Equine Endocrinology

Question 1

What is the most common endocrine disorder in horses?

Answer 1

Pituitary Pars Intermedia Dysfunction (PPID)

Question 2

What is the most important risk factor associated with PPID in horses?

Answer 2

Age - Typically 15 to 20 years old

Question 3

What is Hirsutism?

Answer 3

Excessive hair growth

Question 4

What clinical signs are associated with PPID?

Answer 4

Hirsutism, PU/PD, Hyperglycemia, Chronic Intermittent Laminitis, Muscle Wasting

Question 5

How do we diagnose PPID?

Answer 5

Clinical Signs

Dexamethasone Suppression Test

Baseline ACTH

Question 6

How does a dexamethesone suppession test work?

Answer 6

In a normal patient, cortisol tells the pituitary to stop producing ACTH. This reduced ACTH should tell the adrenal glands to stop producing cortisol. Dexamethasone has the same effect on the pituitary. In PPID, the pituitary gland continues to produce ACTH, regardless of the presence of cortisol/dexamethasone. Therefore, cortisol levels should remain constant both before and after (8-12 hours) administration of dexamethosone.

Question 7

What is the primary medical treatment prescribed for PPID?

Answer 7

Pergolide - A dopamine agonist that suppresses the production of ACTH. This is a lifelong treatment.

Question 8

If pergolide isn’t sufficient in treatment of PPID, what additional medication can be prescribed?

Answer 8

Cyproheptadine - A seratonin antagonist.