PPID (Yr 4) Flashcards
what does PPID stand for?
pituitary pars intermedia dysfunction
what tiggers the function of the pars intermedia?
neurotransmitters (dopamine)
what cells make up the pars intermedia?
melanotrophs
what is the main neurotransmitter that acts on the melanotrophs of the pars intermedia?
dopamine
what is the overall pathophysiological cause of PPID?
loss of dopamine inhibition on the pars intermedia
what is the general effect of dopamine?
inhibitory
what does loss of dopamine inhibition mean for the pars intermedia?
excess hormones being produced (ACTH)
hyperplasia or adenomatous change to pars intermedia
what is the main hormone produced by the pars intermedia?
ACTH
how old do horses develop PPID?
usually >15 years old (rarely less than 10)
what is the only predisposing factor for PPID?
age (older than 15)
what is the most specific clinical sign of PPID?
hypertrichosis (hirsutism) - delayed/abnormal shedding to thick curly coat
what are the clinical signs of PPID?
hypertrichosis (hirsutism)
laminitis
weight loss/redistribution
wasted epaxial muscles and pot belly
bulging supraorbital fat pad
lethargy
sweating
PUPD
why is important to confirm PPID with a diagnostic test?
treatment is lifelong/expensive
prognosis
monitor response to therapy
determine if insulin dysregulation is present (poses laminitis risk)
what tests can be used to diagnose PPID?
basal ACTH
ACTH response to TRH (rarely used)
what are the specific requirements when taking a blood sample for basal ACTH?
don’t do when stressed (after transport)
collect in purple EDTA tube
separate and chill within 3 hours
what should be used for the interpretation of a PPID test if the horse has clear clinical signs and is older than 15?
use more sensitive lower values to rule in disease unless below the threshold
what should be used for the interpretation of a PPID test if the horse has few clinical signs and isn’t the correct age?
use the upper values to rule PPID out
what is the high threshold test used for in PPID?
high specificity (95%) to rule out disease unless above the threshold
what is the lower threshold test used for in PPID?
high sensitivity (95%) to rule in disease unless above the threshold
if the basal ACTH test comes back inconclusive, what should be done?
retest the horse at a later date, while treating any clinical signs such as laminitis
what is the treatment for PPID?
pergolide
when a horse is on treatment for PPID, what needs to be done?
baseline endocrine levels (ACTH, insulin, glucose) before starting treatment
document appetite, hair cot, water intake, BCS, laminitis, demeanour
monitor throughout treatment (especially in first month)
what is the prognosis for PPID?
lifelong treatment but very successful and they can return to full athletic ability
how is hypothyroidism tested for?
TRH stimulation then measure T3 and T4 four to five hours later
