Adrenal gland

Question 1

What are the two parts to the adrenal gland and what do they secrete?

Answer 1

Outer cortex - subdivided into 3 layers, each producing different adrenal steroids
Inner medulla - catecholamines

Question 2

What are the 3 concentric zones to the outer cortex? What does each secrete?

Answer 2

All secrete steroid hormones = derived from cholesterol = fat soluble

1. Outermost = Zona glomerulosa - mineralocorticoids
2. Middle = Zona fasciculata - glucocorticoids (cortisol)
3. Inner = Zona reticularis - androgen precursors

Question 3

Where are they adrenal glands found?

Answer 3

Above the kidney

Question 4

What regulates synthesis of glucocorticoids? Where is this produced?

Answer 4

ACTH (adrenocorticotropic hormone)

From anterior pituitary gland

Question 5

What regulates ACTH?

Answer 5

CRH - corticotropin releasing hormone

Question 6

What effect does rising blood glucocorticoid concentration have on other hormones?

Answer 6

Inhibits CRH and ACTH

Question 7

What stimulates CRF (corticotropin releasing hormone ) release and activation of the HPA axis?

Answer 7

Stress

E.g. physiological factors, excess heat/injury, infections

Question 8

The HPA axis is triggered by stress. Describe the HPA axis

Answer 8

Hypothalamus produces CRH
Triggers pituitary to produce ACTH
Triggers adrenal gland to produce cortisol

Question 9

What is the precursor of glucocorticoids?

Answer 9

Cholesterol

Converted to pregnenoline, regulated by ACTH

Question 10

What are the main effects of glucocoticoids on glucose/glycogen?

Answer 10

Decrease uptake and use of glucose
Increase glycogen storage
Stimulate gluconeogenesis in liver- results in hyperglycaemia

Question 11

What are abnormalities of the adrenal gland?

Answer 11

Hyperadrenocortism - Overproduction of adrenal cortex hormones = Cushing’s
Hypoadrenocortism - Addison’s disease

Question 12

What tests can be used to diagnose abnormalities of adrenal function?

Answer 12

Baseline cortisol and aldosterone

Endogenous ACTH

Question 13

How does the anterior pituitary lead to aldosterone production?

Answer 13

Anterior pituitary produces ACTH

Stimulates the adrenal cortex to make aldosterone

Question 14

Clinical signs of Hyperadrenocortocism in dog and what do we call this disease?

Answer 14

Called Crushings

1. Increases gluconeogenesis = HYPERglycaemic –
2. Increase protein catabolism = tissue wasting, muscle weakness and a pot belly (redistribution of fats in the body which contributes to pot belly)
3. Inhibits growth means hair loss, bilateral non itchy hair loss/ thinning
4. PUPD

Question 15

Diabetic animals that present with PUPD is due to X. Is this the same or different with hyperadrenocorticism in a dog?

Answer 15

CRUSHINGS

Diabetic dog PUPD is due to glycosuria
Hyperadrenocortism is due to cortisol interfering with antidiuretic hormone resulting in poly uria and secondary polydipsia

Question 16

What is hyPOadrenocorticism?

Answer 16

Addisons disease
When dogs can’t produce enough glucocorticoids (cortisol) and/ or mineralocorticoids (aldosterone) from cortex of adrenal gland

Question 17

What are the effects of aldosterone on the body adn where is it released frm?

Answer 17

Released from zonaglomerulosa (outer layer cortex of adrenal gland)
• Aldosterone binds to receptors in the principal cells on the collecting ducts of the nephron. It promotes the secretion of potassium and the reabsorption of sodium.

Question 18

Deficiency in aldosterone results in what?

Answer 18

hyperkalaemia and hyponatraemia

Increase in K and decrease in Na in blood, best seen by ratio

Na:K ratio below than 27:1

Question 19

Clinical signs of aldosterone deficiency/ hypoadrenocorticism/ addisons

Answer 19

• Too much potassium (Hyperkalaemia) cardiac arrhythmias including bradycardia
• Low sodium (Hyponatraemia)  Hypovolaemia and circulatory collapse – low blood pressure and heart rate

Question 20

What can be used to treat Hyperadrenocorticism?

Answer 20

CUSHINGS

Dopamine receptor agonist (horse)
Mineralocorticoid receptor antagonist (dog)

Question 21

Dopamine receptor agonist, how it works? what to treat?

Answer 21

Treat: HYPERadrenocortism
Cushings = loss of dopaminergic inhibition to the intermediate lobe of the pituitary
Works by acting on dopamine receptors so sorts out this problem

ONLY HORSES

Question 22

Adrenal steroid synthesis inhibitors. How it works and what to treat?

Answer 22

Treats CRUSHINGS/ Hyper adrenocorticism

Competitive inhibitor of 3-B hydroxysteroid dehydrogenase (converts pregnenolone to progesterone)
Therefore inhibits corticosteroid synthesis

Question 23

What can be used to treat HYPOadrenocorticism?

Answer 23

Mineralocorticoid receptor agonist (dog)

Glucocorticoid receptor agonists (dog)

Question 24

MOA Glucocorticoid receptor agonists

Answer 24

For HYPOadrenocorticism

Stimulates glucocorticoid receptors, causing synthesis of corticosteroids