Endocrinopathic laminitis

Question 1

What three things occur during laminitis?

Answer 1

1. elongation of secondary epidermal laminae- primarily due to stretching small increase in cell proliferation
2. increased mitosis
3. increased apoptosis

Question 2

What is the link between IGF-1 and laminitis?

Answer 2

• lamellar epithelial cells have IGF-1 receptors
• IGF-1 receptors are stimulated by high concentrations of insulin
• therefore hyperinsulinaemia may abnormally stimulate lamellar epithelial growth
• elongate SEL’s therefore weakening lamellar cohesion

Question 3

What stimulates corticotroph secretion?

Answer 3

It is stimulated by corticotroph releasing factor from the hypothalamus

Question 4

What controls the secretion of melanotrophs?

Answer 4

• melanotrophs secrete autonomously
• controlled by inhibitory dopaminergic neurones from the hypothalamus

Question 5

What are the clinical features of PPID

Answer 5

• associated with aging
• associated with laminitis
• excessive drinking and urination
• muscle catabolism

Question 6

What three conditions are associated with insulin dysregulation?

Answer 6

• Equine metabolic syndrome
• PPID/ Equine Cushings
• Exogenous glucocorticoid administration

Question 7

What three risk factors relate to endocrinopathic laminitis?

Answer 7

• Obesity
• Cardiovascular changes
• Adipose dysregulation

Question 8

What would you notice in the tests for Equine Metabolic syndrome?

Answer 8

• High Insulin
• High Triglyceride
• High leptin in adipokines
• Adiponectin is low

Question 9

What peptide do both Corticotrophs and Melanotrophs synthesise?

Answer 9

241-amino-acid peptide propiolipomelanocortin/ POMC

Question 10

What three ways is POMC cleaved?

Answer 10

◦ Prohormone convertase 1/3 (PC 1/3)
◦ Prohormone convertase 2 (PC2)
◦ Carboxypeptidase E (CPE)

Question 11

What is corticotroph secretion stimulated by?

Answer 11

Cortciotroph Releasing factor from the hypothalamus and therefore carried to the pituitary via the blood

Question 12

How are melanotrophs secreted?

Answer 12

they secrete autonomously and are controlled by inhibitory dopaminergic neurones from the hypothalamus

Question 13

What is the primary causal event in development of PPID?

Answer 13

Oxidative damage to the inhibitory dopaminergic neurones

Question 14

What are the Clinical Defining features of PPID?

Answer 14

• Aging
• Susceptability to laminitis
• Abnormal hair growth
• excessive drinking/ urination
• susceptability to infections
• muscle catabolism

Question 15

What are the metabolic defining features of PPID?

Answer 15

• Increased production of POMC-derived peptides
• insulin dysregulation
• insulin resistance
• hyperinsulinaemia
• hypertriglycerideamia

Question 16

Name three POMC peptides that would be high on a PPID lab test

Answer 16

• ACTH
• a-MSH
• B-endorphin

Question 17

What happens between insulin and the MAP kinase pathway?

Answer 17

Insulin resistance affects the PI3 kinase pathway, so insulin overstimulates the MAP kinase pathway therefore cellular growth/ differentiation occurs

Question 18

What are the equine metabolic syndrome risk factors for endocrinopathic laminitis?

Answer 18

• Insulin dysregulation
• Obesity
• Cardiovascular changes
• Adipose dysregulation

Question 19

What are the clinical features of equine metabolci syndrome?

Answer 19

• Susceptability to laminitis
• Obesity/ Generalised and/or regional

Question 20

What are the metabolci features of equine metabolic syndrome?

Answer 20

• Hyperinsulinaemia
• insulin resiatnce
• hypertriglyceridaemia

Question 21

What most likely causes the metabolic features of Equine metabolic syndrome?

Answer 21

• Genetic factors
• obesity
• inactivity
• diet high in non-structural carbohydrates

Question 22

What are the predominant cell types in Equine anterior pituitary anatomy?

Answer 22

• Corticotrophs
• Melanotropes

they both synthesise propiolipomelanocortin POMC

Question 23

How are melanotrophs secreted?

Answer 23

They are secreted autonomously and are controlled by inhibitory dopaminergic neurones from the hypothalamus

Question 24

What is the primary causal event in development of PPID?

Answer 24

oxidative damage to inhibitory dopaminergic neurones
- releases the pars intermedia from inhibition
* causes increased secretion

Question 25

What are the grades of PPID?

Answer 25

1. normal- normal 2. mild hypertrophy- normal age effects 3. marked hypertrophy- mild PPID 4. microadenoma- moderate PPID 5. macroadenoma- marked PPID