Pituitary HAC equine Flashcards
List the corticotropes released by the pars distalis in horses
POMC
ACTH
B-lipotropin
List the melanotropes produced in the pars intermedia in horses
- POMC
- MSH
- CLIP
- B lipotropin
- ACTH
What is the role of MSH?
Regulate appetite, sexual behaviour and melanin production
What is the role of CLIP?
Modulate pancreatic exocrine function
What is the role of b-lipotropin?
Melanin production, steroidogenesis and lipolysis
What is the role of B-endorphin?
Behaviour-docility
What does PPID stand for?
Pituitary Pars Intermedia Dysfunction
What is PPID also known as?
Equine cushings disease
What causes HAC in horses?
Pars intermedia adenoma-> excessive production of POMC’s derived peptides-> hyperadrenocorticism
What inhibits the pars intermedia?
Dopamine- lack of inhibitory control permits the formation of adenomas
Which receptor inhibits the expression of POMC?
D2 (dopamine)
What affect does administration of TRH have on PPID cases?
Increases release of a-MSH
What are the clinical signs of PPID?
- Hirsutism (excess hair)
- Weight loss
- PU/PD
- Laminitis
Why does PPID cause hirsutism?
- Due to chronic elevation of MSH
- Pituitary compresses the hypothalamic thermoreg centre
- Increased production of androgens
Why does PPID cause laminitis?
- High glucocorticoid concentration
- Persistent hyperinsulinemia
Why does PPID cause PU/PD?
- ACTH/ cortisol inhibit ADH
- Hyperglycaemia and glucosuria= osmotic diuresis
Why does PPID cause weight loss?
- Abnormal fat deposits/ fat redistribution
- Glucocorticoids have a catabolic effect on the skeletal muscle
Why does PPPID results in increased docility/ lethargy?
Increased B-endorphin
Why do horses with PPID have an impaired response to infection?
- Because of elevated levels of immunosuppressive steroids
e. g. cortisol/ a-MSH, B-endorphin
How do you diagnose PPID?
Multiple tests including:
- Resting ACTH
- TRH stimulation test
- Insulin test
Describe how you would use POMC to diagnose PPID
-POMC is disproportionately high than ACTH in horses with PPID
