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3. Equine 2 > Endocrine Disorders in Horses > Flashcards

Endocrine Disorders in Horses Flashcards

1
Q

most important 3 endocrine disorders in horses

A
  • Equine Metabolic Syndrome
  • Pituitary Pars Intermedia Dysfunction
  • Thyroid Diseases
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2
Q

Equine Metabolic Syndrome (EMS)
- who is affected? age and breeds? etiology?

A
  • Usually affects mature horses
    > any adult horse can get this!
    <><>
    Breed predisposition:
  • Pony breeds
  • Morgan
  • Icelandic
  • Miniature Horses
  • Donkeys
    <><>
  • Genetic predisposition: suspected but not confirmed
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3
Q

Equine Metabolic Syndrome (EMS)
- clinical signs

A

Obesity - general or regional adiposity
* Cresty neck
* Tail head
* Supraorbital fat pads
* Mammary, sheath
<><><>
* “Easy keepers”
* Poor fertility
* Clinical or subclinical laminitis

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4
Q

Equine Metabolic Syndrome (EMS)
* Pathophysiology vs normal

A

Normal insluin response after a meal:
- increased glucose in the SI
> relesase of incretin hormones
> increase insulin secretion
> clearance of insulin
<><><><>
Hyperinsulinemia
- increased glucose in the SI
> VERY increased release of incretin hormones
> VERY increased insulin secretion
> VERY decreased clearance of insulin
<><><><>
Hyperinsulinemia and laminitis (not fully understood yet)
- hyperinsulinemia > ectivation of IGF=1 receptors in the blood vessels > vascular dysfunction > hyperinsulinemia-associated laminitis

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5
Q

Equine Metabolic Syndrome (EMS)
* The “triad”

A
  • hyperglycemia (eg. after eating, normal)
    > stimulates beta cell secretion
  • hyperinsulnemia
    > compensatory pancreatic secretion, reduced insulin clearance
  • insulin resistance
    > reduced suppression of lipolysis and hepatic VLDL synthesis
  • hypertriglyceridemia
    <><>
  • insulin resistance also impairs insulin signalling, stimulates lipogenesis
    > Hyperinsulinemia
  • also impairs glucose uptage, reduces suppesttion of gluconeogenesis
    > hyperglycemia
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6
Q

Equine Metabolic Syndrome (EMS)
* Diagnosis

A

clinical signs and tests:
* Obesity
* Laminitis
* Hyperinsulinemia
> single measurement - basal inslulin
> dynamic test - oral glucose tolerance test, or combined glucose-insulin tolerance test

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7
Q

Equine Metabolic Syndrome (EMS)
- treatment and management

A
  • DIET > minimize carbohydrates and sugar
  • Turn out/exercise
  • Laminitis management
    <><><><>
  • Metformin
  • Levothyroxine
  • Sodium-glucose co-transporter 2 (SGLT2)
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8
Q

Pituitary Pars Intermedia Dysfunction (PPID)
- who is affected?
- clinical signs?

A
  • Usually affects horses older than 10-years-old
    <><>
    Clinical signs:
  • Hypertrichosis (hirsutism)
  • Poor hair coat
  • Hyperhidrosis
  • Laminitis
  • Lethargy
  • Recurrent infections
  • Weight loss/muscle wasting
  • Pendulous abdomen/fat redistribution
  • PU/PD
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9
Q

Pituitary Pars Intermedia Dysfunction (PPID)
- pathophysiology, normal vs PPID

A

HEALTHY:
- dopamine from hypothalamic neurons inhibits cells in the pituitary pars intermediata
- this limits release of ACTH and related peptides from pars intermediata cells into the blood stream
<><><><>
PPID:
- hypothalamic dopaminergic neurons undergo oxidative stress and degenerate
- results in loss of inhibition of the pars intermediata, leading to hyperplasia or adenoma formation
- pars intermedia release of ACTH and related peptides increases (eg. POMC)

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10
Q

Pituitary Pars Intermedia Dysfunction (PPID)
* Diagnosis:

A
  • Basal tests > Plasma ACTH: changes based on month, but overall if ACTH is very high, that supports a diagnosis
  • Dynamic tests > TRH stimulation test: stimulates ACTH to be released, PPID horses will have a larger increase that takes longer to go down
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11
Q

Pituitary Pars Intermedia Dysfunction (PPID)
* Treatment:

A
  • Pergolide (dopamine D2 receptor agonist)
  • Good quality feed + geriatric care
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12
Q

EMS and PPID connection?

A

Horses can have EMS and PPID at the same time!

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13
Q

Thyroid Diseases in horses - what do we see

A
  • Congenital hypothyroidism
  • Hypothyroidism in adult horses
  • Thyroid tumors
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14
Q

Congenital hypothyroidism
- what will our gland look like?
- other things we might see in these foals?

A
  • Thyroid gland hyperplasia!
    <><>
  • Goiter > inconsistent finding
    <><>
  • Prolonged gestation
  • Congenital musculoskeletal abnormalities
    > Flexural deformities
    > Incomplete ossification of cuboidal bones
    > Mandibular prognathy
    > Domed forehead
  • ie. signs of dysmaturity in a mare that is overdue
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15
Q

Congenital hypothyroidism
risk factors?

A
  • Might be associated with excess iodine consumption during pregnancy or not
  • Risk factors:
  • Lack of mineral supplementation during pregnancy
  • Grazing irrigated pasture
  • Eating immature cereal crop
  • Eating forage that contains nitrate
    <><><>
    Higher prevalence in Western Canada!
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16
Q

Thyroid Diseases
* Things to remember:
> neonatal foals thyroid hormone levels vs adults
> premature and septic foal levels?

A
  • Normal neonatal foals have thyroid hormones concentration 10 times higher than adult horses.
  • Premature foals and septic foals have significantly lower thyroid hormones concentration than normal foals.
17
Q

Hypothyroidism in adult horses
- dx?

A

RARE
Diagnosis: TRH stimulation test
* Currently, there are no commercially available tests for equine TSH
<><>
- blood thyroid hormone concentration alone should not be used to diagnose hypothyroidism in horses and are not a sufficient reason to begin replacement therapy

18
Q

Thyroid tumors - what are thyroid levels?
- best way to evaluate gland?
- hyperplasia = tumor?

A
  • tT3 and tT4 are 2-3 times higher than normal
  • ultrasound is the best way to evaluate an enlarged thyroid gland. Tumors may be solid or have a characteristic cystic appearance. BIOPSY OF THE GLAND IS NOT RECOMMENDED as the thyroid is an extremely vascular organ that bleeds profusely and percutaneous biopsy samples can be non-diagnostic.
    <><>
    Thyroid Hyperplasia ≠ Thyroid Tumor
    > thyroid hyperplasia is much more common

3. Equine 2 (16 decks)

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