Pituitary Pars Intermedia Dysfunction

Question 1

________________ neurons degenerate with age

Answer 1

dopaminergic

Question 2

what does pars intermedia normally secrete?

Answer 2

alpha melanocyte-stimulating hormone
corticotropin-like intermediate peptide

Question 3

what does hyperplasia/neoplasia of the melanotrophs of the pars intermedia lead to?

Answer 3

excessive POMC production

Question 4

what are the clinical signs of PPID?

Answer 4

older equid
hypertrichosis
muscle loss
increased susceptibility to disease
PUPD
laminitis

Question 5

what is hypertrichosis?

Answer 5

delayed shedding of winter hair coat
longer than normal hairs in patches
eventually long curly coat

Question 6

what diseases is the hoof more prone to with PPID?

Answer 6

sole abscesses
white line disease

Question 7

what do ACTH and cortisol inhibit?

Answer 7

anti-diuretic hormone action

Question 8

which horses with PPID are at higher risk of laminitis?

Answer 8

those with insulin dysregulation

Question 9

plasma ACTH is ____________ with PPID

Answer 9

increased

Question 10

what test is used for early PPID?

Answer 10

TRH stimulation test

Question 11

what do TRH receptors on melanotrophs in the pars intermedia secrete in response to TRH given IV?

Answer 11

ACTH

Question 12

what are the side effects of TRH?

Answer 12

yawning
coughing
licking
lip smacking
flehmen response

Question 13

what is pergolide?

Answer 13

dopamine agonist

Question 14

what is the first treatment option for PPID?

Answer 14

pergolide

Question 15

why should you measure ACTH prior to initiating treatment?

Answer 15

to monitor the dose going forward

Question 16

what does pergolide prevent in pregnant mares?

Answer 16

lactation

Question 17

what does vitamin E help with?

Answer 17

oxidative degeneration of dopaminergic neurons

Question 18

which horses with PPID should be put on a low-sugar diet?

Answer 18

high risk of laminitis: insulin dysregulation

Question 19

what is the pars intermedia controlled by?

Answer 19

dopaminergic neurons from hypothalamus

Question 20

how do fewer dopaminergic neurons lead to adenomas?

Answer 20

less dopamine: pars intermedia more active
leads to adenoma

Question 21

what do the pars distalis and pars intermedia produce?

Answer 21

prohormone proopiomelanocortic (POMC)

Question 22

what does ACTH stimulate that leads to hypertrichosis?

Answer 22

hair growth
loss of seasonal changes in alpha-MSH

Question 23

what does muscle loss look like?

Answer 23

epaxial muscles: loss topline
loss abdominal muscle mass/strength and heavy viscera- rounded

Question 24

how does PPID lead to immunosuppression?

Answer 24

reduced neutrophil function

Question 25

why is polyuria/polydipsia a sign of PPID?

Answer 25

ACTH and cortisol inhibit anti-diuretic hormone action

Question 26

what are the signs of early PPID?

Answer 26

decreased performance
delayed shedding of winter hairs
increased caloric demands
loss of muscle mass
deterioration of glucose and insulin status in EMS patient

Question 27

when is basal ACTH concentration reliable for diagnosing PPID?

Answer 27

if PPID advanced

Question 28

how does pergolide treat PPID?

Answer 28

interacts with dopamine receptors on melanotrophs in pars intermedia: inhibit
decreases secretion of ACTH and other hormones

Question 29

when should you measure ACTH after starting pergolide?

Answer 29

30 days: increase dose if still above normal

Question 30

what can be added along with pergolide in advanced cases?

Answer 30

ciproheptidine