19 - Equine Cushing's: PPID

Question 1

1. what is the path?

Answer 1

1. dopaminergic neurons in hypothalamus degen and lose fx -> loss of inhibition of PPI -> ^ hormone secretion

Question 2

(PPI)

1. what is the single endocrine cell type?
2. make what?
3. which is a precursor for what?

Answer 2

1. melanotropes
2. POMC (pro-opiomelanocortin)
3. ACTH

Question 3

1-7. name 7 Cx assoc with PPID

Answer 3

1. abnormal shedding
2. acute/chronic laminitis
3. muscle wasting
4. insulin resistance
5. abnormal fat
6. PU/PD
7. immunosuppression

Question 4

(diagnosis)

1. is measuring base cortisol useful?
2. why run tests?

Answer 4

1. no!
2. Testing is needed to identify horses at earlier stages of PPID development, when classical signs are absent

Question 5

(Dx)

(dexamethasone supression test)

1. measure cortisol pre/19 hours post Dex IM
2. what happens if normal?
3. if abnormal?
4. what are the negatives of ths?

Answer 5

2. dramatic corticol suppression
3. reduced/absent supression
4. sensitive only in advanced PPID, can cause laminitis

Question 6

(Dx)

(Endogenous ACTH)

1. sens/spec similar to DST
2. normal value?
3. abnormal?

Answer 6

2. < 30
3. > 35

Question 7

(Combined TRH/ACTH Test)

1. why is it good?
2. what is the procedure?
3. what happens if PPID?

Answer 7

1. sens in early cases
2. Draw blood for ACTH -> give TRH -> measure ACTH in 10 min
3. dramatic elevation in ACTH

Question 8

1. What is the best treatment?
2. what is it/how does it work?

Answer 8

1. Pergolide Mesylate
2. D2 receptor antagonist -> restore inhibition