Endocrinology of Horses (PPID and EMS) Flashcards
Pathophysiology of PPID
Hypertrophy/hyperplasia of Pars intermedia (neoplasia) → Loss of dopaminergic control (oxidative stress and ↓ dopamine secretion and loss in inhibition) → Excess proopiolipomelanocortin (POMC, no neg feedback control) → ↑ ACTH and hyperadrenocorticism
What products are produced from Pars intermedia dysfunction
↑ cortisol
MSH and ↑ androgen from adrenal cortex: Hirtuism
ACTH and ↓ ADH: PU/PD
Compression of Pars nervosa: seizures
B-endorphins: lethargy
CS associated with ↑ cortisol?
Vasoconstriction
Protein depletion in dermis
Protein catabolism
Immunosuppression
IR (laminitis)
Resting plasma ACTH or a MSH (test for PPID)
Collect blood in EDTA tube
Resting ACTH >35 pg/ ml (not cortisol)
TRH stimulation test (test for PPID)*
Most sensitive for early cases
Corticotrophs abnormally stimulated by TRH (give IV)
If @ baseline >36 pg/ ml, >110 pg/mL @ 10 min (measures ACTH response)
Drugs for tx PPID
Pergolide mesylate
Capergoline
Cyproheptadine
Pergolide mesylate
Doperminergic agonist → compensates for less dopaminergic neurons and slows progression
Capergoline
Long-acting dopamine receptor agonist
Cyprohepatadine
Inhibits action of excitatory NT serotonin
Equine metabolic syndrome (EMS)
A cluster of risk factors that indicate that a horse is greater risk of developing endocrine laminitis
Pathophysiology of EMS
↓ in tissue response to circulating insulin which impairs insulin-mediated glucose → more insulin secreted from pancreas to compensate for lower tissue response → hyperinsulinemia → laminitis
Resting serum insulin (test for EMS)
Blood collected after short fasting period
Insulin > 20 uU/ mL, baseline elevated
False negs, poor sensitivity
Oral sugar test/ OST (test for EMS)
More sensitive
Syrup given → 60-90 min to collect blood → place in a red top/ purple top tube
Leptin baseline (test for EMS)
Hormone produced by adipocytes
↑ in EMS horses
EMS management
Limit calorie intake, eliminate pasture access and ↑ exercise
Forage with non-structural carbs <10% with soaking and balancer feeds
Avoid treats and high fat feeds
No exercise with laminitis
Drugs for EMS
Metformin
Levothyroxine
Velagliflorzin
Metformin
Horses with severe ID in combo with management changes
Direct effect on the enterocyte and decreases enteric glucose absorption and consequently the insulin response to an OGT in horses
Levothyroxine
With ↑adiposity to accelerate weight loss through ↑ metabolic rate
Velagliflorzin
Na-glucose linked transport-2 inhibitor
Reduces glucose resorption and promoting excretion
