Endocrine Pathology
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- How do pituitiary cysts form?
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Develop from either:
Remnants of craniopharyngeal duct OR cystic dilation of the pituitary cleft. - What is the pathogenesis of Pituitary Juvenile (panhypopituitarism) Dwarfism?
- Failure differentation cell of oropharyngeal ectoderm of Rathke's pouch to hormone-secreting cells of pars distalis --> cyst formation --> compression of other portions of pituitary --> panhypopituitarism
- What breed does this most commonly affect? What are the gross lesions?
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German Shepard Dog
Small in size, coyote appearnce to head --> long ears - What is the cause of suppurative inflammation in the pituitary gland.
- Hematogenous spread of ruputred hepatic abscesses in cattle.
- Describe the lesion associated with non-suppurative (lymphocytic) inflammation of the pituitary gland.
- Extension of encephalitis into the neurohypophysis. Infiltration of lymphocytes and plasma cells.
- What is the common neoplastic disease of the pituitary gland?
- Corticotroph adenoma that may involve the pars intermedia or pars distalis in horses and dogs AND adenoma of the pars intermedia
- What lesions are associated with corticotroph adenomas?
- Pituitary mass and bilateral adrenal cortical hyperplasia.
- What lesions are associated with adenoma of the pars intermedia in horses?
- Usually large lesion that produces clinical syndrome of hirsutism, polyuria, polydypisa
- What lesions are associated with adenoma of the pars intermedia in dogs?
- Usually small and may be functionally inactive or produce Cushing's disease, diabetes insipidus or hypopituitarism.
- What is diabetes inspidius?
- Syndrome of polyuria and polydypsia from either lack of adequate ADH (hypophyseal form) or lack of renal response to hormone (nephrogenic form)
- What lesions are assoicated with diabetes insipidus?
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Pituitary neoplasms
Pituitary cysts
Post-traumatic hemorrhage - List two congential anomalies of the adrenal gland.
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Accessory cortical nodules: extracapsular masses of cortical tissue that may become prominent with hyperplasia and mistaken for neoplasia.
Hypoplasia: seen with congenital pituitary aplasia. - What are 3 causes of adrenal cortical atrophy?
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Hypopituitarism (lack of ACTH)
Exogenous corticosteroids (feed-back suppression)
Idiopathic in dogs (possibly immune-mediated) - What are the lesions of adrenal cortical atrophy?
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Thin shell of cortex
Decreased size and weight - What are the causes of adrenal cortical hyperplasia?
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ACTH-producing pitutiary chromophobe adenoma
Idiopathic hyperplasia (esp. poodles) - Describe the lesions of adrenal cortical hyperplasia.
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Thick, yellow cortex
May be nodular
Increased size and weight
Proliferation of zona fasciculata - What are causes of adrenal cortical necrosis in dogs?
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Idiopathic
Adrenocorticolytic drugs --> selectively toxic for zona fasiculata and reticularis - What are the lesions of adrenal cortical necrosis in the dog?
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Cortical necrosis, fibrosis and atrophy if chronic.
May produce Addison's Disease - List the causes of congestion and hemorrhage in the adrenal gland.
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Septicemia/Endotoxins
Shock
Stress - What can cause infarction of the adrenal glands?
- Endothelial damage --> thrombosis caused by septicemia (Salmonellosis in horses) and toxemia (volvulus in horses)
- Where are lesions of infarction localized in the adrenal gland?
- Red wedge shaped lesion located in the cortex.
- List and describe the three neoplasms found in the adrenal gland.
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Cortical Adenoma: dogs and ferrets, encapsulated, expansive growth
Cortical Adenocarcinoma: Dog, ferret, cattle, occassionally functional (Cushings-like), invasive (Posterior VC, Aorta), metastasizes to liver and lung
Pheochromocytoma: Dog and bulls with C-cell tumors, slow growing, invasive and usually non-functional. Can metastisize to lung and liver - List two congenital anomolies of the thyroid gland.
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Cysts (colloid filled)
Accessory glands (found anywhere between tongue and heart) - What are the 3 causes of thyroid atrophy?
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Hypopituitarism
Idiopathic
Aging - Describe the lesion of thyroid atrophy?
- Decreased size and weight, small amount of pale eosinophilic colloid, thin acinar epithilum, replacement by adipose tissue
- List the three causes of thyroid hyperplasia.
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Iodine deficiency
Idiopathic
Deficient synthesis of hormone (consumption of goitrogens/genetic enzyme deficiency/Excess iodine) - Describe the pathogenesis of diffuse hyperplastic goiter.
- Blocked or decreaed thryoxine --> excess TTH (TSH) production --> increased number of follicle cell pseudopodia and cells --> hyperplasia of follicle cells
- Describe the gross and histologic lesions of diffuse hyperplastic goiter.
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Gross: bilaterally enlarged, dark red, firm
Histo: tall follicle cells, little colloid, "resorption vacuoles" in colloid - Describe the pathogenesis of colloid "involutionary" goiter.
- Deficiency of thryroid hormone --> increased TTH (TSH) --> follicle cell hyperplasia --> increased colloid and thyroid hormone --> decreased pitutiary TTH (TSH) --> decreased endocytosis of colloid by follicular cells with continued colloid synthesis and excess colloid accumulation --> BIG follicles
- What are the gross and histologic lesions of colloid goiter?
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Gross: bilaterally enlarged, translucent on section, light color
Histo: flattened follicular cells, abundant colloid, BIG follicles - What is the cause of lymphocytic thyroiditis in dogs?
- Immune-mediated --> important cause of hypothyroidism
- What are the lesions associated with lymphocytic thyroiditis in dogs?
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Gross: pale, enlarged or atrophic
Histo: Extensive infiltrates of lymphocytes, plasma cells and macrophages --> replacement fibrosis eventually - List and describe the two most common neoplastic diseases of the thyroid gland.
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Thyroid Adenoma: (1/3 of thryoid tumors) in dogs and horses --> well circumscribed mass, may cause hyperthyroidism in aged cats along with carcinoma or multinodular hyperplasia
Adenocarcinoma: (2/3 of cases) in dogs and horse --> extensive vascular invasion, only rarely functional - What clinical expressions of disease are assoicated with hyperparathyroidism?
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Fibrous osteodystrophy
Hypercalcemia - What are the clinical expression of disease with hypoparathyroidism?
- Hypocalcemic tetany
- What are the causes of parathyroid hyperplasia?
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Primary idiopathic: functional parathyroid adenoma
Secondary to chronic renal disease (deficiency of renal 1-alpha-hydroxalase --> deficiency of Vitamin D3) OR (phosphate retention --> hyperphosphotemia --> decreased blood calcium levels)
Secondary to feeding high-phosphorus:low-calcium diets
Secondary to vitamin D deficiency
Tertiary to anal sac carcinoma or lymphosarcoma - What lesions are associated with hyperparathyroidsim?
- Increased size and weight of glands, fibrous osteodystrophy in skeleton and soft tissue mineralization (metastatic)
- What is the sequelae of hyperparathyroidism?
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Fractures
Metastatic mineralization - What is the common neoplastic disease of the parathyroid gland?
- Parathyroid adenoma --> encapsulated mass that may be functional (hyperparathyroidism)
- What are the causes of diabetes mellitus?
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Idiopathic (dog, vacoulated islet cell)
Chemical Toxin (Alloxan, STH)
Chronic pancreatitis/pancreatic necrosis (dog) - What are the pancreatic lesions assoicated with diabetes mellitus?
- Islet cell necrosis, amyloid deposits in islets, hyaline change in islets, chronic inflammation, atrophy and fibrosis of pancreas, ductal epithelium vacuolation from glygogen accumulation
- What are extrapancreatic lesions assoicated with diabetes mellitus?
- Fatty change in the liver and kidneys, glycogen accumulation in the liver and kidneys, cataracts, microangiopathy (kidney and retina)
- What is the pathogenesis of diabetes mellitus?
- Decreased insulin production --> glucose unable to enter some tissue --> hyperglycemia --> mobilization of fats for energy --> ketosis, acidosis --> coma
- What is the pathogeneisis for diatebetes cataract formation?
- Lens uses glucose via Kreb's cycle --> excess glucose --> shunts to sorbitol synthesis --> excess sorbitol increases lens osmotic pressure --> increased uptake of water --> hydropic degeneration and rupture of lens fibers --> cataract
- What is the most common neoplastic disease of the endocrine pancreas?
- Islet cell tumor "insulinoma" --> single or multiple gray firm masses that may be functional and produce hyperinsulinism and hypoglycemia (insulin shock)