01 - equine cushings-like syndrome

Question 1

aka what?

Answer 1

pars intermedia dysfunction (PID)

Question 2

(role of the hypothalamus)

1. translator between CNS and pituitary gland
2. pars intermedia hyperplasia may be related to hypothalamic dysfx

Question 3

(pars intermedia)

1. tonic inhibition is via what?

Answer 3

1. dopamine

Question 4

(path)

1. funtional hypertrophy or hyperplasia of PPI
2. increased beta-endorphin, alpha-melaotropin, ACTH
3. initial loss of what inhibitory neurotransmitter?

Answer 4

3. dopamine

Question 5

(gross path)

1. pars intermedia grossly enlarged
2. also see bilateral adrenal gland hyperplasia (from increased ACTH)

Question 6

(signalment)

1. avg age?
2. sex predilection?
3. breed predilection?
4. ponies tend to get more than horses (not proven)

Answer 6

1. 19 years (range from 7-40)
2. no
3. no

Question 7

Cx

give the 5 main Cx

Answer 7

laminitis

PU/PD

hyperhidrosis

muscle wasting

hirsutism (85% of cases - most common clinical sign)

(additional: narcolepsy, neuro signs, wt loss, redistribution of fat, ^ appetite, recurrent infections, sinusitis, pneumonia, skin infection)

Question 8

(diagnosis)

1. min database
2. hx and cx
3. CBC - see what?
4. chem - usually normal - can sometimes see increases in what?

Answer 8

3. possible stress leukogram, neutrophilia, lymphopenia
4. ALP, lipids, glucose

Question 9

(diagnosis)

(resting cortisol)

1. usually normal
2. in normal horses usually higher in the morning and lowest in evening

PID horses lose this diurnal variation

Question 10

(diagnosis)

1. are T4 levels affected?

Answer 10

1. no

Question 11

(diagnosis)

1. what is the test of choice?

Answer 11

dexamethasone suppression test

Question 12

(diagnosis)

(endocrine fxn testing)

(dexamethasone suppression test)

1. test of choice
2. either overnight or standard test
3. if normal would expect to see dramatic reduction in cortisol level
4. limitations: normal cortisol much higher in fall! age/gender/gestation

Question 13

(diagnosis)

(endocrine functino testing)

(thyroid releasing hormone (TRH) stimulation test)

1. poor specificity, but gaining in popularity
2. in horses with PID cortisol and insulin should ^ in 15 minutes and stay elevated for 90
3. mechanism is unclear

Question 14

(diagnosis)

(endocrine function testing)

(ACTH stimulation test)

1. doesn’t adequately distinguish between normal and cushing horses

Question 15

(diagnosis)

(endocrine function testing)

(glucose/insulin tolerance test)

1. PID horss often have poor regulatory mechanisms and are insulin resistant
2. effected horses have increased insulin levels

Question 16

(diagnosis)

(endocrine fxn testing)

(endogenous ACTH)

1. ponies greater than what suggest pituitary adenoma?
2. horses?

Answer 16

1. > 27 pg/mL
2. > 50 pg/mL

Question 17

(treatment)

1. careful mgmt of 2° complications!
2. euglycemic patients have a very good prog!

Question 18

(drug tx)

1. what two drugs are used?

Answer 18

1. cyproheptadine
2. pergolide

Question 19

(drug tx)

(cyproheptadine)

1. what is it?

Answer 19

1. serotonin antagonist

Question 20

(drug tx)

(pergolide)

1. what is it?
2. downside?
3. may take a few weeks to determine if effective
4. possible side fx?

Answer 20

1. dopamine antagonist
2. $$$
3. colic and laminitis (if these occur decrease dose)