Pituitary Gland Pathology Flashcards
what are the three possible outcomes of endocrine pathology
- increased function
- decreased function
- no change in function
what is the progression of endocrine disorders of growth
hyperplasia –> adenoma –> carcinoma
hyperplasia
non-neoplastic proliferation; still has some regulatory capacity
diffuse hyperplasia
growth of the entire organ (hyperplasia and hypertrophy)
nodular hyperplasia
“adenomatous”
multiple well-demarcated nodules that are NOT encapsulated
difficult to differentiate from adenomas
adenoma
benign neoplasia
solitary, thinly encapsulated, well-demarcated masses
often compresses surrounding tissues
carcinoma
large, invasive, metastatic, malignant neoplasia
rare
what is the main difference in pituitary anatomy of cows
has a layer of dura mater over top of the pituitary gland
prevents dorsal deviation of the pituitary into the brain
histology of pars distalis
dark pink staining region
acidophils: dark pink cells
basophils: blue cells
chromophobes: non-staining cells
what is the function of the pars distalis
secretes the majority of trophic pituitary hormones
LH, FSH, GH, TSH, ACTH/MSH, prolactin
histology of pars nervosa
light pink staining region (glia)
function of the pars nervosa
secretes ADH, oxytocin
histology of pars intermedia
blue/basophilic staining region
junction between pars distalis and nervosa
contains Rathke’s pouch (not in horses)
function of pars intermedia
secretes ACTH/MSH in dogs and horses
four main categories of pituitary pathology
- juvenile panhypopituitarism
- failure of fetal endocrine function
- diabetes insipidus
- acquired diseases
juvenile panhypopituitarism
congenital failure of the pars intermedia and distalis to develop
what is the main lesion associated with juvenile panhypopituitarism
proportionate dwarfism
low GH, FSH, LH, TSH
does ACTH increase/decrease/no change with juvenile panhypopituitarism
no change (normal)
what are associated lesions with juvenile panhypopituitarism
- truncal alopecia (non-inflammatory/pruritic)
- delayed permanent teeth
- cystic rathke’s pouch
what species is juvenile panhypopituitarism most common in
dogs
failure of fetal endocrine function
congenital failure of fetal pituitary function
what is the main outcome associated with failure of fetal endocrine function
delayed parturition
loss of dam ACTH –> lack of signaling to uterus –> failure to produce PGF2a –> failure to signal parturition –> prolonged gestation
what species is failure of fetal endocrine function most common in
ruminants
what are common causes of failure of fetal endocrine function
congenital:
1. genetic
2. infectious
3. toxic
infectious causes of failure of fetal endocrine function
BVDV - leads to hydranencephaly (cortex lobes replaced by CSF), which causes pituitary and hypothalamic dysfunction
toxic causes of failure of fetal endocrine function
sheep: skunk cabbage ingestion by the dam at a certain period in gestation
- interferes with fetal signaling
- malformation of the fetal brain and pituitary
- failed endocrine function
concurrent lesion: cyclopia
diabetes insipidus
vasopressin (ADH) deficiency OR resistance
what is the main outcome of diabetes insipidus
increased production of hypotonic urine (USG <1.005)
what are the two causes of diabetes insipidus
- neurogenic: leads to decreased production of ADH
- nephrogenic: leads to decreased response to ADH
what are examples of acquired pituitary diseases
- hypophysitis
- disorders of growth
- equine pituitary pars intermedia dysfunction
hypophysitis
inflammation of the pituitary gland
suppurative infiltrate (neutrophils) in pars distalis/intermedia
disorders of growth
hyperplasia or neoplasia (adenoma)
what species are disorders of growth most common in
dogs, cats, horses, pigs
what are the possible outcomes of disorders of growth
- hyperpituitarism
- hypopituitarism
- no change
what is the most common outcome and clinical signs of ACTH secreting pituitary gland adenomas
hyperadrenocorticism
increased ACTH –> increased cortisol production from adrenal
clinical signs: PU/PD/PP, panting, redistribution of fat (pot belly), truncal alopecia
what is the most common outcome of GH secreting pituitary gland adenomas
diabetes mellitus
equine pituitary pars intermedia dysfunction (EPPID)
most common endocrinopathy of horses
hyperplasia or adenoma of the pars intermedia
pathogenesis of EPPID
- injury to dopaminergic cells
- imbalance of dopamine and serotonin
- serotonin predominates
- hyperplasia of melanotrophs
- increase in POMC derivative hormones
what are the POMC derivative hormones
ACTH, MSH, endorphins
clinical signs of EPPID
hirsutism (failure to shed coat leading to fluffy coat)
PU/PD
laminopathy
fever
polyphagia
hyperhidrosis
secondary lesions associated with EPPID
- compression atrophy of hypothalamus
- diffuse hyperplasia of adrenal cortex (from ACTH overproduction)
