Pathology of Endocrine System Flashcards
What is the definition of Primary Hyperfunction?
Cells of lesion autonomously synthesize and release hormone at an excess rate
e.g. primary hyperparathyroidism: adenoma or adenocarcinoma in the parathyroid gland
What is the definition of Secondary Hyperfunction?
Excess trophic hormone production in another organ
e.g Pituitary tumor increasing ACTH release and increasing cortisol production + release
What is the definition of Primary Hypofunction?
Reduced hormone secretion by an organ, can be due to:
- destruction of secretory cells of the organ: e.g. immune-mediated injury
- failure of normal development of the organ: e.g. Pituitary dwarfism
- biochemical defect in the synthesis pathway: e.g. Vitamin D dependent rickets in pigs
What is the definition of Secondary Hypofunction?
Interference with the secretion of trophic hormones
e.g. pituitary neoplasm that is non-functional (not releasing hormone) but is destroying surrounding secretory cells
What is another name for the Pars distalis of the Pituitary gland?
- Adenohypophysis
- Anterior pituitary
note: produces and releases the majority of the pituitary hormones: GH, Prolactin, LH, FSH, TTH, ACTH
Under control of the Hypothalamus via Releasing Hormones, which are secreted into the rostral hypophyseal artery
What is another name for the Pars nervosa of the Pituitary gland?
- Neurohypophysis
- Posterior pituitary
note: storage and secretory site of oxytocin and ADH
What are the potential underlying causes of Hypopituitarism of the pars nervosa specifically?
- Compression and destruction of the pars nervosa, infundibular stalk, or supraoptic nucleus in the hypothalamus
Can be due to neoplasia, cysts, inflammation, or trauma
What clinical signs would you expect to see with a disease in the pars nervosa?
- Diabetes insipidus: due to inadequate ADH production
- PUPD –> hypotonic urine
What are the potential underlying causes of Hypopituitarism of the pars distalis specifically?
- Aplasia: seen in Guernsey and Jersey cattle mainly, leading to a prolonged gestation. The fetus’ pituitary didn’t develop fully and therefore no ACTH is released to cause the cortisol surge needed for parturition
- Cysts: can lead to pituitary dwarfism
- Non-secretory neoplasia
- Inflammation: abscess or meningitis
What are the most common causes of hyperpituitarism?
- Functional adenomas, either in the pars distalis or the pars intermedia
e. g. Functional adenoma of ACTH-secretion, which stimulates both adrenal glands, leading to hyperplasia and Cushing’s disease
e. g. Functional adenoma of the pars intermedia. Occurs in horses. This functional adenoma produces excess pro-OMC peptides, leading to docility and a diminished response to pain
e. g. Functional adenoma of the pars distalis, leading to hypersecretion of GH and somatotropin –> Acromegaly in cats
What hormones does the Zona Glomerulosa release?
What is the most common dysfunction/ disease of this zone?
- Releases mineralcorticoids: aldosterone + deoxycorticosterone independent of ACTH
These hormones are responsible for Na + water reabsorption, and K secretion from the kidneys
- Most commonly: hypofunction = Addison’s Disease
What hormones does the Zona Fasciculata release?
What is the most common dysfunction/ disease of this zone?
- Releases glucocorticoids: cortisol, cortisone and corticosteroid
Responsible for glucogenesis, lipolysis, protein catabolism and anti-inflammatory
- Most commonly: hyperfunction = Cushing’s Disease
What hormones does the Zona Reticularis release?
What is the most common dysfunction/ disease of this zone?
- Releases sex hormones
No significant malfunctions
You notice the adrenal glands of an older dog/ cat/ horse have focal enlargements on U/S, but the dog does not present with any clinical signs, what could this be?
Nodular hyperplasia
Non-functional, often an incidental finding, usually find multiple nodules on both adrenal glands and they can be up to 2cm wide
What are the possible causes of Primary hypoadrenocorticism?
- Idiopathic adrenocortical atrophy: thought to be an auto-immune disease
- Metastatic Neoplasia
- Adrenal cortex necrosis/ haemorrhage: common in DIC, viral infections, overexertion or stress in wild animals
- Fungal infections or Tuberculosis
What are the possible causes of Secondary hypoadrenocorticism?
- Hypopituitarism: disease in the pituitary gland
- Iatrogenic adrenocortical atrophy: overtreatment of Cushing’s, rapid withdrawal from steroids, use of progestagens
What is the function of the adrenal medulla?
- Production of catecholamines: epinephrine/ adrenaline
What is the most commonly seen disease of the adrenal medulla?
- Pheochromocytoma
A tumor of the chromaffin cells in the adrenal medulla - Seen in horses and dogs
- Usually malignant
What are the most common causes of Hypoparathyroidism?
Dogs:
- Lymphocytic parathyroiditis: immune-mediated disease leading to the destruction of the parathyroid (most common cause in dogs)
- Infarction/ inflammation
Cats:
- Iatrogenic: usually removal of the parathyroid during thyroid surgery
What are some causes of Primary Hyperparathyroidism?
- Functional parathyroid neoplasm: usually an adenoma, less likely a carcinoma
Surgery is usually curative
What are some causes of Secondary Hyperparathyroidism?
This is the excessive secretion of PTH in response to hypocalcemia
- Renal: increased retention of P, or a decrease in active Vitamin D leads to the increased P and decrease in Ca+ which overstimulates the production of PTH
- Nutritional: Diets high in Phosphorus (e.g. Bran) or Malabsorption of Ca+
What are some causes of Pseudo- Hyperparathyroidism?
This is a type of Paraneoplastic Syndrome
Tumors that cause this include:
- Lymphosarcoma
- Adenocarcinoma of the anal glands
- Multiple myeloma
- Any neoplasia that metastisizes to the bone and causes necrosis leading to Ca+ release
What are the possible causes and the most common cause of Hypothyroidism?
Dogs:
Most commonly
- Lymphocytic thyroiditis: an autoimmune reaction to thyroglobulin. There is a breed/ genetic predisposition in Goldens, Doberman Pinschers, Cocker Spaniels and Airedales
Less commonly:
- Bi-lateral non-functional thyroid neoplasia
- Pituitary disease e.g. Pituitary dwarfism
- Diffuse hyperplasia of the thyroid follicular cells: iodine deficiency or ingestion of goitrogenic compounds (clover, brassica, seaweed)
- Nodular hyperplasia in the thyroid glands: these are endocrinologically inactive in dogs and horses, EXCEPT in cats, which causes hyperthyroidism in cats
What are the possible causes and the most common causes of Hyperthyroidism in cats and dogs?
Cats:
- Functional Adenomas/ hyperplastic lesions
- Carcinomas are less likely
Dogs:
- Functional adenocarcinoma, BUT most are non-functional
- Adenomas are less likely
