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Clinical Endocrine, Metabolic and Dermatology > Equine Endocrine and Metabolic Diseases > Flashcards

Equine Endocrine and Metabolic Diseases Flashcards

Adrenal, Thyroid and Parathyroid Diseases

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1
Q

What are the 3 main Adrenal diseases of horses?

A

1) Adrenal Insufficiency
2) Pheochromocytoma
3) Anhidrosis

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2
Q

What are the 2 main Thyroid gland diseases of horses?

A
  • Neonatal hypothyroidism

- Thyroid tumors

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3
Q

What are the 2 main Parathyroid gland diseases of horses?

A
  • Hyperparathyroidism

- Pseudohyperparathyroidism

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4
Q

What are the 2 main Pancreatic diseases of the horse?

A
  • Diabetes mellitus: rare

- Hypoglycemia: rare, but may occur due to pancreatic tumor

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5
Q

What are the causes of Adrenal Insufficiency in the horse?

A

Adrenal glands are known as the ‘shock’ organs in the horse, therefore causes include:

  • Endotoxemia
  • Colic
  • Chronic use of corticosteroids, or at higher doses

Both of which lead to hemorrhage and necrosis of the adrenals

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6
Q

What are the common risk factors associated with Adrenal Insufficiency?

A
  • Just off the track
  • Intensive training
  • Steroid use
  • Recent colic
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7
Q

What are the clinical signs associated with Adrenal Insufficiency?

A
  • Poor condition
  • Poor performance
  • Lethargy
  • Depression
  • Anorexia
  • Weight loss
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8
Q

What are the typical findings on serum biochemistry of a horse with Adrenal Insufficiency?

A
  • Hyponatremia
  • Hypochloremia
  • Hyperkalemia
  • Hypoglycemia
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9
Q

How can Adrenal Insufficiency be diagnosed in the horse?

A
  • ACTH gel 1 IU/kg given IM
    Serum cortisol levels taken pre- and 2-4hours post administration

note: normal horse will see a 2-3x increase in cortisol conc
note: a horse with Adrenal Insufficiency will see less than this

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10
Q

What is the treatment for Adrenal Insufficiency in the horse?

A
  • Rest and reduction of stress

- Long term corticosteroid administration should be weaned off

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11
Q

What is a Pheochromocytoma?

A

Functional adrenal medullary tumour, which causes an excess of catecholamine production from the adrenal medulla
- Catecholamines: Epinephrine, Norepinephrine and Dopamine

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12
Q

What are the clinical signs associated with Pheochromocytoma in the horse?

A
  • Usually present similar to acute colic
  • Increase HR
  • Increase RR
  • Dilated pupils
  • Sweating
  • Anxiety
  • Diarrhea
  • Muscle tremors
  • PU/PD
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13
Q

How can Pheochromocytoma be diagnosed in the horse?

A
  • Diagnostic imaging: limited access though
  • Hematology and biochemistry: non-specific
    Neutrophilia, lymphopenia: stress response
    Hemo-concentration: splenic contraction
    Hyperglycemia, uremia, hyper-kalemia

note: usually diagnosed on the table while the horse is undergoing colic surgery- since this is similar to how they present

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14
Q

What is the treatment of Pheochromocytoma in the horse?

A

Supportive Tx: address renal function with fluids
Medical Tx: not usually attempted
Surgical Tx: high risk of cardiac arrhythmias, rhabdomyolysis and excess bleeding

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15
Q

What is Anhidrosis?

A

The inability to sweat normally, which can lead to hyperthermia and heat exhaustion

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16
Q

A horse that came from a relatively cold climate to a warmer climate is more predisposed to _______

A

Anhidrosis within 1-3 months of arrival

This is thought to be due to sweat glands shrinking due to environmental stress or exercise

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17
Q

What are the clinical signs associated with Anhidrosis in the horse?

A
  • Poor stamina and exercise intolerance
  • Panting, distress and lethargy after exercise
  • Heat overload + collapse
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18
Q

How can Anhidrosis be diagnosed in the horse?

A
  • Usually clinical signs and a history of moving to a warm climate is enough
  • Intradermal injection of Beta2-agonists
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19
Q

What is the treatment/ management for Anhidrosis in the horse?

A
  • Move horse to a milder, less humid climate
  • Compete during the winter months only
  • Daily electrolyte supplementation
  • Provide a cool environment: fans or AC, shade
  • Body clipping
  • Hosing with cool, water after exercise
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20
Q

What can Neonatal Hypothyroidism be caused by?

A

Neonatal goiter due to:

  • Iodine deficiency in the diet of the mare
  • Excess nitrates in the diet of the mare
  • Ingestion of goitrogens by the dam: plant goitrogens will cross the equine placenta and interfere with iodine uptake in the gland
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21
Q

Where in the world is Neonatal Hypothyroidism most commonly reported?

A

Canada

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22
Q

What are the two presentations of a foal with Neonatal Hypothyroidism?

A

1) Foal is in hypo-metabolic state with low thyroid hormone concentration
2) Developmental lesions are found with normal thyroid hormone concentrations: this happened due to hormone deprivation during the critical period of development

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23
Q

What are the clinical signs associated with Neonatal Hypothyroidism?

A
  • Dysmature
  • In-coordiantion
  • Poor suckling reflex and unable to right itself: neurological presentation due to hypomyelination
  • Hypothermia and a low BMR
  • Tendon contracture/ rupture
  • Retarded bone development
  • Undershot jaw: parrot mouth
24
Q

How can Neonatal Hypothyroidism be diagnosed?

What is the prognosis of this disease?

A
  • Clinical signs + history of mares diet
  • TSH response test
  • Post-mortem

Prognosis: poor to guarded- don’t often make it as athletes.
However it has been seen of foals with only a goiter as a presenting problem to ‘grow out’ of it and perform normally

25
Q

Can adult horses get hypothyroidism?

A

Yes, but it is extremely rare and often over diagnosed

Typically what the horse (or pony) has is Equine Metabolic Syndrome

26
Q

How can Adult Hypothyroidism be diagnosed in the horse/ pony?

A
  • Low serum T3 and T4
  • TSH stimulation test

note: other factors can lead to low T3 and T4 including- Bute (pain-killer), Food deprivation, illness

27
Q

How can Adult Hypothyroidism be treated in the horse/ pony?

A
  • Thyroxine (T4) 20mcg/kg SID po

Used for the Tx of EMS too

28
Q

What are the two types of Hyperparathyroidism (aka Bran Disease)?

A
  • Primary: rare
  • Secondary: Nutritional, due to diets high in phosphorus or oxalates, which decrease the absorption of Ca in the GIT leading to Ca deficiency and PTH is secreted
29
Q

What are the clinical signs associated with Hyperparathyroidism (aka Bran Disease)?

A
  • Limb and Facial bone demineralization: loose teeth and a shifting intermittent lameness
  • Weanlings and Yearlings will fail to reach their expected height
  • Swollen facial bones, thickened jaw bones and difficulty chewing
  • Ruptured tendons and increased risk of fractures
  • Obstruction of nasal passages, which may cause a nice and/or a discharge
30
Q

How can Hyperparathyroidism (aka Bran Disease) be diagnosed?

A
  • Serum Ca and PO4: but are usually normal

- Urinary PO4 is typically elevated

31
Q

What is the treatment and prevention of Secondary Nutritional Hyperparathyroidism (aka Bran Disease)?

A
  • Tx: Dietary management
    note: it can take up to 12 months for re-mineralization of the bone

Prevention: Calcium supplementation if pastures are high in oxalates

32
Q

What are the most common causes of Diabetes Mellitus in the horse?

A

A rare condition in horses, but when it happens it is associated with Pancreatic destruction

  • Abscesses: Strep equi or Corynebacterium
  • Migrating Strongyles
33
Q

What are the most common Metabolic Diseases of the Horse?

A
  • Calcium: hyper and hypocalcemia
  • Copper and Selenium deficiencies
  • Hyperlipidosis/ Hyperlipemia
  • Hepatic Encephalopathy
34
Q

Why might Hypercalcemia be seen in a horse?

A

Paraneoplastic syndrome to:

  • Lymphoma
  • Gastric SCC
  • Mesothelioma

Vit D Toxicosos: eating too much Vit D, leading to increase absorption of Ca and P from the GIT and reabsorption from the kidneys

35
Q

How can Hypercalcemia be diagnosed in the horse?

A
  • Serum biochemistry: elevated Ca but normal PO4

- Pathological calcification of the soft tissues

36
Q

Why might Hypocalcemia be seen in the horse?

A
  • At peak lactation, especially in draft mares: ~10 days after foaling and due to inadequate feed supplementation
  • Prolonged Transportation
  • Endurance-type exercise
  • Severe colitis: e.g. blister beetle toxicosis
37
Q

What are the clinical signs associated with Hypocalcemia?

A
  • Tetany
  • Profuse sweating
  • Anxious appearance
  • Tachycardia
  • Cardiac arrhythmias
  • Synchronous Diaphragmatic Flutter: “Thumps”- diaphragm contracts with the heart beat
38
Q

What is the treatment for Hypocalcemia?

A
  • SLOW IV Calcium supplementation

note: must monitor the heart as you do this

39
Q

Why might Copper and Selenium deficiency occur in horses?

A
  • grazing copper and selenium deficient pastures
40
Q

What are the clinical signs associated Copper deficiency

A
  • Dull, brown hair coat

- Developmental Orthopedic Disease in foals

41
Q

What are the clinical signs associated Selenium deficiency?

A
  • Muscle disease: rhabdomyolysis or white muscle disease in foals born to Cu deficient mares
  • Poor growth and poor performance
  • Reproductive problems
  • Immune deficiency
42
Q

What is another name for Selenium toxicity, and why does it occur?

A

Selenium toxicity = Alkali disease

  • When horses ingest too much Selenium in the diet
43
Q

What are the clinical signs of Alkali disease in horses?

A
  • Fatigue
  • Loss of mane and tail hairs
  • Cracking of hoof and coronary band: sloughing of hooves

note: this is a life-threatning disease

44
Q

What is the difference between Hyperlipidemia and Hyperlipemia in the horse?

A

Hyperlipidemia: mild condition, clear serum, no hepatic dysfunction

Hyperlipemia: severe condition, with fat accumulation in the liver

45
Q

What are the predisposing risk factors to Hyperlipemia in horses, donkeys and ponies?

A
  • Obesity!
  • Certain equid breeds: miniature horses, pony breeds, donkeys- they are all relatively insulin resistant already, which worsens the disease
  • Negative Energy Balance:
    Malnutrition, starvation, anorexia or inappetance
    Stress (transport, weaning, or disease)
    Advanced pregnancy
    Enforced feed restriction
    Lactation
    Pituitary pars intermedia dysfunction (PPID)
46
Q

What are the clinical signs associated with Hyperlipemia?

A
  • Depression, weakness, in-coordination, anorexia, decreased gut motility

All of which can mask the underlying disease process that is more commonly the cause for the hyperlipemia in horses

47
Q

How can Hyperlipemia be diagnosed in horses?

A
  • Serum: may be white or yellow and opaque
  • Biochem: Increased hepatic enzymes, bile acids and bilirubin
    Increased TGIs and FFAs
    Azotemia
    Metabolic acidosis can develop in late stage
48
Q

What is the treatment for Hyperlipemia in horses?

A
  • Treat the primary disease
  • Nutrition: IV glucose to correct NEB +/- insulin
  • Fluid therapy: correct electrolyte and acid-base imbalance
49
Q

What is Hepatoencephalopathy?

A

Considered to be a clinical syndrome in horses, defined by an abnormal mental status, accompanied by severe hepatic insufficiency

50
Q

What is the most common presentation and causes of Hepatoencephalopathy in the horse?

A
  • Presentation: Diffuse acquired liver disease
  • Causes:
    Hepatic cirrhosis
    Hepatic necrosis
    Hepatic lipidosis –> Hyperlipemia
    Cholangiohepatitis
    Phytotoxic hepatitis
    Mycotoxicosis
51
Q

What is the most common cause of Hepatic cirrhosis in the horse?

A
  • Ingestion of pyrrolizidine alkaloid containing plants: ragweed or ragworth
    note: damage is irreversible to the liver
52
Q

How can liver cirrhosis be diagnosed in the horse?

A
  • Liver biopsy + histopathology: presence of megalocytes, portal fibrosis, biliary hyperplasia, necrosis
53
Q

What are the clinical signs associated with liver cirrhosis in horses?

A

1) Bizarre behaviour: depression, lethargy, excessive yawning, agitation, head pressing, ataxia, compulsive walking, circling, blindness, collapse and coma
2) Laryngeal dysfunction
3) Gastric Impaction: due to vagal nerve dysfunction

54
Q

What are the clinical signs associated with Hepatoencephalopathy in the horse?

A
  • Depression
  • Anorexia
  • Weight Loss
  • Jaundice
  • Photosensitization
  • Intravascular hemolysis
  • Pyrexia
55
Q

How can Hepatoencephalopathy be diagnosed in the horse?

A
  • Presence of encephalopathy
  • Evidence of impaired liver function: elevated serum bile acids and liver enzymes
  • U/S
  • Biopsy + Histopathology
  • Hyperammonemia
56
Q

What is the Treatment and Prognosis of Hepatoencephalopathy in the horse?

A

Supportive:

  • I/V dextrose + electrolytes
  • Monitor and correct acid-base balance

Dietary:
- Low-protein diet with a readily digestible CHO, high in branched-chain amino acids

Prognosis: poor to guarded

Clinical Endocrine, Metabolic and Dermatology (17 decks)

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