Adrenal gland Flashcards
What are the two parts to the adrenal gland and what do they secrete?
Outer cortex - subdivided into 3 layers, each producing different adrenal steroids
Inner medulla - catecholamines
What are the 3 concentric zones to the outer cortex? What does each secrete?
All secrete steroid hormones = derived from cholesterol = fat soluble
- Outermost = Zona glomerulosa - mineralocorticoids
- Middle = Zona fasciculata - glucocorticoids (cortisol)
- Inner = Zona reticularis - androgen precursors
Where are they adrenal glands found?
Above the kidney
What regulates synthesis of glucocorticoids? Where is this produced?
ACTH (adrenocorticotropic hormone)
From anterior pituitary gland
What regulates ACTH?
CRH - corticotropin releasing hormone
What effect does rising blood glucocorticoid concentration have on other hormones?
Inhibits CRH and ACTH
What stimulates CRF (corticotropin releasing hormone ) release and activation of the HPA axis?
Stress
E.g. physiological factors, excess heat/injury, infections
The HPA axis is triggered by stress. Describe the HPA axis
Hypothalamus produces CRH
Triggers pituitary to produce ACTH
Triggers adrenal gland to produce cortisol
What is the precursor of glucocorticoids?
Cholesterol
Converted to pregnenoline, regulated by ACTH
What are the main effects of glucocoticoids on glucose/glycogen?
Decrease uptake and use of glucose
Increase glycogen storage
Stimulate gluconeogenesis in liver- results in hyperglycaemia
What are abnormalities of the adrenal gland?
Hyperadrenocortism - Overproduction of adrenal cortex hormones = Cushing’s
Hypoadrenocortism - Addison’s disease
What tests can be used to diagnose abnormalities of adrenal function?
Baseline cortisol and aldosterone
Endogenous ACTH
How does the anterior pituitary lead to aldosterone production?
Anterior pituitary produces ACTH
Stimulates the adrenal cortex to make aldosterone
Clinical signs of Hyperadrenocortocism in dog and what do we call this disease?
Called Crushings
- Increases gluconeogenesis = HYPERglycaemic –
- Increase protein catabolism = tissue wasting, muscle weakness and a pot belly (redistribution of fats in the body which contributes to pot belly)
- Inhibits growth means hair loss, bilateral non itchy hair loss/ thinning
- PUPD
Diabetic animals that present with PUPD is due to X. Is this the same or different with hyperadrenocorticism in a dog?
CRUSHINGS
Diabetic dog PUPD is due to glycosuria
Hyperadrenocortism is due to cortisol interfering with antidiuretic hormone resulting in poly uria and secondary polydipsia
What is hyPOadrenocorticism?
Addisons disease
When dogs can’t produce enough glucocorticoids (cortisol) and/ or mineralocorticoids (aldosterone) from cortex of adrenal gland
What are the effects of aldosterone on the body adn where is it released frm?
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.
Deficiency in aldosterone results in what?
hyperkalaemia and hyponatraemia
Increase in K and decrease in Na in blood, best seen by ratio
Na:K ratio below than 27:1
Clinical signs of aldosterone deficiency/ hypoadrenocorticism/ addisons
- Too much potassium (Hyperkalaemia) cardiac arrhythmias including bradycardia
- Low sodium (Hyponatraemia) Hypovolaemia and circulatory collapse – low blood pressure and heart rate
What can be used to treat Hyperadrenocorticism?
CUSHINGS
Dopamine receptor agonist (horse)
Mineralocorticoid receptor antagonist (dog)
Dopamine receptor agonist, how it works? what to treat?
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
Adrenal steroid synthesis inhibitors. How it works and what to treat?
Treats CRUSHINGS/ Hyper adrenocorticism
Competitive inhibitor of 3-B hydroxysteroid dehydrogenase (converts pregnenolone to progesterone)
Therefore inhibits corticosteroid synthesis
What can be used to treat HYPOadrenocorticism?
Mineralocorticoid receptor agonist (dog)
Glucocorticoid receptor agonists (dog)
MOA Glucocorticoid receptor agonists
For HYPOadrenocorticism
Stimulates glucocorticoid receptors, causing synthesis of corticosteroids
