AdrenaL Gland

Question 1

Where are the adrenal Glands located?

Answer 1

Situated superior pole of the kidney in the retroperitoneal space.

Question 2

What 2 separate areas make up the adrenal gland and what do they do?

Answer 2

1. Adrenal medulla - secretes catecholamines, epinephrine, norepinephrine and dopamine.
2. Adrenal cortex - secretes 3 classes of steroid hormones:
   - Mineralocorticoids e.g. aldosterone(essential) involved in regulation of Na and K
   - Glucocorticoids e.g cortisol(essential) involved in maintaining plasma glucose
   - sex steroids.

Question 3

The cortex surrounds the medulla - What are the 3 zones of cortex and what hormones do they produce?

Answer 3

Zona glomerulosa (bottom above capsule) - aldosterone
Zona fasciculata ( middle) - glucocorticoids 
Zona reticularis (top layer) - sex hormones

Question 4

What does a defect in 21-hydroxylase a common cause of?

Answer 4

Congenital adrenal hyperplasia resulting in deficiency of aldosterone and cortisol and associated disruption of salt and glucose balance.

Question 5

What is cortisol?

What does it do?

Answer 5

Glucocorticoid hormone 95% of plasma cortisol bound to carrier protein - CBG.
All nucleated cells have cytoplasmic glucocorticoid receptors.
- Hormone receptor complex binds to DNA alter gene expression, transcription and translation.

Question 6

Why is cortisol essential for life?

Answer 6

Removal of adrenal glands in animals results in death in a few weeks.
Loss of cortisol means animals cannot deal with stress, particularly maintaining blood glucose levels.
Crucial in helping to protect brain from hypoglycaemia.
Permissive action on glucagon.

Question 7

What are the actions of cortisol on glucose metabolism?

Answer 7

1. Stimulates formation of GLUOCNEOGENIC enzymes in liver enhancing GLUCONEOGENESIS.
2. Proteolysis: Stimulates breakdown of muscle protein to provide gluconeogenic substrates for liver.
3. Lipolysis: Stimulates lipolysis in adipose tissue increasing [FFA] plasma alternative fuel supply.
4. Decreases insulin sensitivity of muscles and adipose tissue

Question 8

What are the non glucocorticoid actions of cortisol?

Answer 8

1. Neg affect on Ca balance - net Ca loss.
2. Impairment of mood and cognition
3. Permissive effects on norepinephrine - low levels of cortisol associated with hypotension.
4. Suppression of the immune system - cortisol reduces circulating lymphocyte count, reduces antibody formation.

Question 9

What are side effects of glucocortoid therapy?

Answer 9

Increased severity and frequency of infection

Loss of percutaneous fat stores - appearance of thinning skin - fragile

Question 10

What is Aldosterone?

What does it do?

Answer 10

Mineralocorticoid, acts on kidney to determine levels of minerals reabsorbed/excreted
- Increases reabsorption of Na and promotes excretion of K.

Question 11

What is the end effect of aldosterone release?

Answer 11

Increased aldosterone release stimulates Na retention and K depletion - increased BP.
Decreased leads to Na loss and increase in [K]plasma, resulting in diminished blood vol - decreased blood pressure

Question 12

What disorders happen with hyper secretion of cortisol?

Answer 12

Cushing syndrome

- hyper secretion is most commonly due to a tumour in adrenal cortex or pituitary gland.

Question 13

What disorders happen with hyposecretion of cortisol

Answer 13

Much less common
Addison’s disease
- due to autoimmune destruction of adrenal cortex

Question 14

What is the adrenal medulla?

Answer 14

Modified sympathetic ganglion - neuroendocrine role.
Preganglionic sympathetic fibres treminate on specialised postganglionic cells in adrenal - released directly into blood.

Question 15

What is a pheochromocytoma?

Answer 15

Rare neuroendocrine tumour found in adrenal medulla. Causing Increased HR - increased CO and Increased BP.