Pituitary Pars Intermedia Dysfunction Flashcards
________________ neurons degenerate with age
dopaminergic
what does pars intermedia normally secrete?
alpha melanocyte-stimulating hormone
corticotropin-like intermediate peptide
what does hyperplasia/neoplasia of the melanotrophs of the pars intermedia lead to?
excessive POMC production
what are the clinical signs of PPID?
older equid
hypertrichosis
muscle loss
increased susceptibility to disease
PUPD
laminitis
what is hypertrichosis?
delayed shedding of winter hair coat
longer than normal hairs in patches
eventually long curly coat
what diseases is the hoof more prone to with PPID?
sole abscesses
white line disease
what do ACTH and cortisol inhibit?
anti-diuretic hormone action
which horses with PPID are at higher risk of laminitis?
those with insulin dysregulation
plasma ACTH is ____________ with PPID
increased
what test is used for early PPID?
TRH stimulation test
what do TRH receptors on melanotrophs in the pars intermedia secrete in response to TRH given IV?
ACTH
what are the side effects of TRH?
yawning
coughing
licking
lip smacking
flehmen response
what is pergolide?
dopamine agonist
what is the first treatment option for PPID?
pergolide
why should you measure ACTH prior to initiating treatment?
to monitor the dose going forward
what does pergolide prevent in pregnant mares?
lactation
what does vitamin E help with?
oxidative degeneration of dopaminergic neurons
which horses with PPID should be put on a low-sugar diet?
high risk of laminitis: insulin dysregulation
what is the pars intermedia controlled by?
dopaminergic neurons from hypothalamus
how do fewer dopaminergic neurons lead to adenomas?
less dopamine: pars intermedia more active
leads to adenoma
what do the pars distalis and pars intermedia produce?
prohormone proopiomelanocortic (POMC)
what does ACTH stimulate that leads to hypertrichosis?
hair growth
loss of seasonal changes in alpha-MSH
what does muscle loss look like?
epaxial muscles: loss topline
loss abdominal muscle mass/strength and heavy viscera- rounded
how does PPID lead to immunosuppression?
reduced neutrophil function
why is polyuria/polydipsia a sign of PPID?
ACTH and cortisol inhibit anti-diuretic hormone action
what are the signs of early PPID?
decreased performance
delayed shedding of winter hairs
increased caloric demands
loss of muscle mass
deterioration of glucose and insulin status in EMS patient
when is basal ACTH concentration reliable for diagnosing PPID?
if PPID advanced
how does pergolide treat PPID?
interacts with dopamine receptors on melanotrophs in pars intermedia: inhibit
decreases secretion of ACTH and other hormones
when should you measure ACTH after starting pergolide?
30 days: increase dose if still above normal
what can be added along with pergolide in advanced cases?
ciproheptidine
