Effect of octreotide on plasma concentrations of glucose, insulin, glucagon, growth hormone, and cortisol in healthy dogs and dogs with insulinoma

Use of octreotide for the treatment of protein-losing enteropathy in dogs: Retrospective study of 18 cases

BACKGROUND

More than 50% of dogs with protein-losing enteropathy (PLE) fail to respond to standard therapies. Octreotide, a somatostatin analogue, is used in cases of intestinal lymphangiectasia (IL) in humans with some success.

OBJECTIVES

Describe the use of octreotide in dogs with PLE including reason for and details of prescription, adverse effects, and apparent response.

ANIMALS

Eighteen dogs with PLE, 13 with histopathology available. Ninety-two percent (12/13) had IL diagnosed on biopsy. All 13 dogs had intestinal inflammatory infiltrates noted.

METHODS

Multicenter, retrospective, descriptive study. Cases were volunteered for inclusion by individual attending veterinarians who reported the use of octreotide in cases of PLE.

RESULTS

In 16/18 (89%) cases octreotide was prescribed to PLE dogs with a clinical suspicion or confirmed diagnosis of IL that were refractory to standard therapies. Median serum albumin at the time of octreotide prescription was 1.7 g/dL (range, 1.0-3.1 g/dL). The median dose of octreotide prescribed was 20 μg/kg, SQ, daily with a range of 4-39 μg/kg, SQ, daily. Adverse effects were noted in 3/18 (17%, 95% CI [4%, 41%]) of dogs; discontinuation of the drug was necessary in 1 dog. Improvement in clinical signs was noted in 6/12 (50%, 95% CI [21%, 79%]).

CONCLUSIONS AND CLINICAL IMPORTANCE

Octreotide was most commonly prescribed to dogs with PLE and suspected or confirmed IL that had failed to respond to standard therapies. Though a benefit to PLE dogs cannot be confirmed, octreotide was well tolerated by the majority of dogs at the doses prescribed in this study.

Toceranib phosphate in the management of canine insulinoma: A retrospective multicentre study of 30 cases (2009-2019)

BACKGROUND

Insulinomas are the most common tumour of the endocrine pancreas in dogs. These malignant tumours have a high metastatic rate and limited chemotherapeutic options. The multi-receptor tyrosine kinase inhibitor sunitinib malate has benefit in the treatment of metastatic insulinoma in people. Toceranib phosphate, an analogous veterinary agent, may provide benefit for dogs.

METHODS

A retrospective study describing the extent and duration of clinical outcomes and adverse events (AEs) in dogs diagnosed with insulinoma and receiving toceranib.

RESULTS

Records for 30 dogs diagnosed with insulinoma and having received toceranib were identified from a medical record search of five university and eight referral hospitals. The median progression-free interval and overall survival time were 561 days (95% confidence interval (CI): [246, 727 days]) and 656 days (95% CI: [310, 1045 days]), respectively. Of the dogs for which the canine Response evaluation criteria for solid tumours tool could be applied, the majority (66.7%) showed either a complete response, partial response or stable disease. Time to clinical progression was associated with prior intervention and type of veterinary practice. Larger dogs were at increased risk for disease progression and death. No novel AEs were reported.

CONCLUSIONS

Most dogs diagnosed with insulinoma and receiving toceranib appeared to have a clinical benefit. Randomised, prospective studies are needed to better elucidate and objectively quantify the potential effect and survival benefit of toceranib therapy for management of insulinoma in dogs.

Clinical recovery of 5 dogs from amatoxin mushroom poisoning using an adapted Santa Cruz protocol for people

OBJECTIVE

To describe the clinical course, treatment, and outcome of 5 dogs following ingestion of toxic Amanita spp. mushrooms containing amatoxins using an adapted version of the Santa Cruz protocol developed for people.

CASE SERIES SUMMARY

Five dogs were presented with clinical signs compatible with amanitin toxicity with witnessed ingestion noted in 3 of 5 dogs. Clinical findings included acute onset vomiting and diarrhea, lethargy, and hepatopathy including signs of fulminant hepatic failure (increased liver enzyme activities, hyperbilirubinemia, prolonged clotting times, and hypoglycemia were noted among these cases). Urine toxicological screening confirmed the presence of Amanita toxins in 4 cases with expert mycologist speciation in the fifth. Core interventions included percutaneous biliary drainage, use of octreotide, and early nil per os orders. All dogs survived to discharge with this treatment strategy.

NEW OR UNIQUE INFORMATION PROVIDED

This case series describes the use of a modified version of the Santa Cruz protocol to address amatoxin-induced fulminant hepatic failure in dogs. The protocol was safe, well tolerated, and all patients made a full clinical recovery.

Suspected congenital hyperinsulinism in a Shiba Inu dog

A 3‐month‐old male intact Shiba Inu dog was evaluated for a seizure disorder initially deemed idiopathic in origin. Seizure frequency remained unchanged despite therapeutic serum phenobarbital concentration and use of levetiracetam. The dog was documented to be markedly hypoglycemic during a seizure episode on reevaluation at 6 months of age. Serum insulin concentrations during hypoglycemia were 41 U/μL (reference range, 10‐29 U/μL). The dog was transitioned to 4 times per day feeding, diazoxide was started at 3.5 mg/kg PO q8h, and antiepileptic drugs were discontinued. No clinically relevant abnormalities were identified on bicavitary arterial and venous phase contrast computed tomographic imaging. The dog remained seizure‐free and clinically normal at 3 years of age while receiving 5.5 mg/kg diazoxide PO q12h and twice daily feeding. Seizures later occurred approximately twice per year and after exertion, with or without vomiting of a diazoxide dose. Blood glucose curves and interstitial glucose monitoring were used to titrate diazoxide dose and dosing interval. Congenital hyperinsulinism is well recognized in people but has not been reported in veterinary medicine.

Diagnosis of insulinoma in a Maine Coon cat

Case summary

A 14-year-old male neutered Maine Coon cat presented with a 6-month history of polyphagia and one recent episode of tremors and weakness. Blood work revealed profound hypoglycemia and results of a paired insulin glucose test were consistent with an insulinoma. Abdominal ultrasound revealed a solitary pancreatic mass, and results of a fine-needle aspirate (FNA) gave further support for the location of the neuroendocrine tumor. After unsuccessful medical management of the hypoglycemia, the mass was surgically removed. Immunohistochemistry confirmed that it was an insulinoma. At the time of writing, the patient had been in clinical remission for 9 months.

Relevance and novel information

Feline insulinomas are rare and there is very little information on their behavior, clinical course and histologic characteristics. This is the first reported case of an insulinoma in a Maine Coon cat and the first to describe results of an ultrasound-guided FNA of the mass. In addition, the progression of disease, histopathology and immunohistochemistry results add to the currently minimal database for feline insulinomas.

Comparative pathophysiology and management of protein-losing enteropathy

Protein‐losing enteropathy, or PLE, is not a disease but a syndrome that develops in numerous disease states of differing etiologies and often involving the lymphatic system, such as lymphangiectasia and lymphangitis in dogs. The pathophysiology of lymphatic disease is incompletely understood, and the disease is challenging to manage. Understanding of PLE mechanisms requires knowledge of lymphatic system structure and function, which are reviewed here. The mechanisms of enteric protein loss in PLE are identical in dogs and people, irrespective of the underlying cause. In people, PLE is usually associated with primary intestinal lymphangiectasia, suspected to arise from genetic susceptibility, or “idiopathic” lymphatic vascular obstruction. In dogs, PLE is most often a feature of inflammatory bowel disease (IBD), and less frequently intestinal lymphangiectasia, although it is not proven which process is the true driving defect. In cats, PLE is relatively rare. Review of the veterinary literature (1977‐2018) reveals that PLE was life‐ending in 54.2% of dogs compared to published disease‐associated deaths in IBD of <20%, implying that PLE is not merely a continuum of IBD spectrum pathophysiology. In people, diet is the cornerstone of management, whereas dogs are often treated with immunosuppression for causes of PLE including lymphangiectasia, lymphangitis, and crypt disease. Currently, however, there is no scientific, extrapolated, or evidence‐based support for an autoimmune or immune‐mediated mechanism. Moreover, people with PLE have disease‐associated loss of immune function, including lymphopenia, severe CD4+ T‐cell depletion, and negative vaccinal titers. Comparison of PLE in people and dogs is undertaken here, and theories in treatment of PLE are presented.

Long-Term Survival and Glycemic Control with Toceranib Phosphate and Prednisone for a Metastatic Canine Insulinoma

Canine insulinoma is a highly metastatic neoplasm that is associated with a guarded to poor prognosis in dogs with distant metastases. A median survival of 6 mo has been reported for dogs with metastatic insulinoma. The dog in this report, diagnosed with stage III pancreatic insulinoma, had long-term glycemic control with survival of over 24 mo while receiving prednisone and toceranib phosphate after partial pancreatectomy. Toceranib phosphate has been shown to be an efficacious therapy for canine mast cell tumors with increasing evidence that it may be beneficial in the medical management of neuroendocrine tumors.

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.

Pathophysiology and aetiology of hypoglycaemic crises

Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications.

Constant rate infusion of glucagon as an emergency treatment for hypoglycemia in a domestic ferret (Mustela putorius furo)

CASE DESCRIPTION

A 3-year-old female domestic ferret (Mustela putorius furo) with an insulinoma was treated because of a hypoglycemic crisis prior to scheduled pancreatectomy with concurrent nodulectomy.

CLINICAL FINDINGS

Previously, the ferret had clinical signs of lethargy and hind limb weakness; at that time, blood glucose concentration was low, and a tentative diagnosis (subsequently confirmed) of insulinoma was made. Prednisolone treatment (0.3 mg/kg [0.14 mg/lb], PO, q 12 h) did not improve clinical signs; the dosage was gradually increased over a 1-month course (1.8 mg/kg [0.82 mg/lb], PO, q 12 h) and maintained for 10 days. Overall, the treatment was ineffective, and the ferret remained lethargic and developed inappetence. At a reevaluation, the ferret had severe weakness and nonresponsiveness nearing a comatose state. Standard treatment with dextrose (1 mL of 50% solution, IV), and dexamethasone (1 mg/kg [0.45 mg/lb], SC) was administered with resultant improvement in mentation. The ferret was discharged from the hospital and then returned 3 days later for stabilization prior to pancreatectomy with concurrent nodulectomy.

TREATMENT AND OUTCOME

The day before surgery, the ferret was administered a glucagon constant rate infusion at a rate of 15 ng/kg/min (6.8 ng/lb/min), which resulted in an increase in blood glucose concentration to a euglycemic state and resolution of clinical signs of hypoglycemia.

CLINICAL RELEVANCE

As illustrated by the case described in this report, a glucagon constant rate infusion can be used successfully for the emergency treatment of hyperinsulinemic-hypoglycemic crisis in insulinomic ferrets.

Prolonged survival in an aged Labrador retriever with a metastatic insulinoma

This case report highlights an unusually prolonged, asymptomatic, disease-free interval in an aged male Labrador retriever that underwent partial pancreatectomy for a functionally active pancreatic insulinoma with histologically confirmed hepatic metastasis. The patient developed pancreatitis and nonseptic suppurative peritonitis 24 hr after surgical resection of the insulinoma and was managed medically until discharge. Three mo after surgery, the dog was diagnosed with exocrine pancreatic insufficiency (EPI) that was effectively managed with parenteral pancreatic enzymes. Due to normal glucose levels 3 mo postsurgically, liver samples from the initial surgery were resubmitted for immunohistochemistry. Results confirmed insulinoma metastasis with insulin expression. Ten mo postsurgically, the blood glucose was normal and serum insulin levels were slightly above the upper reference limit. The first hypoglycemic episode was documented 23 mo postoperatively, which was effectively managed with prednisone. The cause for the prolonged disease remission and survival was unknown, but was possibly a result of pancreatitis and peritonitis, partial spontaneous regression of metastatic lesions, or idiopathic. Despite life-threatening postoperative complications, this patient enjoyed a profoundly longer than expected survival. This case highlights the importance of removing the primary tumor (insulinoma) despite the presence of metastatic disease.

Insulinoma in Dogs: A Review

Insulinomas are rare malignant functional pancreatic tumors of the β cells that retain the ability to produce and secrete insulin. Insulinomas are the most common pancreatic neuroendocrine tumor in dogs that can induce a variety of clinical signs that result from hypoglycemia and secondary neuroglycopenic and adrenergic effects. Diagnosis and treatment is considered challenging, and the prognosis can be extremely variable depending on the therapeutic choices. This review aims to summarize and update classic knowledge with current trends in the diagnosis, treatment, and prognosis of insulinomas.

Octreotide for the treatment of systemic lupus erythematosus: clinical effects and an in vitro study on its therapeutic mechanism

Increased serum growth hormone (GH), together with high expression of growth hormone receptor on peripheral blood mononuclear cells (PBMCs), correlates with systemic lupus erythematosus (SLE) activity, suggesting that modulation of GH signaling may affect SLE activity. We explored the effects of octreotide (OCT), an analog of somatostatin that suppresses the release of GH, in SLE. The objectives of the study were to investigate effects of OCT on the proliferative capacity and cytokine expression of PBMCs from patients with SLE and to investigate therapeutic effects of OCT in patients with SLE. PBMCs from 13 active/inactive SLE patients and 11 controls were pretreated with or without GH and cultured with OCT. The proliferation of PBMCs was assessed by MTT assay and cytokines were quantified by ELISA. We compared the clinical response of 12 patients with SLE treated with OCT (100 µg twice daily) with 12 patients treated with prednisone over three months. OCT inhibited PBMC proliferation in a dose-dependent manner and decreased the secretion of interleukin-6 (IL-6), interleukin-10 (IL-10), and interferon-gamma (IFN-γ). Patients treated with OCT demonstrated improvements in SLEDAI, dsDNA titer, complement levels, and erythrocyte sedimentation rate (ESR). OCT inhibited PBMC proliferation and PBMC secretion of IL-6, IL-10 and IFN-γ stimulated by GH. Treatment of patients with OCT resulted in clinical improvement in SLE.

Determination of octreotide and assessment of matrix effects in human plasma using ultra high performance liquid chromatography-tandem mass spectrometry

A selective UHPLC-MS/MS method for determination of the therapeutic peptide octreotide in human plasma was developed and validated. This assay used a UHPLC C(18) column with 1.7 μm particle size for efficient separation and an ion-exchange SPE for selective extraction. Octreotide and its labeled internal standard, [(13)C(6)Phe(3)] octreotide, were extracted from human plasma using a simple Oasis® WCX μElution SPE method and analyzed with a total chromatographic run time of 7.5 min. Matrix effects were studied during method development by direct monitoring of representative phospholipids. On-line removal of phospholipids using column switching and pre-column back-flushing was carried out to trap and remove any residual phospholipid matrix interferences. The UHPLC column provided baseline separation between the analyte and matrix peaks. The chromatographic conditions yielded optimal retention and excellent peak shape for both the analyte and internal standard. The assay was linear in the concentration range of 0.025-25.0 ng/ml, inter- and intra-assay precision and accuracy were within 6.1% and ±1.93%, respectively. Recovery was ∼73%. Post-extraction addition experiments showed that matrix effects were less than 4%. This method for octreotide in human plasma has been validated and utilized to support of clinical pharmacokinetic studies.

Portal hypertension: pathophysiology, diagnosis, and treatment

Portal hypertension (PH) is the result of increased vascular resistance in the portal circulation, increased portal venous blood flow, or both. In veterinary medicine, where portal pressure is seldom measured directly, the diagnosis of PH often is inferred from identification of associated complications including multiple acquired portosystemic shunts, ascites, and hepatic encephalopathy. Likewise, treatment of PH primarily is aimed at controlling these complications. The goal of this review is to provide an update on the pathophysiology, diagnosis, and treatment of PH. The review draws from information in the veterinary hepatology literature, reviews, and consensus statements in human hepatology and the literature on experimental models of PH.

Effect of SOM230 (pasireotide) on corticotropic cells: action in dogs with Cushing's disease

SOM230 (pasireotide) is a multiligand somatostatin (SRIF) analog able to bind to somatostatin receptor (SSTR) subtypes 1, 2, 3 and 5, and trigger antisecretory and antiproliferative signaling cascades. Canines have become in vivo models to test the pharmacological treatment of corticotropinomas because they frequently develop Cushing's disease in a spontaneous manner, due to adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. Different levels of expression of SSTR2 and SSTR5 have been shown in both mouse AtT20 cells and canine tumoral corticotropinoma cells. The objective of this study was to evaluate whether SOM230 controls both tumor cell growth and hormone synthesis, therefore controlling the disease. SOM230 was tested in dogs suffering from Cushing's disease (10 animals were treated continuously during 6 months, and another 10 were treated with 3 cycles consisting of 2 months of treatment followed by a 2-month rest period). A significant decrease in ACTH, urinary cortisol creatinine ratio, adenoma size (magnetic nuclear resonance) and improvement of clinical signs were obtained, without side effects. AtT20 cells treated with SOM230 suppressed pro-opiomelanocortin (POMC) promoter activity through SSTR2, via the G(i) α-subunit, and reduced Nur77/Nurr1 transcriptional activity. We conclude that SOM230, in addition to its well-described antisecretory effects, inhibits, as shown in AtT20 cells, ACTH synthesis at the POMC transcriptional level, an effect mediated mainly through SSTR2, and limits tumor growth. The controlled Cushing's disease in the dogs that received the treatment indicates that SOM230 has a potential therapeutic use in humans suffering from Cushing's disease.

Functional and morphological changes in the adenohypophysis of dogs with induced primary hypothyroidism: loss of TSH hypersecretion, hypersomatotropism, hypoprolactinemia, and pituitary enlargement with transdifferentiation

From case studies in humans it is known that primary hypothyroidism (PH) may be associated with morphological and functional changes of the pituitary. There is no insight into the time scale of these changes. In this study, seven beagle dogs were followed up for 3 years after the induction of primary hypothyroidism. Three of these dogs were followed up for another 1.5 years while receiving l-thyroxine. Adenohypophyseal function was investigated at 2-month intervals with the combined intravenous injection of CRH, GHRH, GnRH, and TRH, and measurement of the plasma concentrations of ACTH, GH, LH, PRL, and TSH. In addition, after 2 years of hypothyroidism a single TRH-stimulation test and a somatostatin test were performed, with measurements of the same pituitary hormones. Every 6 months the pituitary gland was visualized by computed tomography (CT). Induction of PH led to high plasma TSH concentrations for a few months, where after concentrations gradually declined to values no longer significantly different from pre-PH values. A blunted response to stimulation of TSH release preceded this decline. Basal plasma GH concentrations increased during PH and there was a paradoxical hyperresponsiveness to TRH stimulation. Basal GH concentrations remained elevated and returned only to low values during l-thyroxine treatment. Basal PRL concentrations decreased significantly during PH and normalized after several months of l-thyroxine treatment. The pituitary gland became enlarged in all dogs. Histomorphology and immunohistochemical studies in 4 dogs, after 3 years of PH, revealed thyrotroph hyperplasia, large vacuolated thyroid deficiency cells, and decreased numbers of mammotrophs. Several cells stained for both GH and TSH. In conclusion, with time PH led to a loss of the TSH response to low T4 concentrations, hypersecretion of GH, and hyposecretion of PRL. The enlarged pituitaries were characterized by thyrotroph hyperplasia, large vacuolated thyroid deficiency cells, and double-staining cells, which are indicative of transdifferentiation.

Metabolic epidermal necrosis in a dog associated with pancreatic adenocarcinoma, hyperglucagonaemia, hyperinsulinaemia and hypoaminoacidaemia

A case of metabolic epidermal necrosis associated with a pancreatic carcinoma is described. Normoglycaemia, reduced serum fructosamine, and hypoaminoacidaemia were identified. Hyperinsulinaemia and hyperglucagonaemia were documented. Immunohistochemistry documented strong tumour expression of both insulin and glucagon supporting combined paraneoplastic production of both hormones by the tumour. Enteral protein and fatty acid supplementation and parenteral amino acid supplementation proved ineffective. Metastasis to regional lymph nodes was identified and the patient was euthanased.