Feline Endocrinology

Edward C. Feldman, DVM, DACVIM (Small Animal Internal Medicine), Emeritus Professor of Small Animal Internal Medicine, University of California, Davis, California, USA

Federico Fracassi, DVM, DECVIM-CA (Internal Medicine), Associate Professor of Small Animal Internal Medicine, Department of Veterinary Medical Sciences, University of Bologna, Italy

Mark E. Peterson, DVM, DACVIM (Small Animal Internal Medicine), Animal Endocrine Clinic, New York, NY, Adjunct Professor of Medicine, Department of Clinical Sciences Cornell University, College of Veterinary Medicine, Ithaca, NY, USA

SECTION 1 - HYPOTHALAMUS AND PITUITARY

Chapter 1 Pituitary anatomy and physiology
Pituitary anatomy
Pituitary physiology
Hormones of the adenohypophysis (AL)
Hormones of the neurohypophysis

Chapter 2 GH excess: acromegaly (hypersomatotropism)
Background and history
Incidence and pathogenesis
Pituitary pathology
Consequences of pituitary pathology
Clinical features and diagnosis
Treatment
Prognosis

Chapter 3 Other pituitary tumors
Pituitary masses: hyperplasia, adenoma or carcinoma?
Incidence and cell origins of pituitary tumors
Effect of pituitary tumors on target organs and the direct effects of large tumors
Functional consequences of autonomous hormone production

Chapter 4 Pituitary surgery
Introduction and general observations
Surgical anatomy
Imaging of the feline pituitary gland
Pituitary adenomas
Transsphenoidal hypophysectomy
Postoperative care
Complications after pituitary surgery
Prognosis

Chapter 5 Pituitary irradiation
Introduction
Clinical presentation
Advanced imaging
Role of radiation therapy
Modalities of radiation therapy
Nonfunctioning tumors
Growth hormone-secreting pituitary tumors and acromegaly
Adrenocorticotropic hormone-secreting pituitary tumors and feline Cushing’s disease
Radiation-related adverse effects

Chapter 6 Pituitary GH deficiency and pituitary dwarfism
Introduction
Etiopathogenesis
Clinical features
Differential diagnosis for failure to grow
Diagnosis
Treatment

Chapter 7 Polyuria, polydipsia and diabetes insipidus
Introduction
Water requirements in healthy cats
Urine concentrating ability in healthy cats
Mechanisms of water retention
Causes of polyuria and polydipsia in cats
The diagnostic approach to polyuria and polydipsia
Treatment of central diabetes insipidus
Prognosis

SECTION 2 - THYROID GLAND

Chapter 8 Thyroid anatomy and physiology
Anatomy of the feline thyroid gland
General thyroid physiology
Serum protein binding of thyroid hormones
Hypothalamic-pituitary-thyroid axis
Extrathyroidal metabolism of thyroid hormone
Thyroid hormone kinetics in the cat
Action of thyroid hormone

Chapter 9 Hyperthyroidism: background, etiopathogenesis and changing prevalence of feline thyroid disease
History of thyroid disease in cats
Studies into the etiopathology of feline hyperthyroidism
Epidemiology of hyperthyroidism: a common worldwide disorder of senior to geriatric cats
Why has feline nodular goiter reached such epidemic proportions?
Conclusions

Chapter 10 Hyperthyroidism: clinical signs and physical examination findings
Signalment
Clinical signs
Physical examination

Chapter 11 Hyperthyroidism: laboratory diagnosis
Clinicopathologic abnormalities associated with hyperthyroidism
Thyroid hormone abnormalities associated with hyperthyroidism
Other diagnostic tests
Conclusion

Chapter 12 Thyroid and kidney disease in cats
Hyperthyroidism and chronic kidney disease (CKD)
Effect of hyperthyroidism on serum test results of renal function
Effect of hyperthyroidism on urinary markers of renal function
Effect of hyperthyroidism on systolic blood pressure
Effect of treatment of hyperthyroidism on renal function
Effect of azotemia on how hyperthyroid cats are managed
Suggested management strategies for hyperthyroid cats with CKD

Chapter 13 Thyroid imaging
Introduction
Thyroid embryology, radiographic anatomy, and ectopic thyroid tissue
Normal thyroid
Hyperthyroidism
Ectopic thyroid
Thyroid carcinoma
Thyroid cysts
Hypothyroidism

Chapter 14 Treatment of hyperthyroidism: antithyroid drugs
Considerations prior to initiating therapy with antithyroid drugs
Mechanism of action of antithyroid drugs
Formulations of antithyroid drugs
Dosages of antithyroid drugs
Adverse reactions with antithyroid drugs
Monitoring cats treated with antithyroid drugs
Other drugs of interest in managing hyperthyroid cats
Success rate and survival in hyperthyroid cats managed with an antithyroid drug
Renal function and hyperthyroidism
Conclusion

Chapter 15 Treatment of hyperthyroidism: surgical thyroidectomy
Introduction and overview
Anatomy of the thyroid gland and surrounding structures
Preoperative evaluation
General anesthesia
Feline thyroidectomy techniques
Perioperative complications
Postoperative recurrence of hyperthyroidism
Surgical excision of thyroid adenocarcinoma
Summary and conclusions

Chapter 16 Treatment of hyperthyroidism: radioiodine
Introduction
Advantages and disadvantages of radioiodine treatment of hyperthyroidism
Principles of radioiodine treatment
Specific indications for radioiodine treatment
Patient selection and preparation before radioiodine treatment
Thyroid scintigraphy for evaluation of hyperthyroid cats before 131I treatment
Estimation of the radioiodine dose to administer to cats with hyperthyroidism
Adverse effects or complications associated with radioiodine treatment
Follow-up thyroid function testing after radioiodine treatment
Prognosis after radioiodine treatment

Chapter 17 Treatment of hyperthyroidism: diet
General nutritional assessment for the hyperthyroid cat
Weight loss and muscle wasting
Nutrients needed for the hyperthyroid cat
Nutritional management of feline hyperthyroidism: feeding alow-iodine diet

Chapter 18 Treatment of hyperthyroidism: severe, unresponsive, or recurrent hyperthyroidism
Introduction
Etiology and pathogenesis of severe, unresponsive or recurrent hyperthyroidism
Correlation between the severity and duration of hyperthyroidism and the severity of clinical signs
Causes for treatment failure
Therapy for severe, unresponsive hyperthyroidism
Summary

Chapter 19 Hypothyroidism
Introduction
Causes of hypothyroidism
Clinical subtypes of hypothyroidism
Naturally occurring, congenital hypothyroidism in kittens and junior cats
Naturally occurring hypothyroidism in adult cats
Iatrogenic hypothyroidism in adult cats
Refractory hypothyroidism

SECTION 3 - CALCIUM AND PARATHYROID GLANDS

Chapter 20 Hypercalcemia
Overview
Calcium physiology
Laboratory testing
Initial investigation in hypercalcemic cats
Differential diagnosis of hypercalcemia

Chapter 21 Feline primary hypoparathyroidism and hypocalcemia
Introduction
Distribution of calcium in the body
Control of calcium (Ca) homeostasis
Hypocalcemia in people and dogs
Hypoparathyroidism in cats
Differential diagnosis of hypocalcemia
Diagnostic testing
Treatment

SECTION 4 - ADRENAL GLANDS

Chapter 22 Adrenal anatomy and physiology
Adrenal anatomy
Adrenal physiology

Chapter 23 Cushing’s syndrome (hypercortisolism)
Introduction
Etiology
Clinical features
Clinicopathological findings
Endocrine testing
Diagnostic imaging
Treatment
Prognosis

Chapter 24 Primary hyperaldosteronism (Conn’s syndrome)
Introduction
Primary hyperaldosteronism

Chapter 25 Other adrenal cortical tumors and pheochromocytoma
Introduction and differential diagnosis
Working up a feline adrenal mass
Excessive progesterone production
Combined excesses in progesterone and aldosterone
Excessive androgen or estradiol production
Pheochromocytoma
Non-functional adrenal tumors

Chapter 26 Adrenal surgery via open and laparoscopic approaches
Introduction
Diagnostic evaluation
Case selection
Patient preparation
Surgical techniques
Post-operative care
Complications

Chapter 27 Feline hypoadrenocorticism
Introduction
Prevalence
Causes
Age, breed and gender
Clinical signs
Clinical pathology
Diagnostic imaging
Electrocardiography and echocardiography
Endocrine tests
Differential diagnoses
Treatment
Prognosis

Chapter 28 Glucocorticoid therapy
Physiology
Pharmacology
Therapeutic applications
Adverse effects
Glucocorticoid reduction protocol

SECTION 5 - ENDOCRINE PANCREAS

Chapter 29 Anatomy, histology and physiology of the feline endocrine pancreas
Anatomy of the feline pancreas
Cell types
Cross-differentiation
General function of islet hormones
Secretory control
Relative importance of pancreatic hormones and their contribution to the pathophysiology of diabetes mellitus
Pancreatic amyloid as the most typical histological finding in diabetes mellitus

Chapter 30 Pathogenesis and clinical observations of uncomplicated diabetes mellitus
Introduction
Prevalence and epidemiology
Risk factors
Pathophysiologic mechanisms
DM and pancreatitis
Clinical and laboratory findings
Survival and prognostic factors

Chapter 31 Diabetic ketosis, ketoacidosis, and the hyperosmolar syndrome
Introduction
Glucose homeostasis
Clinical presentation of DKA and HHS
Principles of management of DKA and HHS
Fluid and electrolyte therapy
Insulin therapy
Additional supportive therapy in DKA and HHS
Prognosis of DKA and HHS in cats

Chapter 32 Insulin treatment of diabetes mellitus
Aims of the treatment and management plan
Insulin therapy
Choosing an insulin
Frequency of insulin administration, initial insulin dose and change in the type of insulin
Storage, mixing and dilution of insulin
Owner education
Insulin dosing pens

Chapter 33 Gastrointestinal hormones and the use of non-insulin therapies for diabetes mellitus
Introduction
Incretin hormones physiology and pharmacology
Metformin
Glipizide
Acarbose
SGLT-2 antagonists
Challenges in managing feline DM and potential uses of non-insulin therapies

Chapter 34 Dietary management for diabetes mellitus
Overview
Learning outcomes
Case 1: feeding cats that refuse or dislike their “diabetes diet”
Case 2: an insulin overdosed diabetic cat that has just recovered from a severe “hypo” (neuroglycopenia)
Case 3: non-prescription diet alternatives
Case 4: achieving weight loss in a diabetic cat
Case 5: managing diabetes in a cat with concurrent disease
Case 6: the client has looked up a lot of information about diabetes in cats on the internet

Chapter 35 Monitoring diabetes in cats
Clinical signs
Blood glucose monitoring
Continuous glucose monitoring systems (CGMS) and flash glucose monitoring systems
Urine glucose measurement
Fructosamine concentration
Glycated hemoglobin

Chapter 36 Diabetic remission
Definition of diabetic remission
Physiology of diabetic remission
Incidence of diabetic remission
Predictors of diabetic remission
Maximizing the likelihood of diabetic remission
Identification and management of the diabetic cat in remission
Prognosis and diabetic relapse
Conclusions

Chapter 37 The unstable diabetic
Overview
Initial goals of therapy and factors that influence remission
Classification of diabetes mellitus and relevance to unstable diabetic cats
Inappropriate choice of insulin
Inappropriate dosing
Choice of intensive versus conservative insulin management of newly-diagnosed diabetics
Client factors
Underlying diseases
Rebound hypoglycemia (Somogyi)
The brittle diabetic
Monitoring
Other management strategies
Conclusion

Chapter 38 Hypoglycemia
Introduction
Pathophysiology of hypoglycemia
Blood glucose measurement
Differential diagnoses
Specific diseases or syndromes associated with hypoglycemia in cats
Diagnostic approach
Treatment of hypoglycemia

SECTION 6 - BLOOD PRESSURE, BODY CONDITION AND NUTRITION

Chapter 39 Feline obesity
Epidemiology
Pathophysiology of obesity
Obesity-related diseases
Treatment

Chapter 40 Disorders of lipid metabolism
Introduction
The basics of lipoprotein metabolism
Definitions and measurement of feline serum lipid concentrations
Effect of lipemia on the measurement of other analytes
Causes of feline hyperlipidemia
Clinical consequences of hyperlpidemia in cats
Diagnostic approach to cats with hyperlipidemia
Treatment of feline hyperlipidemia

Chapter 41 Cachexia and sarcopenia
Cachexia
Sarcopenia
Diagnosis of cachexia and sarcopenia
Potential interventions for cachexia and sarcopenia
Practical approach to treatment of cachexia and sarcopenia in cats
Conclusion

Chapter 42 Hypertension
Introduction
Measurement of blood pressure incats
Defining hypertension and deciding when to treat
Consequences of hypertension
Endocrine causes of hypertension
Management of hypertension
Annex Conversion tables
Conversion to Systeme International (SI) Units