Equine Endocrinopathies Flashcards
what water intake would indicate equine polydipsia?
100 ml/kg/day
what does PPID stand for?
pituitary pars intermedia dysfunction
in what horses is PPID common?
aged
60% of over 20s had PM diagnosis of PPID
what should all horses with laminitis be tested for unless very young?
PPID
What is the proposed pathogenesis of PPID?
decrease in production of dopamine from the hypothalamus
this reduces inhibition of the pituitary
leading to enlargement of the pituitary gland and overproduction of pituitary hormones
why is there such a range of clinical signs with PPID?
there are differing levels of pituitary hormones at different times
what is the enlargement of the pituitary in PPID known as?
pituitary adenoma
what are the 2 types of pituitary adenoma?
micro
macro
what are the clinical signs of PPID?
variable! long curly coat laminitis PU/PD weight loss more docile neurological impairment hyperhidrosis change in fat distribution infertility skin disease periodontal disease no signs at all!
what is hyperhidrosis?
sweating excessively
what is the cause of the long curly coat in PPID?
unknown
what causes laminitis in PPID?
insulin resistance leading to high insulin levels which cause laminitis
what causes PUPD in PPID horses?
deceased secretion of vasopressin
what causes weight loss in PPID patients?
cortisol production
other associated disease
parasites
why are PPID patients often docile?
increased CSF B-endorphin
what causes neurological impairment of PPID cases?
compression from adenoma
how is PPID diagnosed?
gold standard test is postmortem only
based on clinical signs and signalment
why is PPID diagnosis difficult?
individual variation in hormone production
when is pars intermedia more active?
Autumn (august to december)
what is the first line diagnostic test used for PPID?
resting plasma ACTH concentration
what state should the horse be in when PPID sample is taken?
not stressed
how should resting ACTH blood samples be sent for analysis?
cold not frozen
send plasma
what ACTH reference range should be used when diagnosing PPID?
autumn
what test can be used to diagnose PPID if ACTH is borderline?
TRH stimulation test
how is a TRH stimulation test performed?
take baseline sample
inject TRH
second blood sample in 10 mins and then 30 mins after injection
what effect can administration of TRH have on the horse?
colic signs
sweaty
when are false PPID test positives likely?
autumn
what should happen if a horse has positive PPID test results?
start treatment
repeat tests in 4-6 weeks to check dose
when should tests be repeated in PPID patients?
annually
what should happen if a horse has a negative PPID test result but you have a strong clinical suspicion?
can start treatment anyway and assess clinical response however you will be unable to tell if you have the wrong dose or diagnosis if treatment won’t work
why is routine checking for PPID in aged horses useful?
can find those with no clinical signs
identify if at risk of laminitis
how is PPID treated?
management and medication
what is involved in management of PPID?
farriery clipping parasite control dental care feeding
when may management only of PPID be used?
if no laminitis
what medical treatment is used for PPID?
dopamine agonist - Pergolide tablets
what dose of Pergolide is given to PPID patients?
0.2-5 mg/horse per day (SID or split into BID)
what dose of Pergolide should you start with?
1 mg/horse
what is a side effect of Pergolide?
may go off food
what should happen if PPID is refractory to high doses?
split to BID (off label)
how should effect of Pergolide on PPID de monitored?
blood test and signs
adjust dose
reassess anually
what are the 3 areas of EMS?
obesity or regional adiposity
insulin dysregulation / resistance
subclinical or clinical laminitis
what is the effect of insulin dysregulation?
require abnormally high insulin to maintain glucose levels in the body
what are the conditions that lead to compensated insulin dysregulation?
EMS
PPID
what are the effects of compensated insulin dysregulation as seen in EMS?
high insulin levels to ensure normal glucose
many be seen at rest or only as response to feeding
what is a direct cause of laminitis?
hyperinsulinaemia
what is the role of genetics in EMS?
there is genetic predisposition for EMS in hardy breeds
what is the role of insulin?
facilitates breakdown of glucose and fat stores and stimulates hepatic gluconeogenesis
what is the survival benefit of insulin dysregulation in hardy breeds?
keeps glucose supply for vital tissues
are able to mobilise energy stores and prioritise vital tissues which aids survival
what is associated with insulin resistance / dysregulation?
obesity
why was insulin resistance protective?
would store fat over summer and become insulin resistant which would cause slower weight loss over the winter
the weight loss that did occur over the winter would then restore insulin sensitivity so they could deal with spring grass
why is EMS and insulin dysregulation an issue in modern horses?
no longer subject to seasonal weight loss
lack of exercise
chronic obesity and chronic laminitis are caused as remain insulin resistant all year round
what are the clinical signs of EMS?
obesity (BCS 7/9-9/9)
regional adiposity
subclinical or clinical laminitis
possible related disease (hyperlipaemia / lipoma)
where is regional adiposity seen in EMS?
cresty neck
tail head
preputial swelling
mammary glands
what conditions can cause insulin dysregulation?
EMS
PPID
both!
how can you test whether a horse has EMS or PPID?
history and signalment
test for both
is it possible to be lean and insulin resistant?
rare but possible
what is the issue with resting insulin and glucose tests for EMS?
many false negatives
what is the best first line test for EMS?
starved glucose tolerance
how is EMS glucose test performed?
starve
blood sample to test insulin and glucose levels
bolus of glucose / corn syrup
insulin and glucose measured at 30 mins or 2-3 hours
what is usually seen on a glucose test with a horse with EMS?
hyperinsulinaemia
normoglycaemia
how is EMS managed?
diet
medication can be used
exercise
weight loss
what can be changed about the diet to manage EMS?
low carbohydrate (so low sugar)
non concentrate
feed balancer to add vits and mins
no grass / restricted grass
what should lean horses with EMS be fed?
oils to ensure calories but no sugars
what feed could EMS patients have?
Happy Hoof or simular - designed for good doers
how can exercise help to manage EMS?
even a small amount can have a major effect on insulin sensitivity
how can weight loss be achieved?
feed 1/3 less than noraml
soak hay for >1 hr
use haynet with small holes to make food last longer
what is the minimum amount of forage that should be fed to any horse?
1.5 kg per 100kg
what drug can be used to aid EMS management in horses?
Metformin
what does metformin do in EMS patients?
no bioavailability but blocks SI carbohydrate absorption which decreases insulin resistance by weight loss
why is Metformin useful if it has no bioavailability?
if owners are struggling to get rid of the weight
helps with their mindset if horse is medicated
what is hyperlipaemia?
sudden release of fat into the blood
what is hyperlipaemia triggered by?
negative energy balance
stress leading to catecholamine and glucocorticoid release
what equines are at risk of hyperlipaemia?
obesity
native ponies
pregnancy
donkeys
what increases risk of hyperlipaemia?
excess stores of fatty acid
increased risk of insulin resistance
what is the pathogenesis of hyperlipaemia?
change in metabolism associated with sudden demand
the body needs energy so pumps out fat into the circulation
what is hyperlipaemia a disease of?
acute starvation
what can be caused by hyperlipaemia?
too much fat which the liver is unable to convert and there is not enough hormone to reduce levels
leads to hepatic lipidosis which worsens condition
lactescent blood
fat embolism
kidney failure
pancreatitis
what can be caused by hyperlipaemia which will worsen the condition?
liver failure
what impedes the development of hyperlipaemia?
insulin (normal function)
what can cause insulin resistance and so increase the risk of hyperlipaemia?
EMS
glucocorticoids
catecholamines
progesterone
when should you try and diagnose hyperlipaemia?
when patient only has hyperlipidaemia
what is hyperlipidaemia?
no gross fat present in the blood, precursor to hyperlipaemia
how can hyperlipaemia be prevented?
identify those at risk and try to prevent
what are the signs of hyperlipaemia?
depression
anorexia
ataxia
icterus
what are the 5 key area of hyperlipaemia treatment?
improve energy intake and balance
treat hepatic disease
eliminate stress and treat concurrent disease
inhibit fat metabolism from adipose tissue
increase triglyceride uptake by peripheral tissues
what can be done if a mare has a foal at foot and has hyperlipaemia?
wean foal to stop milk production as long as it isn’t too stressful
what sort of nutrition should be given to hyperlipaemia patients?
enteral (via stomach tube)
tempt to eat
what medical treatment can be used to treat hyperlipaemia?
glucose infusion
5% at 2ml/kg/hr
what is the purpose of glucose infusion in a hyperlipaemia patient?
stop fat being mobilised into blood
what should hyperlipaemia patients have monitored if receiving glucose infusion?
blood glucose hourly
what may need to be given to hyperlipaemia patients on glucose infusion?
insulin SC or infusion if glucose level too high
what is the prognosis of hyperlipaemia?
60-100% mortality
what is crucial in the prevention of hyperlipaemia?
education of clients
what can be done to avoid hyperlipaemia if the patient is at risk?
glucose infusion and insulin
