Equine Endocrine Disorders

Question 1

What is the most commonly diagnosed endocrine abnormality in the horse

Answer 1

Hyperadrenocorticism- PPID

Question 2

What cell type is in the pars intermedia

What does it produce?

Answer 2

Melanotrope
Produces POMC peptides which are cleaved into alpha melanocyte stimulating hormone, beta endorphin, and CLIP
Also a tiny bit of ACTH

Question 3

What cells are in the pars distalis?

What do they produce

Answer 3

Corticotropes

Produce ACTH

Question 4

What inhibits melanotrophs?

What stimulates them?

Answer 4

Dopamine inhibits

TRH stimulates

Question 5

What are other things that regulate pars intermedia

Answer 5

Seasons! Higher in the fall when the animal is preparing for winter

Question 6

What is the pathology of PPID

Answer 6

Hypertrophy, hyperplasia, and adenoma formation of pars intermedia resulting in 40 fold increase in POMC peptides. This results in damage to the hypothalamus from a big pituitary and LOSS OF DOPAMINERGIC INHIBITION

Question 7

What are clinical signs of PPID

Answer 7

Hypertrichosis
PU/PD
Laminitis- may be presenting complaint
Muscle wasting
Increased sweating
Increased appetite
Bulging eyes
Immunosuppression
Lethargy
Blindness/seizures/ataxia
Infertility

Question 8

What is the best indication for PPID

Answer 8

Hypertrichosis/hirusitism

Question 9

What are other diagnostic tests you may use

Answer 9

Baseline ACTH
TRH stimulation test
Dex suppression test- careful with laminitis

Question 10

What treatments are used for PPID

Answer 10

Pergolide- dopamine agonist
Cyroheptadine- serotonin antagonist
Supportive care

Question 11

What is equine metabolic syndrome

Answer 11

Horses with:
Insulin resistance
Obesity/regional adiposity
Prior or current laminitis
“Easy keeper”

Question 12

Diagnostic testing for EMS

Answer 12

Resting serum insulin concentration
Oral sugar test
Combined glucose-insulin test

Question 13

How to treat EMS

Answer 13

Manage obesity

Manage IR- levothyroxine, steroids, metformin and chromium picolinate

Question 14

How to measure hypothyroidism in horse

Answer 14

Administration of TRH or TSH

single baseline thyroid hormone measurement not affective

Question 15

What is SDF

Answer 15

Synchronous diaphragmatic flutter

Hypocalcemia causes depolarization of phrenic nerve in time with right atrium

Question 16

Clinical signs of SDF

Answer 16

Anxious breathing, thoracic muscle contractions “ticking” in time with hear

Question 17

Treatment of SDF

Answer 17

IV calcium- slow

Question 18

What other hypocalcemia illness could a horse get

Answer 18

Lactation tetany
Sepsis/endotoxemia
Blister beetle toxicosis- can be in alfalfa hay accidentally

Question 19

Clinical sings of blister beetle toxicosis

Answer 19

Widespread mucosal irritation and ulceration of GI, renal, CV, and nervous system
Sweating, SDF, muscle fasciculations, caridac arrhythmias

Question 20

Treatment of blister beetle toxicosis

Answer 20

IV fluids, charcoal or mineral oil, IV calcium

Question 21

What causes secondary nutritional hyperparathyroidism in the horse

Answer 21

Diets with lots of P and low Ca

Can also occur with ingestion of oxalates

Question 22

How does nutritional secondary hyperparathyroidism cause hypercalcemia

Answer 22

The low dietary ca causes parathyroid hyperplasia and stimulate PTH secretion

Question 23

Clinical signs of snhpt

Answer 23

Enlarged head, widened maxilla, pathologic fractures and bone remodeling

Question 24

How to diagnose snhpt

Answer 24

History, serum ca is normal or low, serum P is normal/high