Feline Acromegaly

Echocardiographic, morphometric and biomarker changes in female cats followed from 6 to 24 months of life

OBJECTIVES

The aim of the study was to evaluate cardiac size and early growth through echocardiographic, body weight (BW), body condition score (BCS), morphometric and biomarker changes in cats followed from 6 to 24 months of age.

METHODS

Twenty-four female European shorthair colony cats were evaluated at birth for BW and at 6, 12, 18 and 24 months of age for BW, BCS, head length (HL) and head width (HW), N-terminal pro B-type natriuretic peptide (NT-proBNP), insulin-like growth factor-1 (IGF-1) and echocardiographic measurements.

RESULTS

BCS, HW, left ventricular free wall in diastole, left atrium diameter and aortic diameter increased significantly between 6 and 12 months, while BW, HL and interventricular septum in diastole increased significantly between 6, 12 and 18 months, and BW decreased significantly between 18 and 24 months. NT-proBNP decreased significantly between 6 and 12 months. IGF-1 increased significantly between 6 and 12 months but decreased significantly between 12 and 18 months.

CONCLUSIONS AND RELEVANCE

This study prospectively evaluated changes in echocardiographic measurements, BW, BCS, HL, HW, IGF-1 and NT-proBNP in cats during the first 2 years of life. Results show a comparable change over time for different variables. These findings contribute to the understanding of a possible relationship between cardiac measures and body size from young age through to adulthood.

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.

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.

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.

Sciatic neuropathy in an acromegalic cat without concurrent diabetes mellitus

Case summary

A 17-year-old neutered male European Shorthair cat was presented owing to an inability to jump and respiratory stridor. The owner did not report any other clinical signs. On physical examination, the main findings were plantigrade stance, broad facial features and inspiratory stridor. Neurological examination revealed posterior paraparesis, hypotonia and right hindlimb muscle atrophy. Laboratory findings were unremarkable and glycaemia was normal. Serum insulin-like growth factor 1 concentration was elevated (>1000 ng/ml). A total body CT scan showed an enlarged pituitary gland, thickening of the nasal turbinates and an L7-S1 right foraminal stenosis. Electrodiagnostic testing confirmed the presence of a neuropathy affecting both sciatic nerves. The cat was treated with gabapentin only and was still alive and euglycaemic 16 months after the diagnosis.

Relevance and novel information

This case describes for the first time sciatic neuropathy, an occasional complication of acromegaly in people, as a possible clinical presentation in acromegalic cats without concurrent diabetes mellitus.

Acromegaly and ultrasound: how, when and why?

BACKGROUND

Acromegaly is a rare disease caused by an excess of growth hormone and insulin-like growth factor 1. It is usually diagnosed because of typical signs such as macroglossia, acral enlargement, jaw prognathism and malocclusion. Systemic complications are a major cause of morbidity and mortality in acromegaly, and many patients remain undiagnosed for several years. Increased ultrasound (US) application in the general population, and including among acromegaly patients, has revealed many suggestive features which, taken together with clinical suspicion, could induce suspicion of this disease.

PURPOSE

This review describes main US features in acromegaly. Echocardiography shows a typical cardiomyopathy, characterized by left ventricular hypertrophy, diastolic and systolic dysfunction, aortic and mitral regurgitation, and increased aortic root diameters. US preclinical markers of atherosclerosis, such as intima media thickness (IMT), seem also to be impaired. Visceromegaly and increased organ stiffness are other features of acromegaly, including enlarged prostate, kidneys, liver, and thyroid. In addition, other US findings are: renal cysts, micronephrolithiasis, impairment of renal haemodynamic parameters, gallstones and gallbladder polyps, hepatic steatosis, thyroid nodules, multinodular goiter, and polycystic ovaries. Musculoskeletal US findings are increased cartilage thickness, impaired density and elasticity of bones, nerve enlargement, carpal and cubital tunnel syndrome, and trigger finger.

CONCLUSIONS

Acromegaly patients frequently present systemic complications and a diagnostic delay. US features of acromegaly are not specific, but could potentially have a key role in early detection of the disease in the presence of typical clinical features.

Associations among echocardiography, cardiac biomarkers, insulin metabolism, morphology, and inflammation in cats with asymptomatic hypertrophic cardiomyopathy

Background

Insulin, insulin‐like growth factor‐1 (IGF‐1), and inflammation possibly are involved in cats with asymptomatic hypertrophic cardiomyopathy (aHCM).

Objectives

To evaluate echocardiography, morphology, cardiac and inflammatory markers, insulin and IGF‐1 in cats with aHCM.

Animals

Fifty‐one client‐owned cats with aHCM.

Methods

Observational descriptive study. Variables (body weight [BW], body condition score [BCS], echocardiography, and serum concentrations of N‐terminal pro‐B‐type natriuretic peptide [NT‐proBNP], ultra‐sensitive troponin‐I [c‐TnI], serum amyloid A [SAA], insulin, glucose and IGF‐1) were evaluated for significant increases above echocardiography cutoff values and laboratory reference ranges, associations and effect of left atrial (LA) remodeling and generalized hypertrophy.

Results

Cats with aHCM had BCS ≥6/9 (P = .01) and insulin (P < .001), NT‐proBNP (P = .001) and cTn‐I (P < .001) above laboratory reference ranges. Associations were present between NT‐proBNP and maximum end‐diastolic interventricular septum thickness (IVSd; ρ = .32; P = .05), maximum end‐diastolic left ventricular free wall thickness;(ρ = .41; P = .01), LA/Aorta (ρ = .52; P = .001) and LA diameter (LA‐max; ρ = .32; P = .05); c‐TnI and LA/Aorta (ρ = .49; P = .003) and LA‐max (ρ = .28; P = .05); and SAA and number of IVSd regions ≥6 mm thickness (ρ = .28; P = .05). Body weight and BCS were associated with IGF‐1 (r = 0.44; P = .001), and insulin (ρ = .33; P = .02), glucose (ρ = .29; P = .04) and IGF‐1 (ρ = .32; P = .02), respectively. Concentrations of NT‐proBNP (P = .02) and c‐TnI (P = .01), and SAA (P = .02), were higher in cats with LA remodeling, and generalized hypertrophy, respectively.

Conclusions and clinical importance

Results suggest potential implications of insulin, IGF‐1, and inflammation in cats with aHCM, but it remains to be confirmed whether these findings represent a physiological process or a part of the pathogenesis and development of disease.

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.

Acromegaly in a non-diabetic cat

Case summary

A 14-year-old, neutered male European shorthair cat was evaluated for a routine health check. The owner did not report any clinical signs except for respiratory stridor. On physical examination the main findings were broad facial features and increased interdental spaces. On haematology, a mild, non-regenerative anaemia was detected, whereas the serum biochemistry profile and urinalysis were unremarkable. The serum glucose concentration was within the reference interval. Serum insulin-like growth factor-1 concentration was markedly elevated (>1600 ng/ml). The basal serum growth hormone concentration was elevated and decreased only mildly after somatostatin administration. Basal serum insulin concentration was high, and the insulin concentration increased considerably after glucose loading, consistent with insulin resistance. CT scanning of the skull showed an enlarged pituitary gland and increased skull bone thickness. The final diagnosis was acromegaly.

Relevance and novel information

These findings demonstrate that acromegaly should be pursued and suspected in cats other than those with diabetes mellitus.

Serum N-Terminal Type III Procollagen Propeptide: An Indicator of Growth Hormone Excess and Response to Treatment in Feline Hypersomatotropism

Background

N‐terminal type III procollagen propeptide (PIIINP) is a biomarker of soft tissue proliferation. Hypersomatotropism (HS) is associated with soft tissue proliferation.

Hypothesis

Serum PIIINP is increased in cats with HS and decreases with effective treatment, and may be an additional tool in the diagnosis and treatment of feline HS.

Animals

Cats with uncomplicated diabetes mellitus (DM; n = 30) and with HS‐induced DM (HSDM; n = 30). Pre‐ and posttreatment samples were available from 5 cats undergoing radiotherapy (RT) and 16 cats undergoing hypophysectomy (HPX).

Methods

Retrospective and prospective cross‐sectional study. Analytical performance of a serum PIIINP ELISA was assessed and validated for use in cats. PIIINP and insulin‐like growth factor 1 (IGF‐1) radioimmunoassays (RIA) were performed pre‐ and post‐treatment in cats with DM and HSDM. PIIINP and IGF‐1 were compared between cats treated by RT and HPX.

Results

Serum PIIINP concentrations were significantly higher (P < .001) in HSDM cats (median, 19.6 ng/mL; range, 1.7–27.9) compared to DM cats (median, 5.0 ng/mL; range, 2.1–10.4). A cut‐off of 10.5 ng/mL allowed differentiation between DM and HSDM cats with 87% sensitivity and 100% specificity (area under the curve [AUC], 0.91; 95% confidence interval [CI], 0.82‐1). After RT, PIIINP increased significantly (P = .043) with no significant change in IGF‐1 concentrations. After HPX, serum PIIINP (P = .034) and IGF‐1 concentrations (P < .001) decreased significantly.

Conclusion and clinical importance

PIIINP concentrations are increased in cats with untreated HSDM compared to those with DM, demonstrating the effect of excess GH on soft tissue. PIIINP concentrations decreased after HPX in most HSDM cats.

Anatomopathological staging of feline hypertrophic cardiomyopathy through quantitative evaluation based on morphometric and histopathological data

Diagnosis of feline hypertrophic cardiomyopathy (HCM) is both clinical and anatomopathological. Since standardized echocardiographic parameters have previously been established for its diagnosis and classification, the aim of the present study is to provide an original, complete and repeatable quantitative anatomopathological evaluation of this myocardial disease. Since ES-HCM is a clearly defined clinicopathological entity of feline HCM, the present study also aims to investigate its temporal evolution. The hearts of 21 cats with previous diagnosis or suspicion of HCM and 6 control animals were submitted for morphometric and histopathological investigations. The proposed quantitative assessment of gross and histopathological features of HCM appears to be original and repeatable. Correlations between morphometric data allow to establish that the progression to the end-stage phenotypes, primarily characterized by increase in left ventricular fibrous tissue deposition, is accompanied by dilation of left ventricular lumen (P=0.0004) and left atrium (P=0.0017) and increase in intramural coronary arteriosclerosis (P=0.0293).

Echocardiographic findings in 11 cats with acromegaly

Background

Information regarding cardiac changes in domestic cats with acromegaly is limited.

Hypothesis/Objectives

The objective of this study was to describe the echocardiographic findings in cats with acromegaly.

Animals

Eighteen cats diagnosed with acromegaly at Colorado State University between 2008 and 2012. Of these 18 cats, 11 had echocardiography performed.

Methods

A retrospective review of medical records was made to identify cats with acromegaly that also had echocardiography performed.

Results

Of the 11 cats identified, 7 had left ventricular concentric hypertrophy, 6 had left atrial enlargement, and 7 had evidence of abnormal diastolic function. All 11 cats had evidence of structural or functional cardiac disease.

Conclusions and Clinical Importance

Cardiovascular abnormalities frequently are present in cats with acromegaly, and a complete cardiac evaluation should be considered in these patients.