Endocrinology Flashcards
what does PPID stand for?
pituitary pars intermedia dysfunction
what are the three main parts of the pituitary gland?
pars distalis
pars intermedia
pars nervosa
what does the pars distalis produce?
prolactin, growth hormone, TSH, FSH, LH
what does the pars nervosa produce?
ADH and oxytocin
what does the pars intermedia produce?
ACTH and MSH
what is the pars intermedia receive information to release hormones?
neurotransmitter release from axons from the hypothalamus
what neurotransmitter inhibits release of ACTH and MSH from the pars intermedia?
dopamine
what neurotransmitter is responsible for PPID?
dopamine
why does the pars intermedia receive neurotransmitter from the hypothalamus unlike the pars distalis?
pars intermedia is poorly vascularised
how does the pars nervosa receive information regarding release/inhibiting hormone release?
direct axonal connection with hypothalamus
what hormones are released in excess from the pars intermedia in PPID cases?
beta-endorphin, alpha-MSH and ACTH
what is the first change within the body of a horse with PPID due to the decreased dopamine inhibition?
hyperplasia of the pars intermedia (due to increased hormone release)
what is MSH?
melanocyte stimulating hormone
what is alpha-MSH produced from in the pars intermedia?
ACTH (ACTH is processed further than in the other parts of the pituitary)
what is the only predisposing factor to PPID?
horses older than 15 (rarely less than 10 years old)
PPID is due to lack of dopamine inhibition on the pars intermedia, what type of disease does this mean PPID is?
neurodegenerative
what are the clinical signs of PPID?
hypertrichosis (delayed/abnormal shedding to a thick curly coat)
laminitis
weight loss/redistribution
wasted epaxial muscles and pot belly
bulging supraorbital fat
lethargy/reduced exercise tolerance
sweating
PUPD
what is hypertrichosis?
increased hair growth or delayed shedding
why is it important to confirm PPID diagnosis before treatment?
treatment will be lifelong
needed for monitoring horse (ACTH value)
determine if they have insulin dysregulation (laminitis risk)
how can you determine if a horse with PPID will develop laminitis?
evidence of insulin dysregulation
how is PPID diagnosed?
basal ACTH (don’t do when horse is stressed)
what type of tube is used to collect blood for a basal ACTH?
purple top tube (EDTA)
what time of year does basal ACTH test have the highest sensitivity?
autumn
what is the dynamic endocrine test for PPID?
ACTH response to TRH (not used very much in this country)
how commonly is the low dose dexamethasone test used for PPID used?
never in UK - invalid
what needs to be considered along with the basal ACTH test results for PPID?
horses age and clinical signs
what value should be used for the basal ACTH test if there are clear clinical signs and the horse is older than 15 years old?
lowest value (rule in the diagnosis) - low values have high sensitivity
what value should be used for the basal ACTH test if there is no clear clinical signs of PPID?
upper value (rule out diagnosis) - high values have high specificity
are induction of liver enzymes and stress leucograms seen in horses with PPID?
no (these should be investigated as a concurrent disease)
what is basal endocrine test used for PPID, that is not diagnostic?
glucocorticoid and insulin levels
what is the treatment for PPID?
pergolide (dopamine agonist)
how often should horses be monitored when being treated for PPID?
monthly in early stages to get the correct dose then every 3 months
what is used to monitor PPID treatment?
basal ACTH
how much can the dosage of pergolide be increased in PPID treatment?
5 times the original dose
should horses with PPID be put on a diet to prevent laminitis?
no - already have catabolism so don’t want to exacerbate this
how long are horses treated for PPID for?
lifelong
how is hypothyroidism tested for?
TRH stimulation of T3 and T4
what does EMS stand for?
equine metabolic syndrome
what does insulin do?
drives glucose into cells (decreases blood glucose levels)
if the target cells fail to respond to insulin, what is this called?
type 2 diabetes
what is EMS?
collection of risk factors for endocrinopathic laminitis
what is the most important factor of EMS that leads to endocrinopathic laminitis?
insulin dysregulation
what are the three main factors of EMS?
obesity
laminitis
insulin resistance
what are the typical features of a obese horse (predisposing to EMS)?
bulging supraorbital fat
enlarged crest
fat pads
what are the risk factors for EMS?
obesity
genetics
what does the insulin resistance have to be driven by to develop EMS and laminitis?
hyperinsulinaemia (by feeding high carbohydrate diet)
how is EMS diagnosed?
by diagnosing hyperinsulinaemia (using resting insulin)
what is the cut off point for unpasted insulin levels? (relating to EMS)
if its greater than 20 uIU/ml it has EMS
what is used as a dynamic test for EMS?
oral sugar/glucose test
how is the oral sugar/glucose dynamic test for EMS carried out?
fast horse for 6-12 hours then feed and sample blood 2 hours later
other than insulin resistance, what are the other clinical signs of EMS?
high blood pressure
hypertriglyceridaemia
mild basal cortisol elevation
what age horses can be effected by EMS?
any (younger than PPID)
how can EMS be managed?
reduce predisposing factor (obesity)
reduce hyperinsulinaemia
treat/manage laminitis
monitoring
is diet or exercise better for managing obesity and EMS?
exercise
what is done to the diet to manage obesity in EMS horses?
reduce caloric intake (give 1.5-2% body weight hay)
needs to be monitored and give protein, vitamins, minerals and salt supplements
how can hyperinsulinaemia be managed?
exercise
diet
drug therapy (thyro L)
nutraceuticals
