Endocrine - equine Flashcards
What are the 3 endocrinopathies of horses? How common are they?
Pituitary pars intermedia dysfunction - common
Hypothyroidism - rare
Granulosa-theca cell tumour
What is PPID?
Decrease in production of dopamine from hypothalamus
Decrease in inhibition of pituitary so pituitary adenoma
Overproduction of POMCs (pro-opiomelanocortins)
What are the clinical signs of PPID?
Long curly coat
Insulin resistance - causing laminitis
PUPD
Weight loss - high cortisol, immunosuppressed so high parasite burden
Docile
Sweat more (hyperhidrosis)
What is the best first line/in field test for PPID?
Resting plasma ACTH concentration
(not ACTH stim - this is test in dogs)
What tube do you use to collect blood for a resting plasma ACTH concentration test?
In a cold plastic EDTA tube, centrifuge for plasma
What is the most sensitive test for PPID (done in hospital usually)?
TRH stimulation test
How do you do a TRH stimulation test for PPID?
Take bloods - for baseline ACTH
Inject TRH
Take bloods 10 and 30 mins after
What findings will you get on a TRH stimulation test if the horse has PPID?
Massive response of ACTH to the TRH if positive
How do you treat PPID medically?
Pergolide - dopamine agonist, calms down pituitary (the purge for PPID)
With management eg. farriery, clipping, parasite control
What causes hypothyroidism in foals?
Too much/too little iodine intake by mare during gestation
What are the signs/tests of hypothyroidism in foals?
Thyroid enlargement - due to excess TSH secretion from low TH negative feedback
Measure T4 levels
TSH/TRH stimulation test
What is the prognosis for hypothyroid foals?
Very poor - cant be reversed as happened during development of foetus
What type of thyroid tumours do horses get?
Adenoma - unilateral enlargement but usually no thyroid dysfunction
What is a granulosa-theca cell tumour?
Benign tumour causing enlarged ovary, poor fertility
Stallion like behaviour (but not always)
How do you diagnose granulosa-theca cell tumour?
Rectal - enlarged ovary
Anti-Mullerian hormone test - elevated testosterone
How do you treat granulosa-theca cell tumour?
Surgical removal - standing laparoscopic assisted or laparotomy
What are the 3 most common metabolic diseases of horses?
Equine metabolic syndrome
Hyperlipaemia
Hypocalcaemia
What are the 3 main features of equine metabolic syndrome (EMS)?
Obesity or regional adiposity
Insulin dysregulation/resistance
Subclinical/clinical laminitis
What is the difference between EMS insulin dysregulation/resistance and type 2 diabetes mellitus?
EMS has COMPENSATED insulin resistance - high blood insulin but normal glucose levels
Type 2 diabetes - uncompensated, high insulin and glucose
What directly causes laminitis in EMS?
The hyperinsulinaemia directly causes laminitis - too high insulin
What breeds of horse are predisposed to EMS?
Hardy breeds - can eat less and survive as high insulin means can mobilise energy stores more easily
What two factors increase EMS?
Obesity - increases insulin resistance
Lack of exercise - exercise promotes insulin sensitivity
What is the best test for EMS?
Oral glucose tolerance test -
Starve overnight
Take resting glucose/insulin
Feed glucose in breakfast
Take insulin/glucose at 2-3 hours
If has EMS then will get hyperinsulinaemia and normoglycaemia
How do you manage EMS?
Low carb, no concentrate diet
If thin then give calories in oil
No grass - grass muzzle
Exercise
Weight loss
Metformin - increases insulin sensitivity if diet isnt working
What causes hyperlipaemia?
Stress, not eating - negative energy balance
Mobilisation of fats/lipolysis too quickly for liver to keep up - VLDLs in circulation
Causes liver/kidney failure, fat embolism and death
What is the difference between hyperlipaemia and hyperlipidaemia?
Hyperlipidaemia - early stage of the same disease, cant see the fat in the blood yet though
How do horses mobilise energy due to negative energy balance?
Fatty acid oxidation
Dont make ketone bodies like cows do
What types of horse are at risk of hyperlipaemia?
Obesity
Ponies
In foal
Donkeys!
Insulin resistance - EMS
What enzyme is rate limited so gets overwhelmed during hyperlipaemia?
Endothelial lipoprotein lipase - hormone that puts VLDLs back into fat
How do you test for hyperlipaemia?
Blood triglyceride level
How do you treat hyperlipaemia?
Increase energy intake/balance - glucose infusion
Treat hepatic disease
Treat stress/concurrent disease
Inhibit fat mobilisation
Increase triglyceride uptake into peripheral tissues
What is the prognosis of hyperlipaemia?
60-100% mortality
0-40% chance of survival
What are the clinical signs of hypocalcaemia due to?
Increased neuromuscular excitability
What conditions/signs are caused by hypocalcaemia?
Synchronous diaphragmatic flutter - thumps
Hypocalcaemic tetany
Seizures
Ilius
Retained placenta
What is thumps?
Diaphragmatic contractions synchronous with the heartbeat due to low calcium
After prolonged exercise
How do you treat hypocalcaemia?
Max 2mg/kg/hr calcium gluconate solution - not too fast as causes CV complications
