Large Animal Endocrinology

Question 1

What happens in Pituitary Pars Intermedia Disorder in horses

Answer 1

There is a loss of dopaminergic innervation to the pars intermedia of the anterior pituitary causing hyperplasia or adenoma (because dopamine usually inhibits growth of the pituitary) which causes an increase in ACTH which causes the adrenal gland to release more cortisol

Question 2

What are the clinical signs of PPID in horses

Answer 2

Often older (>15 years), Hypertrichosis (excess hair) or abnormal shedding, sweating disorders, weight loss or loss of muscle mass, Recurrent laminitis

Question 3

What are common biochemical changes in a horse with PPID

Answer 3

Stress leukogram, hyperglycemia and hyperinsulinemia, increased liver enzymes, maybe glucosuria

Question 4

What is the best way to diagnose PPID in a horse

Answer 4

Clinical Judgement! Especially hair coat abnormalities- most sensitive

Question 5

Can you use basal cortisol to test for PPID

Answer 5

No it is useless

Question 6

What is the problem with testing ACTH in horses

Answer 6

You can’t do an ACTH stim but you can try to measure the basal rates however there are seasonal reference ranges and stress effects it (horses trailered in), differences in reference ranges based on closeness to equator, need to run sample quickly…

Question 7

What is a test we can use for diagnosing PPID

Answer 7

TRH stimulation test- the premise being that TRH will increase the amount of ACTH released from the pituitary in an exaggerated amount (>200pg/ml) but hard to get TRH for a normal vet

Question 8

What do you use to manage PPID in horses

Answer 8

Pergolide which is a dopamine agonist to replace the lost dopamine, but the neurons keep dying so over time the dose will have to be increased

Question 9

What are some clinical signs of equine metabolic syndrome

Answer 9

Adiposity (regional or generalized fat), Laminitis, insulin dysregualtion (hyperinsulinemia- too much insulin in the blood)

Question 10

How do you test for EMS

Answer 10

You do an oral sugar test- give sugar and then measure insulin 60-90 minutes after. If there is an exaggerated insulin response (>/= 45 uIU/mL) then EMS is likely

Question 11

What are the treatment goals and management for EMS

Answer 11

reduce adipose tissue stores, manage the insulin resistance, and manage the laminitis
Diet- Use hay, low starch and no grain diets with limited/no pasture
Exercise
You can also try levothyroxine to make a little hypertyroid to help them lose weight or we can try metformin

Question 12

How common is equine hyperthyroidism and what does it look like

Answer 12

It is rare but it looks just like cats- weight loss and behavior changes

Question 13

Do horses get hypothyroidism

Answer 13

It is very rare it is probably EMS because when we give them hypothyroidism experimentally it is not the same symptoms as what we see when “hypothyroidism” is diagnosed (use levothyroxine for weight loss in EMS horses not for hypothyroidism)

Question 14

What are the common type of endocrine disorders that ruminants get

Answer 14

Disorders of energy metabolism and disrupted electrolyte homeostasis

Question 15

What happens to put a ruminant in a negative energy balance and what is the result

Answer 15

The glucose demand exceeds the intake/synthesis. Often because of milk production, pregnancy, or disease

Question 16

How are the ways ATP can be formed

Answer 16

From glucose, ketone, or lipids
glucose–> 2 pyretic acid –> 2 acetyl-CoA
Ketones–> 2 Acetyl-CoA
Lipids–> ketones or FFA + glycerol–> 2 acetyl- CoA
2 Acetyl-CoA go into the Krebs cycle to form ATP

Question 17

T/F all diary cattle in early lactation are ketogenic

Answer 17

True (subclinical ketosis)

Question 18

What does a cow in clinical ketosis look like and when does it usually occur

Answer 18

They usually present with a decreased milk production and inappetence within 6 weeks of calving

Question 19

What cows usually get clinical ketosis after calving

Answer 19

the highest milk producers