The summary of all summaries

Pituitary Gland

Functions

• Metabolic regulation, chemical reaction rates, and membrane transport.

• Controls cellular metabolism, growth, and secretion.

Structure

• Cell Types:

  • Acidophils: Produce Growth Hormone (GH) and Prolactin.

  • Basophils: Produce Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH).

  • Chromophobes: Support cells.

Major Disorders

Adenohypophyseal Hyperfunction

• Cushing Disease (ACTH)

• Hyperthyroidism (TSH)

• Gigantism/Acromegaly (STH)

Adenohypophyseal Hypofunction

• Hypothyroidism (TSH)

• Dwarfism (STH)

• Reproductive Disorders (FSH/LH)

• Generalized Syndromes: Adiposo-genital syndrome, pituitary cachexia.

Developmental Disorders

Species-Specific Manifestations

• Cattle:

  • Genetic defects in Guernsey and Jersey breeds.

  • Target organ hypoplasia; prolonged gestation due to adrenal cortex issues.

• Sheep:

  • Caused by Veratrum californicum ingestion; results in cranial malformations and pituitary abnormalities.

• Dogs:

  • Affects German Shepherd, Spitz, Toy Pinscher breeds; characterized by pituitary cysts and dwarfism, symptoms include stunted growth and skin changes.

Neoplastic Conditions

• Functional Adenomas:

  • Corticotroph Adenomas – common in dogs, causes Cushing's disease and adrenal cortical hyperplasia.

  • Somatotroph Adenomas – causes acromegaly and diabetes mellitus, notable in cats leading to tissue overgrowth and metabolic changes.

  • Pars Intermedia Dysfunction (PPID) – significant in horses, symptoms include abnormal hair growth, metabolic disturbances, increased infection susceptibility, and chronic laminitis.

• Non-functional Tumors:

  • Chromophobe adenomas, craniopharyngiomas, and pituitary carcinomas leading to panhypopituitarism, diabetes insipidus, and neurological dysfunction.

Neurohypophyseal Disorders

Diabetes Insipidus

• Central Form: Reduced ADH secretion caused by various lesions.

• Nephrogenic Form: Kidney resistance to ADH; hereditary condition with symptoms of polyuria and polydipsia.

Inflammatory Conditions

• Pituitary abscesses.

• Bacterial and mycotic infections associated with neurological complications.

Adrenal Gland

Functions

• Metabolic regulation, chemical reaction rates, cellular metabolism, growth, and secretion.

• Endocrine glands are scattered, lack physical continuity, and release hormones into the bloodstream.

Adrenal Cortex Disorders

Hyperadrenocorticoidism (Cushing's Disease)

• Types and Occurrence:

  • Common in older dogs, less frequent in horses.

  • Primary (10-15%): Cortical neoplasm or idiopathic hyperplasia.

  • Secondary (80%): Bilateral cortical hyperplasia from pituitary tumor.

  • Pharmacological (5-10%): Excessive glucocorticoid administration.

  • Ectopic ACTH syndrome: Non-pituitary/adrenal tumors producing ACTH.

• Clinical Signs and Complications:

  • Metabolic effects like diabetes mellitus, obesity, osteoporosis; skin changes including atrophy, symmetric alopecia, calcinosis cutis; systemic effects such as polyuria, polydipsia, polyphagia, hepatomegaly; complications encompass cataracts, ulcers, hypertension, infections, and immunosuppression.

Neoplasia and Hyperplasia

Cortical Adenomas

• Common in older dogs, castrated male goats, neutered ferrets; well-demarcated, unilateral yellow to red nodules, usually functional and encapsulated.

Cortical Carcinomas

• Rare occurrence in cattle, dogs, ferrets; often bilateral with vena cava invasion; can lead to severe contralateral adrenal atrophy.

Hyperplasia Types

• Nodular: Common in older animals.

• Diffuse: Bilateral enlargement often from ACTH hypersecretion.

Hypoadrenocorticism (Addison's Disease)

Causes

• Primary: Bilateral idiopathic adrenal cortical atrophy.

• Secondary: ACTH deficiency from pituitary lesions.

• Various infections including viral, bacterial, fungal, parasitic, and other causes like trauma, severe stress, and tumors.

Clinical Signs

• Lethargy, stress intolerance, bradycardia; gastrointestinal issues include anorexia, vomiting, diarrhea; electrolyte imbalances such as hyperkalemia, hyponatremia; chronic signs like hyperpigmentation and reduced adrenal cortex thickness.

Special Conditions

• Functional Proliferative Lesions in Ferrets: Second most common neoplasm in adult ferrets, early spayed/neutered animals show signs like alopecia, polyuria/polydipsia, and anemia.

• Hyperaldosteronism in Cats: Common in aged cats, causing systemic hypertension and muscle weakness characterized by increased aldosterone and electrolyte imbalances.

Adrenal Medulla Disorders

Pheochromocytoma

• Most common medullary neoplasm; prevalent in dogs and cattle; can be extra-adrenal as paragangliomas; symptoms include tachycardia, hypertension, cardiac hypertrophy; diagnosed through chromaffin reaction; may be functional or non-functional.

Thyroid Gland

Functions

• Involved in metabolic regulation, chemical reactions, and controls substance transport through cell membranes; manages cellular metabolism, growth, and secretion.

Thyroid Gland Disorders

Hypothyroidism

• Clinical Signs:

  • Metabolic: obesity, hypercholesterolemia, atherosclerosis.

  • Dermatologic symptoms (SAD FACE): symmetric alopecia, hyperkeratosis, follicular keratosis, hyperpigmentation, myxedema.

  • Additional symptoms: lethargy, weight gain, muscular weakness, sexual inactivity, reproductive failures, joint pain, low T3 and T4 levels, normocytic normochromic anemia.

• Causes:

  • Congenital Dyshormonogenetic Goiter: Genetic thyroglobulin synthesis impairment; common in sheep, Afrikander cattle, Saanen goats.

  • Idiopathic Follicular Atrophy: Loss of follicular epithelium replaced by adipose tissue.

  • Lymphocytic Thyroiditis: Similar to human Hashimoto's disease, characterized by inflammatory cell infiltrates.

  • Congenital Hypothyroidism-Dysmaturity Syndrome: Affects horses in the Pacific Northwest related to maternal iodine deficiency.

Hyperthyroidism

• Clinical Signs:

  • Cervical swelling; respiratory issues; cardiac problems (especially in cats); calcium homeostasis disturbances; behavioral changes (nervousness, anxiety); heat intolerance.

• Causes:

  • Hyperplasia; neoplasms (adenomas, carcinomas); most common in aged cats.

Goiter

Types and Characteristics

• Diffuse Hyperplastic Goiter: Common in young animals, caused by iodine deficiency or excess, shows enlarged glands with irregular follicles.

• Colloid Goiter: Involutionary phase of hyperplastic goiter; large follicles with dense eosinophilic colloid occurs after iodine correction.

• Multifocal Nodular Hyperplasia: Common in older animals; functional in cats; associated with diet and environmental factors.

Thyroid Neoplasms

Follicular Cell Tumors

• Adenomas: Well-demarcated, encapsulated, more common in cats.

• Carcinomas: Common in dogs (especially beagles, boxers), early metastasis to lungs, can arise from accessory thyroids.

C Cell (Parafollicular) Tumors

• Produce calcitonin and regulate calcium homeostasis; types include C cell hyperplasia, adenoma, carcinoma; common in aged bulls and may occur with other neural crest tumors.

Parathyroid Gland

Functions

• Functions in metabolic regulation, chemical reaction rates, and membrane transport; controls cellular metabolism, growth, and secretion; glands are scattered with diverse embryological origins, releasing hormones directly into the bloodstream.

Parathyroid Function

Physiological Effects of Parathyroid Hormone

• Bone: Promotes calcium efflux through osteoclast activity.

• Kidney: Reduces calcium loss in urine and signals vitamin D production.

• Intestines: Enhances calcium absorption.

Major Disorders

Hypoparathyroidism

• Clinical Manifestations:

  • Hypocalcemic tetany, restlessness, nervousness, ataxia, weakness, muscle tremors, tetany, convulsive seizures, increased blood phosphorus levels.

• Causes:

  • Lymphocytic parathyroiditis, parturient paresis (milk fever), other causes like neoplasm destruction, surgical removal, and calcinogenic plant ingestion.

Hyperparathyroidism

• Primary Hyperparathyroidism: Causes include hyperplasia, adenomas, carcinomas; leads to fibrous osteodystrophy, hypercalcemia, bone weakening, fractures, muscular weakness.

• Secondary Hyperparathyroidism:

  • Nutritional Form: Affects species like dogs and cats on all-meat diets; caused by calcium-deficient diets or high phosphorus.

  • Renal Form: Common in dogs/cats caused by chronic renal failure leading to hypocalcemia, hyperphosphatemia, impaired vitamin D3 activation, increased PTH levels.

Pseudohyperparathyroidism

• Paraneoplastic syndrome with hypercalcemia and hypophosphatemia, often caused by PTH-related protein secretion from tumor cells; manifests in anal sac adenocarcinoma and lymphosarcoma.

Treatment Considerations

• Dietary management is crucial in nutritional forms; surgical intervention for tumors; calcium supplementation when needed; regular monitoring of calcium and phosphorus levels.

Pancreas, Islets, & Chemoreceptors

Functions

• In metabolic regulation, chemical reaction rates, and membrane transport; controls cellular metabolism, growth, and secretion.

Endocrine Glands

• Scattered throughout the body without physical continuity; diverse embryological origins; synthesize, store, and release hormones directly into the bloodstream; act as sensing and signaling devices in extracellular fluid.

Pancreatic Disorders

Diabetes Mellitus

• Type 1 (Juvenile-onset): Characterized by beta cell destruction, complete loss of insulin secretion, sudden onset requiring immediate insulin therapy. Causes include toxins, immune-mediated responses, viral infections, cytokines, free radical injury, islet abnormalities.

• Type 2 (Maturity-onset): Features insulin resistance/beta cell dysfunction, gradual loss of insulin secretion, variable insulin levels; initially controllable with small doses, may progress to insulin dependency.

• Secondary Diabetes: Caused by hormonal antagonism or sustained hyperglycemia.

Species-Specific Presentations

• Dogs: Common endocrinopathy, predominantly Type 1, more frequent in females; caused by islet destruction, pancreatic issues, or immune-mediated processes.

• Cats: Primarily Type 2 diabetes, associated with islet amyloidosis.

Clinical Signs and Complications

• Hyperglycemia, glycosuria, polydipsia/polyuria, increased appetite with weight loss, bilateral cataracts, weakness, hepatomegaly, recurrent infections, kidney, and vascular complications.

Pancreatic Neoplasia

Beta Cell Tumors (Insulinomas)

• More common in adult dogs, cattle, and ferrets; present as adenomas or carcinomas; causes hypoglycemia, clinical signs include weakness and seizures.

Non-Beta Cell Tumors

• Glucagonomas: Rare in dogs, causes secondary diabetes; associated with hepatocutaneous syndrome.

• Gastrinomas: Rare in dogs/cats; causes Zollinger-Ellison syndrome leading to GI ulcerations.

Equine Metabolic Syndrome

• Affects inactive horses, especially ponies; associated with high-energy diets; characterized by obesity, insulin resistance, and can lead to chronic laminitis.

Chemoreceptors

Structure and Function

• Located in body sites including carotid and aortic bodies; monitor blood CO2, pH, and oxygen; regulate respiration and circulation.

Neoplasms

• Aortic Body Tumors: Represent 80% of chemoreceptor tumors, present as heart-base masses and can cause heart failure.

• Carotid Body Tumors: Located near carotid artery bifurcation, usually unilateral, can interfere with swallowing and blood flow.

• Ectopic Thyroid Tumors: Represent 5-10% of heart-base tumors; compress mediastinal structures.

External Ear

Structure and Function

• Comprises skin-covered cartilaginous pinna and external ear canal with hairs and ceruminous glands.

Common Conditions

Congenital Anomalies

• Includes macrotia, microtia, anotia, polyotia, atresia, and persistent meatal plugs.

Auricular Hematomas

• Common in dogs, cats, pigs; characterized by firm, warm fluid swelling, can lead to deformity and fibrosis; caused by trauma.

Otitis Externa

• Most common ear disease, often mixed infections; symptoms include hair loss, thickening, pruritus, hyperplasia; can lead to chronic conditions and deafness due to multiple causes including parasites.

Middle Ear

Structure and Function

• Located within temporal bone, contains tympanic membrane and Eustachian tube, houses ear ossicles for sound conduction.

Pathological Conditions

Otitis Media

• Congestion and fluid exudation can lead to fibrous polyps and deafness; common bacterial causes include Truperella pyogenes and Pasteurella; can lead to guttural pouch empyema in horses.

Neurological Complications

• Horner's Syndrome: Affects sympathetic nerve function.

• Pourfour du Petit Syndrome: Causes mydriasis and exophthalmos.

Inner Ear

Structure and Function

• Comprises cochlea for sound perception and vestibular apparatus for balance.

Major Disorders

Otitis Interna

• Affects hearing and balance; can spread affecting cranial cavity, caused by infections or hematogenous spread.

Deafness

Congenital Deafness

• Most prevalent type in animals; associated with white coat color and cochleosaccular degeneration in breeds like Bull Terriers.

Acquired Deafness

• Types include conductive, neurological; causes include toxicity, acoustic trauma, inflammation, and ototoxicity from antibiotics/chemicals.

Vestibular Dysfunction

• Manifests as head tilt, ataxia, nystagmus; can be central (brain) or peripheral (inner ear), caused by infections, trauma, drugs.

Neoplasia of the Ear

• Squamous Cell Carcinoma: Common in white-eared cats.

• Ceruminous Gland Adenoma/Adenocarcinoma: Most common ear tumor.

• Auricular Melanoma: Aggressive in angora goats, can invade locally or metastasize.