Pituitary Gland Flashcards
what’s the other name for the pituitary gland? where is it normally located?
hypophysis
sella turcica, a depression in the sphenoid bone
pituitary gland has a close anatomic relationship to the _____, _____, and ______.
optic chiasm, hypothalamus, brain
what are the two components of the pituitary gland?
- adenohypophysis (anterior pituitary)
- neurohypophysis (posterior pituitary)
what are the two components of the adenohypophysis?
- pars distalis
- pars intermedia
what does the pars distalis do?
variety of cells that produce trophic factors
each cell type is under the control of a releasing hormone from the hypothalamus
acidophils (GH, PRL), basophils (TSH, FSH, LH), chromophobes (ACTH)
what does the pars intermedia do?
melanotrophs = predominant cell (POMC –> MSH)
ACTH production in dogs
what does the neurohypophysis do?
oxytocin, ADH
neurons originate in the hypothalamus
what disorder of the neurohypophysis do we have to know?
diabetes insipidus
what are the two categories of disorders of the adenohypophysis, and what falls under each category?
- hypopituitarism
- aplasia & prolonged gestation
- pituitary cysts (Pituitary dwarfism)
- non-functional tumors that destroy the pituitary - hyperpituitarism –> functional (hormone-secreting) tumors
- corticotroph (ACTH-secreting) adenomas
- melanotroph adenomas of the pars intermedia
- somatotroph adenomas
why does hypopituitarism cause aplasia and prolonged gestation?
parturition requires intact hypothalamic-pituitary-adrenocortical axis
in regards to aplasia and prolonged gestation, what is an example of a cause of hypopituitarism and what does it result in?
Veratrum californicum (skunk cabbage)
ingestion day 14 of gestation causes a neural tube defect
numerous craniofacial defects (cyclopia)
aplasia or malformation of the adenohypophysis
poor little dude was born this way! what might his mother have done during gestation to make him like this?
ate Veratrum californicum on day 14 of gestation
what causes a pituitary cyst?
failure of the oropharyngeal ectoderm of Rathke’s pouch to differentiate into the pars distalis
what does a pituitary cyst cause?
juvenile panhypopituitarism (pituitary dwarfism)
what breed is predisposed to pituitary cysts and what does it do in that breed?
German shepherds (autosomal recessive)
failure to grow, retention of puppy coat
hypoadrenocorticism, hypothyroidism
the dog in the back is normal and the dog in the front is abnormal. they are from the same litter. what might be going on?
juvenile panhypopituitarism/pituitary dwarfism caused by a pituitary cyst
what’s the lesion?
pituitary cyst
nonfunctional pituitary neoplasms most often occur in what species?
dogs and cats
what are the clinical signs of nonfunctional pituitary neoplasms due to?
hypo function of pituitary and diminished target organ function
CNS compression
what are the clinical signs of a nonfunctional pituitary neoplasm that is caused by CNS compression?
weakness, ataxia, blindness, diabetes insipidus
what are the clinical signs of a nonfunctional pituitary neoplasm that is caused by hypo function of pituitary and diminished target organ function?
hypothyroidism
hypoadrenocorticism
gonadal atrophy in intact animals
what’s the lesion
nonfunctional pituitary adenoma
Corticotroph, or adrenocorticotropic hormone-secreting adenomas are common in what species?
dogs, increasingly cats
where do corticotroph or ACTH-secreting adenomas occur?
in the corticotroph cells of pars distalis or intermedia in dogs
corticotroph or ACTH-secreting adenomas cause what clinical syndrome? is this common?
hyperadrenocorticism (Cushing’s disease)
yes common - 85-90% of HAC due to pituitary tumors
what are the gross lesions of corticotroph or ACTH-secreting adenomas?
bilateral adrenocortical hypertrophy/hyperplasia (zona fasiculata and zona reticularis)
what’s the lesion?
corticotroph or ACTH-secreting adenoma
what is the most common pituitary tumor of horses?
melanotroph adenoma of the pars intermedia
what clinical syndrome does a melanotroph adenoma of the pars intermedia cause?
pituitary pars intermedia dysfunction (PPID)
true or false: PPID is the same as Cushing’s disease of horses
FALSE!
melanotroph adenomas of the pars intermedia are ____ tumors, meaning they cause ____ production of POMC and its derivatives.
functional, excessive
the clinical syndrome caused by melanotroph adenomas of the pars intermedia is mainly the result of what?
hypothalamic/neurohypopheal dysfunction
tell me some clinical signs of PPID in horses. you need to know the first one for sure.
hypertrichosis
polyphagia
hyperglycemia/glucosuria
PU/PD
weight loss of abnormal distribution of fat
intermittent hyperpyrexia
hyperhidrosis
laminitis
this is your horse Gordon. What is causing this clinical sign?
melanotroph adenoma of the pars intermedia causing pituitary pars intermedia dysfunction (PPID)
this is a horse skull. what is the lesion?
melanotroph adenoma of the pars intermedia
somatotroph adenomas are primarily in what species?
cats
what is acromegaly?
hyper secretion of growth hormone (GH) aka somatotrophin
true or false: somatotroph adenomas cause acromegaly
true
tell me how a somatotroph adenoma causes diabetes mellitus
- somatotroph adenoma
- hypersecertion of GH
- increased IGF-1 secretion by liver
- proliferation of ST and bony tissues AND insulin-resistant diabetes mellitus
feline hypersomatotropism caused by somatotroph adenomas can result in what clinical signs?
broad face, inferior prognathia, clubbed feet, plantigrade stance
what are the two forms of diabetes insipidus?
- hypophyseal or central form
- nephrogenic form
what is the hypophyseal or central form of diabetes insipidus ?
inadequate production of ADH
compression/destruction of the neurohypophysis or hypothalamus
what is the nephrogenic form of diabetes insipidus?
inability of target cells in kidney to respond to normal to increased levels of ADH
diabetes insipidus causes what important clinical sign?
inability to concentrate urine
produce large vols of dilute urine, PU/PD
