Pituitary Gland Pathology Flashcards
What is autocrine signalling?
Hormones are on the cell itself
What is an endocrine gland?
Organs/ Glands comprised of cells that synthesise, store, secrete and release signalling molecules into the blood
What in cells makes polypeptides/ glycoproteins?
Ribosomes and the ER
What is the primary site of action for polypeptide hormones?
The plasma membrane as they are H2O soluble
half life = minutes
What is the basis of steroid hormones?
Cholesterol based so they are lipid soluble- can diffuse through the cell membrane
T 1/2 = hours
function as nuclear receptors and transcription factors
What are catecholamines derived from?
Tyrosine derived
How is the pituitary formed embryologically?
Rathke’s pouch- they come together to form different parts of the pituitary
What are the two key concepts surrounding pituitary function?
- the anterior pituitary produces most of the endocrine TROPHIC hormones in the body
- the production of these hormones is under the control of releasing and inhibitory hormones produced by the hypothalamus
What three types of cells are in the pars distalis?
- acidophils- peptides
- basophils- glycoproteins
- chromophobes- corticotrophs
What cell type is in the pars intermedia?
Chromophobes
proopiomelanocortin-> ACTH, a-MSH, b-endorphins
What is the function of releasing hormones?
Stimulates the release of trophic hormones
What is the function of inhibitory hormes?
Inhibits the release of trophic hormones
What two hormones are produced by the posterior pituitary gland?
- Oxytocin
- ADH
What is the function of oxytocin?
Stimulates contraction of
myometrium, myoepithelium of
mammary gland
What is the function of ADH?
- Stimulates the insertion of aquaporins into the renal tubule epithelia
- increases urine osmolarity
- decreases plasma osmolarity
- arteriolar vasoconstriction
What is primary hyperfunction of the pituitary
- usually hypersecretion of a hormone
- typically neoplastic
What is secondary hyperfunction of the pituitary?
- increased trophic or releasing hormones
- or a decrease in inhibitroy hormones (more likely)
What is primary hypofunction of the pituitary?
- Destruction, lack of formation of the secretory cells or a deficiency in the synthesis of the hormone
What is Juvenile panhypopituitarism
Failure of oropharyngeal ectoderm to differentiate into the
adenohypophysis
autosomal recessive inheritance
primary hypofunction
What is juvenile panhypopopiturasim most common in?
German shephards
What does failure of proper pituitary development result in?
prolonged gestation and abnormal adrenal function
What is the hypophyseal form of central diabetes?
inadequate secretion of ADH
* occurs due to destruction of the neurohypophysis
* compression from anterior pituitary masses
What kind of hormones do acidophils secrete?
Peptide hormones
What kind of hormones do basophils secrete?
glycoproteins
What kind of hormones do chromophobes secrete?
Variable
What dog breed is juvenile panhypopituitarism most common in?
German Shephards
What is the Gross Pathology of Juvenile Panhypopituitarism?
- Normal until around 2 months
- Slow growth/ Retention of ‘puppy hair’
- Fox or Coyote like
- Delayed epiphysis closing
- lack of genital development
What does failure of proper pituitary development and signalling typically result in?
Prolonged gestation and abnormal adrenal function
What are the two ways you can get failure of foetal endocrine function?
- Genetic (aplasia of the adenohypophysis)
- Toxic (malformations of the CNS) including the hypothalamus
What does Cyclopamine (toxic principle in corn lillies) do to the CNS?
inhibits neural tube devlopment via impaired sonic hedgehog signalling
What is synopthalmia and what plant causes it?
- Clinical abnormality where both eyes are fused and can be seen centrally in the middle of the face
- Caused by corn lillies
What causes the hypophyseal form of DI neurohypophysis?
- Destruction of the neurohypophysis
- Compression from anterior pituitary masses
What causes the nephrogenic form of DI neurophyophysis?
- Inability to respond appropriately to ADH
- occurs during kidney damage, rarely inherited
What is the Clinical Presentation of DI neurohypophysis?
- Excretion of large volumes of hypotonic urine
- administration of ADH can be used to differentiate between hypophyseal and nephrogenic
What is the most common cause of cortisol excess in dogs?
Adenohypophysis adenoma
ACTH-secreting adenoma
What is a somatotroph?
GH secreting adenoma
What may a nonfunctional adenoma do?
may destroy the remaining pituitary gland via compression, resulting in trophic atrophy of target organs
What does equine Pituitary Pars Intermedaite dysfunction do?
Nodular hyperplasia and neoplasia of the pars intermedia
increases the PI hormones
What is the pathogenesis of Equine Pituitary Pars Intermedia dysfunction?
- Degeneration of hypothalamic dopaminergic neurons
- Loss of inhibition on the PI
- Hypertrophy/ hyperplasia
- Compression of the overlying hypothalamus
What is Hypophysitis?
Inflammation of the pituitary gland
What are some examples of polypeptides/ Glycoproteins?
- GH, PRL, ACTH, ADH, oxytocin
What are some examples of Steroids?
- Cortisol
- Androgens
- Aldosterone
Where do catecholamines/ iodothyronines act?
Act at plasma membrane surface or intranuclear
have a variable half ife
What are some examples of catecholamines?
epinephrin, norepinephrin, thyroxine
What is secondary hypofunction?
When the pituitary produces a decreased amount of a trophic hormone
What does the failure of pituitary development look like in cattle?
aplasia of the adenohypophysis
What does corn lily do to the CNS?
- malformation of the CNS including the hypothalamus
- Cyclopamine is the toxic principle
- inhibits neural tube development via sonci hedgehog signalling
What is the nephrogenic form of DI?
Inability to respond appropriately to ADH
occurs due to kidney damage- rarely inherited
What is the clinical presentation of the nephrogenic form of DI?
- excretion of large volumes of hypotonci urine (polyuria) with increased drining (polydipsia)
- administration of exogenous ADH
What is the most common cause of systemic cortsiol excess in dogs?
Cortocotroph adenoma
they must demonstarte metastasis
to be classified as pituitary carcinoma
What is the sequelae to corticotroph?
adrenal cortical hyperplasia
What does a somatotroph cause?
- Acromegaly (too much GH)
- reported in dogs, cats and sheep
What is hypophysitis?
inflammation of the pituiatry gland
