Pasireotide Long-Acting Release Treatment for Diabetic Cats with Underlying Hypersomatotropism

Expression of somatostatin receptors in canine and feline meningioma

OBJECTIVES

The standard treatment for canine and feline meningiomas includes radiotherapy, surgical excision or combined therapy. However, new therapeutic approaches are required due to the possible recurrence or progression of meningiomas despite initial therapy. Adjunctive therapy with synthetic long-acting somatostatin (SST) analogues has been described in humans with SST-expressing tumours. The expression of SST receptors (SSTRs) by feline meningiomas is currently unknown, and there are little data about canine meningiomas. We hypothesized that SSTR is expressed by canine and feline meningiomas (S1).

METHODS

Seven canines and 11 felines with histologically confirmed meningiomas underwent STTR screening. RNA expressions of SSTR1, SSTR2, SSTR3 and SSTR5 (canine) and SSTR1-SSTR 5 (feline) in fresh frozen and formalin-fixed and paraffin-embedded (FFPE) samples were investigated using real-time (RT)-qPCR. The expression of SSTR1 and SSTR2 in FFPE samples was evaluated using immunohistochemistry (IHC). The specificity of applied antibodies for canine and feline species was confirmed by western blotting.

RESULTS

In canine meningiomas (n = 7), RNA expression of SSTR1, SSTR2 and SSTR5 was detected in all samples; SSTR3 RNA expression was detected in only 33% of samples. In feline meningiomas (n = 12), RNA expression of SSTR1, SSTR4, SSTR5 and SSTR2 was detected in 91%, 46%, 46% and 36% of samples, respectively; SSTR3 was not expressed. Overall, the detection rate was lower in FFPE samples. IHC revealed the expression of SSTR1 and SSTR2 in all samples from both species. However, it is important to exercise caution when interpreting IHC results due to the presence of diffuse background staining.

CONCLUSIONS

SSTRs are widely expressed in canine and feline meningiomas, thereby encouraging further studies investigating SSTR expression to conduct trials about the effect of adjunctive therapy with long-acting SST-analogues.

Acromegaly in humans and cats: Pathophysiological, clinical and management resemblances and differences

OBJECTIVE

Acromegaly is a disorder associated with excessive levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). In general, GH/IGF-1 excess leads to morphologic craniofacial and acral changes as well as cardiometabolic complications, but the phenotypic changes and clinical presentation of acromegaly differ across species. Here, we review the pathophysiology, clinical presentation and management of acromegaly in humans and cats, and we provide a systematic comparison between this disease across these different species.

DESIGN

A comprehensive literature review of pathophysiology, clinical features, diagnosis and management of acromegaly in humans and in cats was performed.

RESULTS

Acromegaly is associated with prominent craniofacial changes in both species: frontal bossing, enlarged nose, ears and lips, and protuberant cheekbones are typically encountered in humans, whereas increased width of the head and skull enlargement are commonly found in cats. Malocclusion, prognathism, dental diastema and upper airway obstruction by soft tissue enlargement are reported in both species, as well as continuous growth and widening of extremities resulting in osteoarticular compromise. Increase of articular joint cartilage thickness, vertebral fractures and spine malalignment is more evident in humans, while arthropathy and spondylosis deformans may also occur in cats. Generalized organomegaly is equally observed in both species. Other similarities between humans and cats with acromegaly include heart failure, ventricular hypertrophy, diabetes mellitus, and an overall increased cardiometabolic risk. In GH-secreting pituitary tumours, local compressive effects and behavioral changes are mostly observed in humans, but also present in cats. Cutis verticis gyrata and skin tags are exclusively found in humans, while palmigrade/plantigrade stance may occur in some acromegalic cats. Serum IGF-1 is used for acromegaly diagnosis in both species, but an oral glucose tolerance test with GH measurement is only useful in humans, as glucose load does not inhibit GH secretion in cats. Imaging studies are regularly performed in both species after biochemical diagnosis of acromegaly. Hypophysectomy is the first line treatment for humans and cats, although not always available in veterinary medicine.

CONCLUSION

Acromegaly in humans and cats has substantial similarities, as a result of common pathophysiological mechanisms, however species-specific features may be found.

Feline Comorbidities: Hypersomatotropism-induced diabetes in cats

PRACTICAL RELEVANCE

Diabetes mellitus is the second-most common feline endocrinopathy, affecting an estimated 1/200 cats. While the underlying causes vary, around 15-25% of cats with diabetes mellitus develop the condition secondarily to progressive growth hormone (GH)-induced insulin resistance. This typically results in a form of diabetes that is challenging to manage, whereby the response to insulin is very variable or high doses are required to achieve even minimal diabetic control.

CLINICAL CHALLENGES

Although uncontrolled chronic excessive GH may result in phenotypic changes that raise suspicion for acromegaly, many cats with hypersomatotropism (HST) do not have these changes. In these situations, a clinician's index of suspicion may be increased by the presence of less dramatic changes such as marked polyphagia, stertor or uncontrolled diabetes mellitus. The current diagnostic test of choice is demonstration of a markedly increased serum insulin-like growth factor 1 (IGF1) concentration, but some affected cats will have only a marginal increase; additionally, chronic insulin administration in cats results in an increase in serum IGF1, making the diagnosis less clear cut and requiring additional confirmatory tests.

EVIDENCE BASE

Over the past two decades, HST has increasingly been recognised as an underlying cause of diabetes mellitus in cats. This review, which focuses on diagnosis and treatment, utilises data from observational studies, clinical trials and case series, as well as drawing on the experience of the authors in managing this condition.

Transsphenoidal hypophysectomy for the treatment of hypersomatotropism secondary to a pituitary somatotroph adenoma in a dog

Pituitary-dependent hypersomatotropism is rarely diagnosed in dogs and surgical treatment is not reported. A 6-year-10-month male neutered Patterdale Terrier presented with polyuria, polydipsia, progressive pharyngeal stertor, excessive hair growth and widened facial features and paws. Serum insulin-like growth factor-1 concentration via radioimmunoassay was consistent with hypersomatotropism (1783 ng/mL). A pituitary mass was identified on magnetic resonance and computed tomography imaging. Six weeks later, glucosuria, starved hyperglycemia and serum fructosamine above the reference range (467.6 μmol/L, RI 177-314) were documented, consistent with diabetes mellitus. Transsphenoidal hypophysectomy was performed under general anesthesia without complications. Pituitary histopathology identified an acidophil neoplasm, with positive immunostaining for growth hormone. Postoperatively, there was rapid resolution of clinical, biochemical and morphologic changes of hypersomatotropism with persistence of diabetes mellitus. This case demonstrates successful resolution of hypersomatotropism with ongoing diabetes mellitus in a dog after surgical treatment by transsphenoidal hypophysectomy.

Method Validation and Establishment of Reference Intervals for an Insulin-like Growth Factor-1 Chemiluminescent Immunoassay in Cats

Previously, radioimmunoassay (RIA) has been the only assay to measure insulin-like growth factor-1 (IGF-1) to diagnose hypersomatotropism (HS). Due to radiation concerns, availability, and the cost of IGF-1 RIA, validation of assays for automated analysers such as a chemiluminescent immunoassay (CLIA) is needed. The aim of this study was to validate a CLIA for measurement of feline IGF-1 (IMMULITE 2000® XPi, Siemens Medical Solutions Diagnostics, Malvern, PA, USA) compared to IGF1 RIA, establish reference interval (RI), and determine a cut-off value for diagnosis of HS in diabetic cats. Validation of assay performance included precision, linearity, and recovery studies. Right-sided RI was determined using surplus serum of 50 healthy adult cats. Surplus serum samples of diabetic cats with known IGF-1 concentration with (n = 32/68) and without HS (n = 36/68) were used for method comparison with RIA. The cut-off for diagnosis of HS was established using receiver operating characteristic (ROC) analysis. The intra-assay coefficient of variation (CV) was ≤4.7%, and the inter-assay CV was ≤5.6% for samples with low, medium, and high IGF-1 concentration. Linearity was excellent (R2 > 0.99). The correlation between CLIA and RIA was very high (rs = 0.97), with a mean negative bias for CLIA of 24.5%. The upper limit of RI was 670 ng/mL. ROC analysis showed an area under the curve of 0.94, with best cut-off for diagnosis of HS at 746 ng/mL (sensitivity, 84.4%; specificity, 97.2%). The performance of CLIA was good, and the RI and cut-off for HS diagnosis established in this study allow for CLIA to be used in routine work-up of diabetic cats.

Hypersomatotropism and Other Causes of Insulin Resistance in Cats

True insulin resistance should be differentiated from management-related difficulties (eg, short insulin duration, inappropriate insulin injection, inappropriate storage). Hypersomatotropism (HST) is the number one cause of insulin resistance in cats, with hypercortisolism (HC) occupying a more distant second place. Serum insulinlike growth factor-1 is adequate for screening for HST, and screening at the time of diagnosis, regardless of presence of insulin resistance, is advocated. Treatment of either disease centers on removal of the overactive endocrine gland (hypophysectomy, adrenalectomy) or inhibition of the pituitary or adrenal glands by using drugs such as trilostane (HC), pasireotide (HST, HC) or cabergoline (HST, HC).

Cabergoline treatment in cats with diabetes mellitus and hypersomatotropism

OBJECTIVES

The aim of this study was to evaluate the safety and efficacy of cabergoline to control hypersomatotropism (HST) and diabetes mellitus (DM) in cats.

METHODS

This was a prospective cohort study. Twenty-three cats with HST and concurrent DM were enrolled. Cats received a dose of 10 μg/kg cabergoline q48h PO for 6 months. Serum insulin-like growth factor 1 (IGF-1) and fructosamine concentrations, insulin dose and Insulin Resistance Index (IRI) were measured at the time of diagnosis of HST and at the start of cabergoline treatment (t0), and 3 months (t1) and 6 months (t2) during cabergoline treatment.

RESULTS

A decrease and normalization of serum IGF-1 concentration was observed in 35% and 26% of cats, respectively. Median IGF-1 (t0: 1350 ng/ml [range 832-1501]; t1: 1284 ng/ml [range 365-1501]; t2: 1240 ng/ml [range 263-1501]; P = 0.016) decreased significantly. Twelve cats underwent diagnostic imaging of the pituitary area. The median pituitary height at t0 of cats that experienced an IGF-1 reduction (n = 5/12) was significantly lower compared with those that did not experience an IGF-1 reduction (n = 7/12) (3.2 mm [range 3.1-3.7] vs 6 mm [range 3.5-9.5]; P = 0.011). Median fructosamine (t0: 628 µmol/l [range 400-963]; t1: 404 µmol/l [range 249-780]; t2: 400 µmol/l [range 260-815]; P <0.0001), insulin dose (t0: 1.3 IU/kg [range 0.5-4.6]; t0: 0.5 IU/kg [range 0-2.3]; t2: 0.4 IU/kg [range 0-2.1]; P <0.0001) and IRI (t0: 800 µmolIU/kgl [range 257-2700]; t1: 300 µmolIU/kgl [range 0-1498]; t2: 250 µmolIU/kgl [range 0-1498]; P <0.0001) decreased significantly during cabergoline treatment. Eight cats achieved diabetic remission between months 1 and 6 of cabergoline treatment (median time to achieve remission: 3 months [range 1-6]). Three cats experienced asymptomatic hypoglycemia.

CONCLUSIONS AND RELEVANCE

Cabergoline was effective in normalizing IGF-1 concentration in 26% of cats. Cabergoline improved diabetes control and was associated with remission of DM in 35% of cases. Cabergoline could be a treatment option for cats with HST and DM, especially in those cases with a relatively small pituitary tumor.

Quality of life and response to treatment in cats with hypersomatotropism: the owners' point of view

OBJECTIVES

The aim of this study was to collect clinical information from owners of cats with hypersomatotropism (HS) distributed worldwide, assessing the impact of HS and its treatments on cats' quality of life (QoL) and survival time.

METHODS

A survey focused on clinical presentation, diagnostic procedures, treatments, cats' QoL and disease progression was distributed worldwide to owners of cats with HS. The owner's perception of the cats' QoL before and after or during treatment was defined using a score ranging from 1 (poor) to 5 (excellent). Improvement following treatment (IFT) was quantified using a score ranging from 1 (absent) to 5 (obvious). Different treatment groups, including at least five cases, were compared.

RESULTS

A total of 127 cats were included from at least 11 different countries. Among these, 120 (95%) were diabetic and 7 (5%) were not. Out of 120 diabetic cats, 55 (46%) were treated with insulin as a single treatment (INS). Other treatments were not mentioned to owners in 35/120 (29%) cases. The median QoL score at diagnosis was 2 (range 1-5) and improved after treatment in all groups. Cabergoline (4; range 1-5), radiotherapy (4; range 2-5) and hypophysectomy (5; range 4-5) showed better median IFT scores compared with INS (3; range 1-5) (P = 0.046, P <0.002 and P <0.0001, respectively). Hypophysectomy IFT proved superior to cabergoline (P = 0.047) and was equal to radiotherapy IFT (P = 0.32). No difference was found between cabergoline and radiotherapy IFT (P = 0.99). The median survival time (MST) was 24 months (range 0-75 months). Cats treated with INS showed shorter MST (22 months; range 0-69 months) compared with cats treated with causal treatments combined (36 months; range 3-75 months) (P = 0.04).

CONCLUSIONS AND RELEVANCE

Not all cats with HS will have diabetes mellitus. Causal treatments seem associated with the greatest improvements in perceived cats' QoL and survival; such treatments should therefore be discussed with owners. Cabergoline could be an effective alternative management option.

Endocrine response and outcome in 14 cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (17 Gy)

OBJECTIVE

To describe clinical outcomes in cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (SRS).

ANIMALS

14 client-owned cats.

PROCEDURES

Medical records of cats with insulin resistance and acromegaly treated with SRS (17 Gy) between August 2013 and November 2019 at a single institution were reviewed. Kaplan-Meier analysis was used to evaluate overall survival time.

RESULTS

Acute adverse effects of SRS included somnolence (n = 2) and alopecia (1). Delayed adverse effects of SRS included unspecified neurologic complications (n = 1; 481 days), seizures (1; 1,541 days), and hypothyroidism (1; 64 days). Exogenous insulin requirements decreased in 10 of the 14 cats, with a median time to lowest insulin dose of 399 days (range, 42 to 879 days). Complete diabetic remission was achieved in 3 cats. The median overall survival time was 741 days (95% CI, 353 to 1,129 days). Six cats were still alive at the end of the study period, with a median follow-up time of 725 days. In 7 of the 8 cats that had died, death was presumptively attributed to acromegaly owing to continued insulin resistance, organ failure, or altered neurologic status.

CLINICAL RELEVANCE

The SRS protocol was well tolerated and associated with survival times similar to those reported previously. Most cats had decreased exogenous insulin requirements after SRS. Latency to an endocrine response was highly variable, emphasizing the need for careful ongoing diabetic monitoring of acromegalic cats after pituitary gland irradiation.

Diabetes mellitus remission in three cats with hypersomatotropism after cabergoline treatment

Case summary

Three diabetic cats presented with polyuria, polydipsia, polyphagia and poor glycemic control. Cat 1 displayed prognathia inferior and had a body condition score (BCS) of 4/5; cat 2 had a BCS of 5/5; and cat 3 had broad facial features. Serum insulin-like growth factor 1 concentrations were compatible with hypersomatotropism in cat 1 and cat 2 (>1500 ng/ml and 1200 ng/ml, respectively) and just below the cut-off of 1000 ng/ml (947 ng/ml) in cat 3; in this last cat diagnosis was further supported by the presence of pituitary enlargement on MRI. Oral cabergoline (10 μg/kg q48h) was initiated. Insulin requirements progressively reduced, as evidenced by daily blood glucose monitoring and weekly blood glucose curves. Diabetic remission occurred in all three cats between the second and third months of cabergoline treatment. At the time of writing, remission has persisted thus far (cat 1: 23 months; cat 2: 14 months; cat 3: 38 months).

Relevance and novel information

To our knowledge, these are the first reported cases of diabetic remission in cats with hypersomatotropism after cabergoline treatment, despite previous reports of this being an ineffective treatment. Further work is indicated to determine why some cats do, and others do not, respond to this treatment.

Acromegaly in dogs and cats

Acromegaly is an endocrine disease that leads to elevated production and secretion of growth hormone (GH). It can occur in adult and aged cats and is usually associated with neoplasms, such as functional pituitary macroadenoma of somatotropic cells. In dogs it is usually related to an increase in serum progesterone that induces production of GH by the mammary glands. The main clinical signs are related to insulin resistance and the anabolic effect induced by GH: polyuria, polydipsia, polyphagia, increased tissue growth, weight gain, prognathism, and other changes. The condition can be diagnosed from clinical signals and imaging associated to measurement of serum concentrations of GH and insulin-like growth factor 1 (IGF-1, also known as somatomedin C). The main therapeutic modalities are radiotherapy, hypophysectomy, and several drugs such as somatostatin analogs, dopaminergic agonists and GH receptor antagonists. The present review aims to provide a relevant animal model of acromegaly with an update on the therapeutic approach that may help clinicians to consider the GH axis-IGF-1 system, its pathogenesis and the clinical signs induced by this hormonal disorder.

Evaluation of hypophysectomy for treatment of hypersomatotropism in 25 cats

BACKGROUND

Successful treatment of cats with hypersomatotropism by transsphenoidal hypophysectomy is described in small numbers of cats.

OBJECTIVES

To describe the endocrine profile, survival, and remission rates of hypersomatotropism and diabetes mellitus in a cohort of cats with hypersomatotropism that underwent hypophysectomy between 2008 and 2020.

ANIMALS

Twenty-five client-owned cats with spontaneous hypersomatotropism.

METHODS

Retrospective study. Diagnosis of hypersomatotropism was based on clinical signs, plasma insulin-like growth factor-1 (IGF-1) concentration, and imaging of the pituitary gland. Growth hormone (GH) and IGF-1 concentrations were measured repeatedly after surgery. Survival times were calculated based on follow-up information from owners and referring veterinarians.

RESULTS

Median postoperative hospital stay was 7 days (range, 3-18 days). One cat died within 4 weeks of surgery. Median plasma GH concentration decreased significantly from 51.0 ng/mL (range, 5.0-101.0 ng/mL) before surgery to 3.8 ng/mL (range, 0.6-13.0 ng/mL) at 5 hours after surgery. Remission of hypersomatotropism, defined as normalization of plasma IGF-1 concentration, occurred in 23/24 cats (median, 34 ng/mL; range, 14-240 ng/mL) and 22/24 cats entered diabetic remission. Median survival time was 1347 days (95% confidence interval, 900-1794 days; range, 11-3180 days) and the overall 1-, 2-, and 3-year all-cause survival rates were 76%, 76%, and 52%, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study shows the beneficial outcome of hypophysectomy in cats with hypersomatotropism, marked by low death rate and a high percentage of diabetic remission and definitive cure.

Feline Pituitary Adenomas: Correlation of Histologic and Immunohistochemical Characteristics With Clinical Findings and Case Outcome

Pituitary glands from 141 feline autopsy cases were reviewed histologically. Adenoma and hyperplasia were the most common lesions at 13 cases each. Pituitary adenoma was more likely than hyperplasia to be associated with clinical evidence of endocrinopathy or an intracranial mass (P < .001). A histochemical and immunohistochemical panel was applied to 44 autopsy- or hypophysectomy-derived pituitary adenomas in 43 cats from 2 diagnostic laboratories. Adenomas were differentiated from hyperplasia by the presence of disrupted reticulin fibers. One cat had a double (somatotroph and melanotroph) adenoma. Twenty somatotroph adenomas consisted of periodic acid-Schiff (PAS)-negative acidophils that expressed growth hormone; 16/20 had hypersomatotropism; 17/20 had diabetes mellitus. Eleven melanotroph adenomas consisted of PAS-positive basophils or chromophobes that expressed melanocyte-stimulating and adrenocorticotrophic hormones; 5/11 had hypercortisolism; 6/11 had diabetes mellitus. Eleven gonadotroph adenomas consisted of PAS-negative chromophobes that expressed follicle-stimulating and/or luteinizing hormones. Two thyrotroph adenomas consisted of PAS-negative basophils or chromophobes that expressed thyroid-stimulating hormone. Pituitary-dependent disease was not recognized in cats with gonadotroph or thyrotroph adenomas. The Ki-67 proliferation index in hypophysectomy specimens was lower in somatotroph than in melanotroph adenomas. Fourteen cats with hypophysectomy-treated somatotroph or melanotroph adenoma had an 899-day median survival time versus 173 days in 17 nonsurgical cases. After adjusting for age, adenoma size and type, hypophysectomized cats had an overall better survival time than nonsurgical cases (P = .029). The study results underscore the value of hypophysectomy and trophic hormone immunohistochemistry in the treatment and classification of feline pituitary adenomas.

Efficacy of hypophysectomy for the treatment of hypersomatotropism-induced diabetes mellitus in 68 cats

Background

Hypersomatotropism (HST) is an increasingly recognized endocrinopathy in cats and is mostly described associated with diabetes mellitus (DM).

Objectives

To evaluate the efficacy and safety of transsphenoidal hypophysectomy in treating HST and DM in cats.

Animals

Sixty‐eight client‐owned cats with HST and DM treated by transsphenoidal hypophysectomy.

Methods

Retrospective cohort study. Medical records were reviewed for glycemic control and serum insulin‐like growth factor‐1 (IGF‐1) concentrations. Postoperative complications, death within 4 weeks, and proportion achieving diabetic remission were recorded. Survival times and DM‐free intervals were calculated.

Results

Fifty‐eight cats (85.3%) were alive 4 weeks postoperatively with 10 (15%) postoperative deaths. Complications included hypoglycemia (n = 9), electrolyte imbalance (n = 9), and transient congestive heart failure (n = 5). Fifty‐five cats (95% of 58 surviving cats [81% of all cats undergoing surgery]) had improved control of diabetes. Diabetic remission occurred in 41 cats (71% of 58 surviving cats [60% of all cats]) with insulin administration discontinued after a median of 9 days (range, 2‐120). Postoperative 4‐week serum IGF‐1 concentration nadir was significantly lower in cats achieving diabetic remission (median 20 ng/mL [15‐708] than those that did not (324 ng/mL [15‐1955]; P = .03). All cats received long‐term levothyroxine and hydrocortisone PO, alongside desmopressin (conjunctival) in 38 of 53 cats (72%). Recurrence of DM occurred in 5 of 41 cats (12%) after a median of 248 days (range, 84‐1232). Median survival time of all cats was 853 days (range, 1‐1740).

Conclusions and Clinical Importance

Transsphenoidal hypophysectomy is an effective treatment for cats with HST and DM, with a long‐term outcome that compares favorably to existing options.

Pilot study assessing the use of cabergoline for the treatment of cats with hypersomatotropism and diabetes mellitus

OBJECTIVES

An affordable and effective treatment is needed to manage feline hypersomatotropism. The aim of this study was to assess whether treatment with oral cabergoline for 90 days in cats with hypersomatotropism and diabetes mellitus improved diabetic and insulin-like growth factor 1 (IGF-1) control.

METHODS

This was a prospective cohort non-blinded pilot study enrolling client-owned cats with spontaneously occurring diabetes mellitus and hypersomatotropism. Cats received oral cabergoline (5-10 µg/kg q24h) for 90 consecutive days. Serum IGF-1 and fructosamine concentrations were measured on days 1, 30 and 90. Quality of life was determined using the DIAQoL-pet questionnaire on days 1 and 90.

RESULTS

Nine cats were enrolled and eight completed the study. There was no significant change in the following: IGF-1 (day 1 median 2001 ng/ml [range 890-2001 ng/ml]; day 30 median 2001 ng/ml [range 929-2001 ng/ml]; day 90 median 1828 ng/ml [range 1035-2001 ng/ml]; χ2(2) = 0.667, P = 0.805); fructosamine (day 1 median 499 µmol/l [range 330-887 µmol/l], day 30 median 551 µmol/l [range 288-722 µmol/l], day 90 median 503 [range 315-851 µmol/l]; χ2(2) = 0.581, P = 0.764); or DIAQoL-pet score (median on day 1 -2.79 [range -4.62 to -0.28], median on day 90 -3.24 [range -4.41 to -0.28]; P = 0.715). There was a significant change of insulin dose (χ2(2) = 8.667, P = 0.008) with cats receiving higher insulin doses at day 90 compared with day 1 (median on day 1 was 0.98 [range 0.63-1.49] and median on day 90 was 1.56 [range 0.49-2.55] units/kg q12h; P = 0.026).

CONCLUSIONS AND RELEVANCE

Cabergoline did not improve diabetic control or normalise insulin-like growth factor concentration, or improve patient quality of life.

Pituitary tumour types in dogs and cats

Pituitary tumours are common in dogs and are being increasingly recognized in cats. Pituitary tumours are usually classified as adenomas and should only be classified as carcinomas when there is evidence of metastatic spread of the tumour, which is rare. Despite the benign nature of most pituitary tumours, they can still compress or invade neighbouring tissues. Pituitary tumours can be functional (hormonally active) or non-functional (hormonally silent). The aim of this review was to provide an overview of the different pituitary tumour types in dogs and cats that have been reported in the literature. In dogs, the most common pituitary tumour type is the corticotroph adenoma, which can cause pituitary-dependent hypercortisolism. In cats, the most common pituitary tumour is the somatotroph adenoma, which can cause hypersomatotropism, and the second-most common is the corticotroph adenoma. A lactotroph adenoma has been described in one dog, while gonadotroph, thyrotroph and null cell adenomas have not been described in dogs or cats. Hormonally silent adenomas are likely underdiagnosed because they do not result in an endocrine syndrome. Tools used to classify pituitary tumours in humans, particularly immunohistochemistry for lineage-specific transcription factors, are likely to be useful to classify canine and feline pituitary tumours of unknown origin. Future studies are required to better understand the full range of pituitary adenoma pathology in dogs and cats and to determine whether certain adenoma subtypes behave more aggressively than others. Currently, the mechanisms that underlie pituitary tumorigenesis in dogs and cats are still largely unknown. A better understanding of the molecular background of these tumours could help to identify improved pituitary-targeted therapeutics.

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.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Updates in Feline Diabetes Mellitus and Hypersomatotropism

Flash glucose monitoring is a novel, noninvasive monitoring technique that is increasingly used in the management of small animal diabetes. This article provides guidance on the use of flash glucose monitoring in cats and demonstrates how this technique can be used in a range of feline diabetic cases, including those where management is proving challenging. Other aspects of complicated feline diabetic care are also discussed, including management of the sick diabetic cat, potassium depletion myopathy, and treatment options for cats with hypersomatotropism-associated diabetes mellitus. The use of insulin glargine 300 U/ml as a promising new long-acting insulin for diabetic cats is also discussed.

Effect of insulin treatment on circulating insulin-like growth factor I and IGF-binding proteins in cats with diabetes mellitus

BACKGROUND

Insulin-like growth factor-I (IGF-I) is used to screen for acromegaly in diabetic cats. In humans, most circulating IGF-I forms ternary complexes (TC) with IGF-binding protein (IGFBP-3) and an acid-labile subunit. Compared to humans, the amount of TC in cats is more variable. Insulin-like growth factor-I concentrations are reported to increase during insulin treatment, more rapidly in cats achieving remission.

OBJECTIVES

To investigate (i) factors associated with circulating IGF-I concentrations, including IGFBP-profiles (ii) effect of insulin treatment on IGF-I concentrations and (iii) IGF-I as prognostic marker of diabetes mellitus remission.

ANIMALS

Thirty-one privately owned diabetic cats of which 24 were followed 1 year, and 13 healthy cats.

METHODS

Prospective study. Serum insulin, IGF-I, glucose, and fructosamine concentrations were measured. IGF-binding forms were determined by chromatography in 14 diabetic and 13 healthy cats; and IGF-I, IGF-II, IGFBP-3, and IGFBP-5 by mass spectrometry in 3 cats achieving remission.

RESULTS

Insulin-like growth factor-I median (interquartile range) before start of insulin treatment was 300 (160-556) ng/mL. Insulin-like growth factor-I was positively associated with TC (P < .0001) and endogenous insulin (P = .005) and negatively associated with fructosamine (P < .0001). Median IGF-I was higher 2-4 weeks after start of insulin treatment compared with baseline (300 versus 670 ng/mL, P = .0001) and predicted future remission (P = .046). In cats that went into remission, the amount of TC and IGFBP-3 increased, suggesting increase in IGF-I is dependent on TC formation.

CONCLUSIONS

Insulin treatment should be accounted for when interpreting IGF-I in diabetic cats. Insulin-like growth factor-I 2-4 weeks after initiation of insulin treatment shows promise as prognostic marker for remission in diabetic cats.

Stereotactic radiation therapy for the treatment of functional pituitary adenomas associated with feline acromegaly

Background

Conventional fractionated radiotherapy has been shown to be partially effective for management of pituitary tumors in cats that cause acromegaly and diabetes mellitus (DM), but, the efficacy and safety of stereotactic radiation therapy (SRT) as a treatment for acromegalic cats has not been described.

Hypothesis

Stereotactic radiation therapy is an effective and safe treatment for controlling acromegaly associated with pituitary adenomas in cats. Additionally, SRT‐treated acromegalic cats with DM will experience a decrease in insulin requirements after radiation therapy.

Animals

Fifty‐three client‐owned cats referred to Colorado State University for SRT to treat pituitary tumors causing poorly controlled DM secondary to acromegaly.

Methods

Retrospective study of cats treated for acromegaly with SRT between 2008 and 2016 at Colorado State University. Diagnosis of acromegaly was based on history, physical examination, laboratory results, and cross‐sectional imaging of the pituitary. Signalment, radiation protocol, insulin requirements over time, adverse effects, and survival were recorded.

Results

Median survival time was 1072 days. Of the 41 cats for which insulin dosage information was available, 95% (39/41) experienced a decrease in required insulin dose, with 32% (13/41) achieving diabetic remission. Remission was permanent in 62% (8/13) and temporary in 38% (5/13) cats. Median duration to lowest insulin dose was 9.5 months. Of the treated cats, 14% developed hypothyroidism and required supplementation after SRT.

Conclusions

Stereotactic radiation therapy is safe and effective for treating cats with acromegaly. Cats treated with SRT have improved survival time and control of their DM when compared to previously reported patients treated with non‐SRT.

Diabetes mellitus remission in a cat with pituitary-dependent hyperadrenocorticism after trilostane treatment

Case summary

An 8-year-old male neutered Persian cat was presented with polyuria, polydipsia, polyphagia and muscle weakness associated with a 7 month history of diabetes mellitus (DM). The cat had initially been treated with neutral protamine Hagedorn (NPH) insulin 2 U q12h, followed by porcine lente insulin 2 U q12h and, most recently, 3 U glargine insulin q12h, without improvement of clinical signs. The cat also suffered from concurrent symmetrical bilateral alopecia of thorax and forelimbs, abdominal distension and lethargy. Hyperadrenocorticism (HAC), specifically pituitary-dependent HAC, was suspected and confirmed through abdominal ultrasonography demonstrating bilateral adrenal enlargement, and a low-dose dexamethasone suppression test using 0.1 mg/kg dexamethasone intravenously. Trilostane treatment (initially 10 mg/cat PO q24h then increased to 10 mg/cat PO q12h) was started and insulin sensitivity gradually improved, ultimately leading to diabetic remission after an increased in trilostane dose to 13mg/cat PO q12h, 14 months after the DM diagnosis and 7 months after the initiation of trilostane therapy.

Relevance and novel information

DM in cats with HAC is a difficult combination of diseases to treat. To our knowledge this is the first reported case of diabetic remission in a feline patient with HAC as a result of treatment with trilostane. Further work should focus on whether fine-tuning of trilostane-treatment protocols in cats with concurrent DM and HAC could lead to a higher proportion of diabetic remissions in this patient group.

Time spent with cats is never wasted: Lessons learned from feline acromegalic cardiomyopathy, a naturally occurring animal model of the human disease

BACKGROUND

In humans, acromegaly due to a pituitary somatotrophic adenoma is a recognized cause of increased left ventricular (LV) mass. Acromegalic cardiomyopathy is incompletely understood, and represents a major cause of morbidity and mortality. We describe the clinical, echocardiographic and histopathologic features of naturally occurring feline acromegalic cardiomyopathy, an emerging disease among domestic cats.

METHODS

Cats with confirmed hypersomatotropism (IGF-1>1000ng/ml and pituitary mass; n = 67) were prospectively recruited, as were two control groups: diabetics (IGF-1<800ng/ml; n = 24) and healthy cats without known endocrinopathy or cardiovascular disease (n = 16). Echocardiography was performed in all cases, including after hypersomatotropism treatment where applicable. Additionally, tissue samples from deceased cats with hypersomatotropism, hypertrophic cardiomyopathy and age-matched controls (n = 21 each) were collected and systematically histopathologically reviewed and compared.

RESULTS

By echocardiography, cats with hypersomatotropism had a greater maximum LV wall thickness (6.5mm, 4.1-10.1mm) than diabetic (5.9mm, 4.2-9.1mm; Mann Whitney, p<0.001) or control cats (5.2mm, 4.1-6.5mm; Mann Whitney, p<0.001). Left atrial diameter was also greater in cats with hypersomatotropism (16.6mm, 13.0-29.5mm) than in diabetic (15.4mm, 11.2-20.3mm; Mann Whitney, p<0.001) and control cats (14.0mm, 12.6-17.4mm; Mann Whitney, p<0.001). After hypophysectomy and normalization of IGF-1 concentration (n = 20), echocardiographic changes proved mostly reversible. As in humans, histopathology of the feline acromegalic heart was dominated by myocyte hypertrophy with interstitial fibrosis and minimal myofiber disarray.

CONCLUSIONS

These results demonstrate cats could be considered a naturally occurring model of acromegalic cardiomyopathy, and as such help elucidate mechanisms driving cardiovascular remodeling in this disease.

Time spent with cats is never wasted: Lessons learned from feline acromegalic cardiomyopathy, a naturally occurring animal model of the human disease

Background

In humans, acromegaly due to a pituitary somatotrophic adenoma is a recognized cause of increased left ventricular (LV) mass. Acromegalic cardiomyopathy is incompletely understood, and represents a major cause of morbidity and mortality. We describe the clinical, echocardiographic and histopathologic features of naturally occurring feline acromegalic cardiomyopathy, an emerging disease among domestic cats.

Methods

Cats with confirmed hypersomatotropism (IGF-1>1000ng/ml and pituitary mass; n = 67) were prospectively recruited, as were two control groups: diabetics (IGF-1<800ng/ml; n = 24) and healthy cats without known endocrinopathy or cardiovascular disease (n = 16). Echocardiography was performed in all cases, including after hypersomatotropism treatment where applicable. Additionally, tissue samples from deceased cats with hypersomatotropism, hypertrophic cardiomyopathy and age-matched controls (n = 21 each) were collected and systematically histopathologically reviewed and compared.

Results

By echocardiography, cats with hypersomatotropism had a greater maximum LV wall thickness (6.5mm, 4.1–10.1mm) than diabetic (5.9mm, 4.2–9.1mm; Mann Whitney, p<0.001) or control cats (5.2mm, 4.1–6.5mm; Mann Whitney, p<0.001). Left atrial diameter was also greater in cats with hypersomatotropism (16.6mm, 13.0–29.5mm) than in diabetic (15.4mm, 11.2–20.3mm; Mann Whitney, p<0.001) and control cats (14.0mm, 12.6–17.4mm; Mann Whitney, p<0.001). After hypophysectomy and normalization of IGF-1 concentration (n = 20), echocardiographic changes proved mostly reversible. As in humans, histopathology of the feline acromegalic heart was dominated by myocyte hypertrophy with interstitial fibrosis and minimal myofiber disarray.

Conclusions

These results demonstrate cats could be considered a naturally occurring model of acromegalic cardiomyopathy, and as such help elucidate mechanisms driving cardiovascular remodeling in this disease.

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.