Endocrinology 8 - The Adrenals and Corticosteroids

Question 1

Describe the circulation of the adrenal gland

Answer 1

• Left adrenal vein drains into the renal vein

- Right adrenal vein runs into the inferior vena cava

Question 2

Describe the anatomy of the adrenal gland.

Answer 2

• Adrenal medulla is in the middle
• Adrenal cortex is the outside. There are three layers, the zona glomerulosa, zonafasciculata and zona reticularis (starting from outside)
• Encased in a capsule

Question 3

Where are catecholamines made?

Answer 3

The adrenal medulla, in the chromaffin cells

Question 4

Where are corticosteroids made?

Answer 4

In the adrenal cortex

Question 5

What is a tributary vein?

Answer 5

A vein that enters into a larger vein

Question 6

Give some examples of catecholamines

Answer 6

• Adrenaline

- Noradrenaline (dopamine)

Question 7

Give some examples of corticosteroids

Answer 7

• Mineralocorticoids, such as aldosterone

- Glucocorticoids, such as cortisol

Question 8

Where is aldosterone made?

Answer 8

Zona glomerulosa

Question 9

Where is cortisol made (alongside some androgens and oestrogens)?

Answer 9

• Zona fasiculata makes cortisol

- Zona reticularis makes androgens

Question 10

What proportion of aldosterone is unbound, bound to CBG and bound to albumin?

Answer 10

40% unbound
15% bound to CBG
45% bound to albumin

Question 11

What proportion of cortisol is unbound, bound to CBG and bound to albumin?

Answer 11

10% unbound
80% bound to CBG
10% bound to albumin

Question 12

How much higher is the concentration of cortisol than that of aldosterone?

Answer 12

1000 fold difference, cortisol is highest at night

Question 13

Which receptors can cortisol bind to?

Answer 13

• Glucocorticoid receptors

- Aldosterone receptors

Question 14

Which receptors can aldosterone bind to?

Answer 14

Aldosterone receptors

Question 15

How does aldosterone regulate cortisol?

Answer 15

• Cortisol is converted to cortisone via 11bHSD2
• Cells that produce this enzyme are protected from cortisol, only aldosterone can bind to the receptors.
• This is present in the kidney and placenta (as cortisol would inhibit growth of the foetus)

Question 16

Describe how the renin-angiotensin-aldosterone system works.

Answer 16

• Sympathetic nerves, low blood pressure, and macular densa cells (low sodium ion concentration) increase renin production from granular cells.
• Renin increases sodium reabsorption and therefore water follows and blood pressure is reduced
• Renin acts on a angiotensin (liver and lungs) making aldosterone
• Aldosterone increases sodium channel expression

Question 17

Describe the mechanism of action of aldosterone

Answer 17

• Sodium channel expression in the distal tubule increases and the sodium potassium pump returns the sodium into the blood.
• Water follows as a result

Question 18

What is the optimal level of cortisol?

Answer 18

• All MR occupied and some GR
• High ratio
• Occurs in stress, and in the morning

Question 19

List the actions of cortisol in metabolism

Answer 19

• Increases glucogeneisis, making glucose readily available, and glycogenesis.
• Reduces blood flow and GLUT 4 expression in skeletal muscle
• Prevents storage of fatty acids in adipose

Question 20

List the actions of cortisol in memory

Answer 20

• Serotonin promotes memory formation.

- Cortisol increases serotonin production so in times of stress we learn and don’t repeat our mistakes

Question 21

List the supra-physiological actions of cortisol (when at higher levels than normal)

Answer 21

• Antiinflammatory and immunosupressive, so stress makes us more susceptible to disease
• Increased by alcohol and caffeine
• Chronically high can reduce memory