Endocrine Disease - Equine Flashcards
What is the pathogenesis of hyperlipidemia?
negative energy balance
- triggers excessive mobilization of fatty acids from adipose tissue
- increased hepatic triglyceride synthesis and secretion of low density lipoproteins
What is hyperlipidemia?
What is hyperlipema?
hyperlipidemia - increased amount of all lipids and serum triglycerides (TG < 500 with clear plasma)
hyperlipemia - serum TG > 500 with cloudy serum
What are the risk factors for hyperlipidemia?
- ponies, miniature horses, donkeys
- obesity
- stress
- pregnancy
Describe the actions of the hormones involved in fat mobilization
lipoprotein lipase - activated by insulin, favors TG accumulation in adipose tissue
hormone sensitive lipase - expressed in adipose tissue, mobilizes stored fats
- inhibited by insulin
What are the 3 components of equine metabolic syndrome?
- increased adiposity (fat depositions)
- hyperinsulinemia
- insulin resistance
Which breeds are predisposed to equine metabolic syndrome?
ponies and Morgans
What is the biochemical cause of hyperlipemia?
overproduction of triglyceride
What are the complications associated with hyperlipidemia?
- hepatic failure
- renal failure
- death
What are the possible clinical presentations of equine metabolic syndrome?
- generalized obesity
- regional adiopsity
- laminitis
What is compensatory insulin resistance?
production of higher levels of of insulin, trying to overcome the resistance
- will be hyperinsulinemic
What is non-compensatory insulin resistance?
pancreatic insufficiency develops due to beta cell exhaustion
How is equine metabolic syndrome diagnosed?
- cresty neck
- fasting insulin levels
- insulin tolerance test
- oral sugar test
- combined glucose insulin test
Describe the insulin tolerance test
- insulin is administered and glucose concentration is measured over time
- normal if the concentration of glucose decreases by 50% within 30 minutes
Describe the Oral Sugar test
- fast the horse overnight
- administer corn syrup orally
- collect blood at 60 and 90 minutes
- measure insulin concentration
(> 60 at either time indicates post-prandial hyperinsulinemia)
Describe the combined glucose insulin test
- collect baseline blood sample, then IV infusion of dextrose followed by insulin
- if insulin resistant: BG concentrations remaining above baseline for > 45 minutes
- stress can alter results
What is the treatment for equine metabolic syndrome?
- increase activity and weight reduction
- limit sugars and carbs
- restrict pasture access
- Levothyroxine sodium, Metformin, Metaborol
What are the 3 types of hypothyroidism?
primary - iodine deficiency or excess
secondary - pituitary or hypothalamic dysfunction
tertiary - defect of hormone use at the periphery
What are the clinical signs associated with hypothyroidism?
- weight loss
- decrease in temp, HR, and CO
- increased sensitivity to cold
- lethargy, limb edema, decreased appetite
How is hypothyroidism diagnosed?
- baseline T3-T4
- T4 radioimmunoassay (most reliable)
- TRH or TSH stimulation test
How is hypothyroidism treated?
Levothyroxine supplementation
What is melanocyte stimulating hormone?
What are its functions?
- a primary product of POMC cleavage
- role in metabolism and obesity
- anti-inflammatory hormone
- reduces neutrophilic oxidative burst, chemotaxis, and adhesion
- antipyretic
What is the function of ACTH?
stimulates the adrenal glands to produce large amounts of cortisol
What are the functions of cortisol?
- stimulates gluconeogenesis
- activates anti-stress and anti-inflammatory pathways
- counteracts insulin
- diuretic, increases GFR, Na retention, and K secretion
What is the pathophysiology of Equine Pituitary pars Intermedia Dysfunction?
- a neurogenerative disease with loss of dopaminergic inhibitory input to the melanotropes of the pars intermedia
- hyperplasia of the pars intermedia
- slow progressive disease
What are the signs associated with PPID?
- hirsutism
- behavioral abnormalities
- muscle atrophy (epaxial and gluteal)
- abnormal fat distribution
- PU/PD
- hyperhidrosis
- infertiliy
- neurologic disease
- laminitis
How is PPID diagnosed?
- plasma ACTH concentration
- Dexmethasone suppression test
- MSH plasma concentration
- Domperidone stimulation test
- ACTH stimulation test
- TRH stimulation test
- combined DST and TRH stimulation test
What are the treatments for PPID?
- Peroglide (dopamine agonist)
- Cyproheptadine
- Trilostane
