.44) as associated with increased mortality.

Conclusions and Clinical Importance

The results of this retrospective cohort study suggest that withholding treatment for dogs with PDH might be associated with a higher risk of death. This represents the largest study to date to report survival times of untreated dogs with PDH.

Dynamic computed tomography of the pituitary gland using a single slice scanner in dogs with pituitary-dependent hypercortisolism

Selective removal of the pituitary adenoma has not been advocated in dogs with pituitary-dependent hypercortisolism because the pituitary adenoma is usually not visualized on routine computed tomography (CT). Dynamic pituitary CT scanning is aimed at the detection of the pituitary flush and, indirectly, at the presence and position of the adenoma. The first aim of this retrospective study was to compare findings of a multiple slice dynamic scanning protocol with those of a single slice dynamic protocol using a single slice CT scanner. The second aim was to compare the CT findings with surgical findings, and surgical findings with histopathological findings. Computed tomography with single and multiple slice dynamic scanning protocols was performed in 86 dogs with pituitary-dependent hypercortisolism. Thirty dogs underwent transsphenoidal hypophysectomy and pituitary specimens were collected as tumor, normal, mixed and neurohypophyseal samples and processed for histology. The pituitary flush was not detected more frequent in multiple slice dynamic scanning series than in single slice dynamic scanning series. However, in non-enlarged pituitaries, the flush was seen significantly more frequently than in enlarged pituitaries. Prediction of the nature of the tissue during hypophysectomy by the surgeon was inconclusive. In conclusion, when using a single slice CT scanner, both single or multiple slice dynamic scanning protocols can be used for localization of the neurohypophyseal flush, and, indirectly, the adenoma. However, based on this study, the aim of surgery in dogs with pituitary-dependent hypercortisolism remains total adenohypophysectomy, and when the neurophypophysis is recognized, it may be left in situ.

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.

A magnetic resonance imaging-based classification system for indication of trans-sphenoidal hypophysectomy in canine pituitary-dependent hypercortisolism

OBJECTIVES

The objectives of this study were to establish a magnetic resonance imaging-based classification system for canine hyperadrenocorticism according to pituitary gland extension, determine indications for trans-sphenoidal hypophysectomy, and clarify the prognosis for each disease grade.

METHODS

A 5-point classification system (Grades 1 to 5) was developed based on tumour extension in dorsal and cranio-caudal directions. Cases were then classified as Type A: no arterial circle of Willis or cavernous sinus involvement and Type B: cases in which these blood vessels were involved.

RESULTS

Medical records and magnetic resonance imaging data of 37 cases with hyperadrenocorticism were reviewed. Thirty-three cases underwent surgery; 4 Grade 5 cases did not have appropriate indications for surgery, and other therapies were used. Complete resection was achieved for 3, 3, 22 and 1 Grade 1A, 2A, 3A and 3B cases, respectively. Resection was incomplete in 1, 1 and 2 Grade 3A, 3B and 4B cases, respectively. Remission was achieved in 29 cases. Recurrence occurred in 4 cases, all of which were classified as Grade 3.

CLINICAL SIGNIFICANCE

Dogs with Type A, Grade 1 to 3 hyperadrenocorticism had a good prognosis following trans-sphenoidal hypophysectomy. Grade 3B, 4 and 5 cases may not be suitable for this surgery.

Naturally Occurring Adrenocortical Insufficiency--An Epidemiological Study Based on a Swedish-Insured Dog Population of 525,028 Dogs

Background

Naturally occurring adrenocortical insufficiency (NOAI) in dogs is considered an uncommon disease with good prognosis with hormonal replacement treatment. However, there are no epidemiological studies with estimates for the general dog population.

Objectives

To investigate the epidemiological characteristics of NOAI in a large population of insured dogs.

Animals

Data were derived from 525,028 client‐owned dogs insured by a Swedish insurance company representing 2,364,652 dog‐years at risk (DYAR) during the period between 1995–2006.

Methods

Retrospective cohort study. Incidence rates, prevalences, and relative risks for dogs with NOAI (AI with no previous claim for hypercortisolism), were calculated for the whole dog population, and for subgroups divided by breed and sex. Mortality rates were calculated and compared in dogs with NOAI and the remaining dogs overall.

Results

In total 534 dogs were identified with NOAI. The overall incidence was 2.3 cases per 10,000 DYAR. The relative risk of disease was significantly higher in the Portuguese Water Dog, Standard Poodle, Bearded Collie, Cairn Terrier, and Cocker Spaniel compared with other breeds combined. Female dogs overall were at higher risk of developing AI than male dogs (RR 1.85; 95% CI, 1.55–2.22; P < .001). The relative risk of death was 1.9 times higher in dogs with NOAI than in dogs overall.

Conclusion and Clinical Importance

The data supports the existence of breed‐specific differences in incidence rates of NOAI in dogs.

The prognostic value of perioperative profiles of ACTH and cortisol for recurrence after transsphenoidal hypophysectomy in dogs with corticotroph adenomas

BACKGROUND

Transsphenoidal hypophysectomy is an effective treatment for dogs with pituitary-dependent hypercortisolism (PDH). However, long-term recurrence of hypercortisolism is a well-recognized problem, indicating the need for reliable prognostic indicators.

OBJECTIVES

The aim of this study was to evaluate the prognostic value of perioperative plasma ACTH and cortisol concentrations for identifying recurrence of hypercortisolism after transsphenoidal hypophysectomy.

ANIMALS

A total of 112 dogs with PDH that underwent transsphenoidal hypophysectomy met the inclusion criteria of the study.

METHODS

Hormone concentrations were measured preoperatively and 1-5 hours after surgery. Both absolute hormone concentrations and postoperative concentrations normalized to preoperative concentrations were included in analyses. The prognostic value of hormone concentrations was studied with Cox's proportional hazard analysis.

RESULTS

Median follow-up and disease-free period were 1096 days and 896 days, respectively. Twenty-eight percent of patients had recurrence, with a median disease-free period of 588 days. Both absolute and normalized postoperative cortisol concentrations were significantly higher in dogs with recurrence than in dogs without recurrence. High ACTH 5 hours after surgery, high cortisol 1 and 4 hours after surgery, high normalized ACTH 3 hours after surgery, high normalized cortisol 4 hours after surgery and the random slope of cortisol were associated with a shorter disease-free period.

CONCLUSIONS AND CLINICAL IMPORTANCE

Individual perioperative hormone curves provide valuable information about the risk of recurrence after hypophysectomy. However, because no single cutoff point could be identified, combination with other variables, such as the pituitary height/brain area (P/B) ratio, is still needed to obtain a good estimate of the risk for recurrence of hypercortisolism after hypophysectomy.

Expression and clinical relevance of paired box protein 7 and sex determining region Y-box 2 in canine corticotroph pituitary adenomas

Pituitary-dependent hypercortisolism is a common endocrinopathy in dogs, caused by an adrenocorticotrophic hormone secreting pituitary tumour of the anterior or intermediate lobe. The prognosis of intermediate lobe adenomas is worse than that of anterior lobe adenomas, indicating the possible usefulness of melanotropic markers as prognosticators. Another possible origin of pituitary adenomas is found in cancer stem cells. The aim of the present study was to investigate the expression of melanotroph specific transcription factor paired box protein 7 (Pax7) and stem cell marker and reprogramming factor sex determining region Y-box 2 (Sox2) and to relate their expression to clinical parameters. The mean ± SD of labelling index (LI) for Pax7 was 8.6% ± 21.7% in the adenomas; 1/6 controls had positive staining (LI, 15.2%). For Sox2, the LI in the adenomas was 16.9% ± 15.2% and 19.5% ± 11.6% in the controls. Pax7 expression was significantly higher in enlarged pituitaries, compared to non-enlarged pituitaries (P = 0.05), but Pax7 or Sox2 immunopositivity did not correlate to other clinical parameters such as histological diagnosis, survival time or disease-free interval. Gene expression of Pax7 target genes, such as proconvertase 2 (PC2), pro-opiomelanocortin (POMC), and dopamine D2 receptor (DRD2), was significantly lower in the adenoma samples compared to normal tissue, indicating that Pax7 signalling was not activated in adenomas. It was suggested that Pax7 and Sox2 remain interesting targets for molecular investigations into their role in pituitary tumorigenesis, but were unsuitable as clinical prognosticators in dogs.

Prognostic factors for survival in dogs with pituitary-dependent hypercortisolism treated with trilostane

Pituitary-dependent hypercortisolism (PDH) is one of the most frequent endocrinopathies in dogs, but prognostic factors are largely unknown. The aim of this retrospective case series study was to determine the prognostic value of different clinical and clinicopathological variables evaluated in dogs newly diagnosed with PDH that were subsequently treated with trilostane. Medical records from one referral centre were evaluated. Eighty-five dogs with PDH were included. The median survival time was 852 days (range 2-3210 days); 60/85 (70 per cent) and 25/85 (29 per cent) dogs survived more than one and three years, respectively. In multivariable model analysis the length of survival of older dogs (HR 1.24, 95% CI 1.09 to 1.40) and dogs with higher serum phosphate concentrations (HR 1.35, 95% CI 1.01 to 1.81) was shorter. Serum phosphate concentrations were above the reference range in 37/85 (44 per cent) of animals. Clinical signs, liver enzymes, serum cortisol concentrations of the endocrine tests, proteinuria, systolic hypertension, the presence of concomitant disorders, and the frequency of trilostane administration were not associated with survival time. Hyperphosphataemia is a common finding in dogs with newly diagnosed PDH and represents a negative prognostic factor.

Severe hyperthermia, hypernatremia, and early postoperative death after transethmoidal cavitron ultrasonic surgical aspirator (CUSA)-assisted diencephalic mass removal in 4 dogs and 2 cats

OBJECTIVE

To report clinical findings including severe hyperthermia and hypernatremia after transethmoidal Cavitron ultrasonic surgical aspirator (CUSA)-assisted diencephalic mass removal.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 4) and 2 cats.

METHODS

Medical records (1997-2003) of dogs and cats that had transethmoidal CUSA-assisted diencephalic mass removal were reviewed. Retrieved data were: history, signalment, blood work, neurologic examination findings, MRI results, histopathology, postoperative complications, pre- and postoperative medical therapy, and outcome.

RESULTS

Tumor types included: meningioma (n = 3), choroid plexus papilloma (1), astrocytoma (1), and pituitary macroadenoma (1). Median onset of hyperthermia was 3.5 hours (range: 1-6 hours) after extubation; median high temperature at onset was 40.3°C, (range: 39.6-41.7°C). Median onset of hypernatremia (median, 172 mmol/L; range: 168-196 mmol/L) was 4.5 hours (range: 1-9 hours) after extubation. Median time of death after hyperthermia was 10.5 hours (range: 6-13 hours) and after extubation was 13.5 hours (range: 11-15 hours).

CONCLUSIONS

Transethmoidal CUSA-assisted diencephalic mass removal is associated with early postoperative hyperthermia, hypernatremia, and death, and cannot be recommended.

Complete surgical removal of a very enlarged pituitary corticotroph adenoma in a dog

A 13 yr old castrated male vizsla was referred to the authors' institute because of polyuria, polydipsia, polyphagia, and weight loss. Pituitary-dependent hypercortisolism (PDH) was diagnosed by hormone testing and adrenal and pituitary imaging. Computed tomography (CT) revealed a pituitary mass measuring 21 mm in width. Medical therapy was initiated with trilostane. Despite adequate control of the hypercortisolemia, the polyuria and polydipsia persisted and the dog developed neurologic signs due to the pituitary mass effect. Pituitary transsphenoidal debulking surgery was performed and immunocytochemistry confirmed a corticotroph adenoma. The dog survived for 13 mo after surgery. Postmortem examination revealed an empty fossa without pituitary remnants and the presence of a malignant pheochromocytoma in the right adrenal gland. This case report demonstrates, for the first time, that a large pituitary adenoma in the dog may be treated successfully by pituitary surgery.

Transsphenoidal surgery using a high definition video telescope for pituitary adenomas in dogs with pituitary dependent hypercortisolism: methods and results

OBJECTIVE

To (1) establish a technique for transsphenoidal removal of pituitary adenomas in dogs with pituitary dependent hypercortisolism (PDH) using a high definition video telescope, and (2) report initial outcomes.

STUDY DESIGN

Prospective case series.

ANIMALS

Dogs with pituitary dependent hypercortisolism (PDH; n = 26) with suprasellar masses.

METHODS

Pituitary tumors were removed using a modification of a transoral transsphenoidal approach. Surgery was observed using a high definition video telescope (VITOM™) and localization of the sella was performed by drilling pilot holes in the basisphenoid bone followed by computed tomography (CT).

RESULTS

Dogs had PDH confirmed by urinary cortisol to creatinine ratio (UCCR) and endogenous ACTH assays, and tumors confirmed by MRI. There were no postoperative cerebrospinal fluid leaks, wound dehiscence, or surgical site infections. Overall postoperative mortality was 19% with no mortality observed in the last 16 dogs, indicating an initial "learning curve" followed by good surgical results. All dogs that survived the immediate postoperative period (1 week) returned to their owners in good health, on hormonal replacement therapy. Follow-up ranged from 3 to 36 months. Sustained tumor control and hormonal remission based on normalized ACTH and UCCR measurements were observed in 20/21 (95%) dogs at 1-year follow-up.

CONCLUSIONS

Modifications of a trans-oral transsphenoidal technique for surgical removal of pituitary tumors provides a safe and effective strategy for long-term remission of PDH with acceptable morbidity and mortality.

Expression stability of reference genes for quantitative RT-PCR of healthy and diseased pituitary tissue samples varies between humans, mice, and dogs

Pituitary surgery generates pituitary tissue for histology, immunohistochemistry, and molecular biological research. In the last decade, the pathogenesis of pituitary adenomas has been extensively studied in humans, and to a lesser degree in dogs, and tumor oncogenesis has been studied in knock-out mice, often by means of quantitative reversed-transcriptase PCR (RT-qPCR). A precondition of such analyses is that so-called reference genes are stably expressed regardless of changes in disease status or treatment. In this study, the expression of six frequently used reference genes, namely, tata box binding protein (tbp), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta polypeptide (ywhaz), hydroxymethylbilane synthase (hmbs), beta-2-microglobulin (b2m), succinate dehydrogenase complex subunit A (sdha), and glyceraldehyde 3 phosphate dehydrogenase 1 (gapdh), was studied in pituitary tissue (normal and adenoma) from three species (humans, mice, and dogs). The stability of expression of these reference genes differed between species and between healthy and diseased tissue within one species. Quantitative analysis based on a single reference gene that is assumed to be stably expressed might lead to wrong conclusions. This cross-species analysis clearly emphasizes the need to evaluate the expression stability of reference genes as a standard and integral aspect of study design and data analysis, in order to improve the validity of the conclusions drawn on the basis of quantitative molecular analyses.

Vitamin D status before and after hypophysectomy in dogs with pituitary-dependent hypercortisolism

Both spontaneous hypercortisolism and chronic glucocorticoid treatment are associated with osteoporosis and low circulating concentrations of 1,25-dihydroxy-vitamin D in humans. Pituitary-dependent hypercortisolism (PDH) is a common disorder in dogs, but little is known about the vitamin D status of affected dogs. Pituitary-dependent hypercortisolism in dogs can be treated effectively by hypophysectomy and subsequent hormone supplementation. Because hormone supplementation does not include GH, dogs that have undergone hypophysectomy have low circulating concentrations of GH and IGF-1, which may result in low plasma 1,25-dihydroxy-vitamin D concentrations and consequently increased parathyroid hormone secretion. The aim of this study was to determine whether dogs with PDH need vitamin D supplementation before and/or after hypophysectomy. To this end, we measured plasma concentrations of GH, IGF-1, parathyroid hormone, calcium, phosphate, and vitamin D metabolites in 12 dogs with PDH before and 8 wk after hypophysectomy and in 12 control dogs. Although plasma GH concentrations were lower in dogs with PDH than in control dogs both before and after hypophysectomy, the vitamin D status was similar. In conclusion, there is no need for vitamin D supplementation in dogs with PDH, either before or after hypophysectomy.

Ki-67 and minichromosome maintenance-7 (MCM7) expression in canine pituitary corticotroph adenomas

Pituitary-dependent hyperadrenocorticism (PDH) caused by pituitary corticotroph adenoma is a common endocrine disorder in dogs. The ratio between pituitary height and the area of the brain (P/B) has been used to evaluate the pituitary size. A P/B ratio > 0.31 indicates an enlarged pituitary, whereas a P/B ratio ≤ 0.31 indicates a nonenlarged pituitary. The aim of this study was to investigate the expression of proliferation markers Ki-67 and minichromosome maintenance-7 (MCM7) in canine corticotroph adenomas in enlarged and in nonenlarged pituitaries and to evaluate their relation with the size of canine pituitary corticotroph adenomas. Ki-67 and MCM7 expression in ACTH-positive tumor cells was determined by dual-labeling immunohistochemistry in resected corticotroph adenomas from 15 dogs with PDH. The mean ± SD Ki-67 labeling index (LI) was 0.55% ± 0.59% in corticotroph adenomas with nonenlarged pituitaries and 1.6% ± 0.6% in adenomas with enlarged pituitaries. The MCM7 LI in corticotroph adenomas with nonenlarged pituitaries and in adenomas with enlarged pituitaries was 2.9% ± 2.2% and 10.9% ± 3.7%, respectively. The Ki-67 LI and MCM7 LI were significantly greater in the adenomas with enlarged pituitaries than in the adenomas with nonenlarged pituitaries (P < 0.01 and P < 0.01, respectively). The MCM7 LI was significantly greater than the Ki-67 LI in adenomas (P < 0.01). The Ki-67 LI was positively correlated with the MCM7 LI (r = 0.820, P < 0.01), and the P/B ratio was positively correlated with the Ki-67 LI (r = 0.560, P = 0.03) and the MCM7 LI (r = 0.854, P < 0.01). In conclusion, canine corticotroph adenomas in enlarged pituitaries show greater proliferation potential than do adenomas in nonenlarged pituitaries. MCM7 expression was significantly greater than Ki-67 expression in canine pituitary corticotroph adenomas. Thus, MCM7 may be superior to Ki-67 as a proliferation marker in pituitary tumors.

Expression of Ki-67, PCNA, and p27kip1 in canine pituitary corticotroph adenomas

Pituitary-dependent hypercortisolism (PDH), which is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas, is a common endocrinopathy in dogs. Dogs with non-enlarged pituitaries harboring a microadenoma have a better prognosis than those with enlarged pituitaries. The aim of this study was to investigate the expression of the proliferation markers Ki-67 and proliferating cell nuclear antigen (PCNA) and the cell-cycle inhibitor p27kip1 in corticotroph adenomas in enlarged and non-enlarged pituitaries. The expression of Ki-67, PCNA, and p27kip1 was analyzed by immunohistochemical staining of 17 pituitary adenoma samples harvested during pituitary surgery in dogs with PDH. The labeling index was calculated by counting the number of immunopositive cells per 1,000 cells. The mean (+/- standard deviation) labeling index for Ki-67 was 8.4%+/-14.2% for the group with enlarged pituitaries, and 8.8%+/-5.5% for the group with non-enlarged pituitaries; that for PCNA was 35.5%+/-12.2% and 37.0%+/-15.5%; and that for p27kip1 was 29.3%+/-22.6% and 42.5%+/-27.9%, respectively. No significant differences in Ki-67, PCNA, and p27kip1 labeling indices were found between enlarged and non-enlarged pituitaries. However, a trend toward significance was observed when comparing the expression of p27kip1 in enlarged pituitaries versus normal pituitary tissue. It is concluded that Ki-67 and PCNA are not useful as proliferative markers for studying the pathobiology of pituitary corticotroph adenomas in dogs.

Corticotroph adenoma in the dog: pathogenesis and new therapeutic possibilities

The corticotrophinoma, causing pituitary dependent hypercortisolism, represents the highest percentage of pituitary tumours in the dog. The mechanism by which it develops is currently unknown and two theories are postulated: the hypothalamic and the monoclonal. It is not clear either what factors are involved in the tumour genesis; nevertheless, firm candidates are the Rb1 gene, proteins p27, p21 and p16, as are also defects in the glucocorticoid receptor and Nur77/Nurr1. The role of BMPs remains to be evaluated in greater depth. Although at present the chosen treatment in human is surgical, there are various pharmacological treatments already in use that have favourable results and others, still under research, also showing promising results.

Computed tomography and low-field magnetic resonance imaging of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism: 11 cases (2001-2003)

OBJECTIVE

To compare the results of computed tomography (CT) and magnetic resonance imaging (MRI) of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism (PDH) caused by histologically confirmed pituitary adenoma.

DESIGN

Retrospective case series.

ANIMALS

11 dogs with PDH that underwent transsphenoidal hypophysectomy.

PROCEDURES

Medical records of dogs examined between January 2001 and March 2003 were reviewed. Dogs were included in this study if they had clinical signs of hypercortisolism at the time of admission (for which PDH was diagnosed) and underwent transsphenoidal hypophysectomy. Pre- and postcontrast CT and low-field MRI (0.2-Tesla magnet) were performed on the same day as surgery for each dog.

RESULTS

An abnormal pituitary gland was found in 7 dogs by use of MRI and in the same 7 dogs by use of CT. Significant differences were found between postcontrast CT and MR images for height, width, and length of the pituitary gland; brain area; and thickness of the sphenoid bone. However, the pituitary gland height-to-brain area ratio determined from postcontrast CT and MR images was not significantly different. The signal-to-noise ratio and contrast-to-noise ratio of pre- and postcontrast MR images were significantly higher than those of the CT images.

CONCLUSIONS AND CLINICAL RELEVANCE

Low-field MRI and dynamic CT imaging of the pituitary gland provided comparable information on the presence of pituitary adenomas in dogs with PDH.

Trilostane-induced inhibition of cortisol secretion results in reduced negative feedback at the hypothalamic-pituitary axis

Cushing's disease caused by pituitary corticotroph adenoma in dogs is usually treated by medical treatment, and the efficacy of this treatment has been reported. However, controversy remains as to whether reduced negative feedback through the inhibition of cortisol secretion, similar to Nelson's syndrome, may appear as an adverse effect. The purpose of this study was to investigate the effect of reduced negative feedback through the inhibition of cortisol secretion by daily trilostane administration on the pituitary-adrenal axis in clinically normal dogs. Dogs were administered 5mg/kg trilostane twice a day every day for 8 weeks (n=8) or 16 weeks (n=3). After the initiation of trilostane administration, plasma adrenocorticotropic hormone (ACTH) concentrations were increased remarkably. As assessed by magnetic resonance imaging (MRI) during administration, the pituitary became enlarged. After trilostane administration, the cytoplasmic areas of the pituitary corticotrophs were increased and the ratio of pituitary corticotrophs to all cells in the anterior lobe was greater in the trilostane-treated dogs than that in untreated animals. In addition, histological examinations revealed bilateral adrenal cortical hyperplasia. Using real-time PCR quantification, the expression of proopiomelanocortin (POMC) mRNA in the pituitary and ACTH receptor (ACTH-R) mRNA in the adrenal gland was greater in the dogs treated with trilostane than in untreated dogs. These results indicate that reduced negative feedback induced hyperfunction of the pituitary corticotrophs and pituitary enlargement in healthy dogs. These changes suggest that the inhibition of cortisol secretion by trilostane may increase the risk for accelerating the growth of corticotroph adenomas in dogs with Cushing's disease.

Expression and functional analysis of dopamine receptor subtype 2 and somatostatin receptor subtypes in canine cushing's disease

Cushing's disease (CD) is a severe disorder characterized by chronic hypercortisolism due to an ACTH-secreting pituitary adenoma. Transsphenoidal adenomectomy is the treatment of choice in humans with CD, but recurrences occur frequently. Finding an effective and safe medical treatment for CD may improve long-term clinical outcome. The recent demonstration of expression of somatostatin receptor subtypes (mainly sst5) and dopamine receptor subtype 2 (D2) in human corticotroph adenomas offers the possibility for medical treatment of CD with novel somatostatin analogs and dopamine agonists. Investigation of the effects of these drugs is hampered by the low incidence of CD in humans. Interestingly, CD is a frequent disorder in dogs with striking clinical similarities with CD in humans. Therefore, we investigated the expression and functional role of D2 and somatostatin receptors in corticotroph adenoma cells from 13 dogs with active CD that underwent therapeutic hypophysectomy and normal anterior pituitary cells from five dogs. Quantitative RT-PCR and immunohistochemistry revealed that both in CD and normal anterior pituitary, sst2 was the predominant receptor subtype expressed, whereas D2 was modestly expressed and sst5 was expressed only at very low levels. In primary cultures of canine adenomas (n = 7), the sst2-preferring agonist octreotide also showed the strongest ACTH-suppressive effects. In conclusion, canine corticotroph adenomas provide an interesting model to study CD, but differences in somatostatin and dopamine receptor expression between humans and dogs should be taken into account when using dogs with CD as a model to evaluate efficacy of novel somatostatin analogs and dopamine agonists for human CD.