18. The Adrenal Glands

Question 1

What are the layers of the adrenal gland?

Answer 1

Capsule
Cortex - zona glomerulosa (mineralocorticoids), zona fasiculata (glucocorticoids), zona reticularis (glucocorticoids and androgens)
Medulla - chromatin cells

Question 2

What do corticosteroids do?

Answer 2

Affect gene transcription

Question 3

What are the types of corticosteroids?

Answer 3

Mineralocorticoids
Glucocorticoids
Androgens

Question 4

Give an example of a mineralocorticoid

Answer 4

Aldosterone

Question 5

Give examples of glucocorticoids

Answer 5

Cortisol
Corticosterone
Cortisone

Question 6

Give examples of androgens

Answer 6

Dehyrdroepiandrosterone

Androstenedione - testosterone and oestrogens

Question 7

Describe steroid hormones

Answer 7

Synthesised from cholesterol in adrenal glands and gonads
Lipid soluble hormones
Bind to receptors of the nuclear receptor family to modulate gene transcription

Question 8

How do corticosteroids work?

Answer 8

Readily diffuse across plasma membrane
Bind to glucocorticoid receptors
Binding causes dissociation of chaperone proteins
Receptor ligand complex trans locates to nucleus
Dimerisation with other receptors can occur
Receptors bind to glucocorticoid response elements (GREs) or other transcription factors

Question 9

Where is aldosterone synthesised and released from?

Answer 9

Zona glomerulosa of adrenal cortex

Question 10

What is the carrier protein of aldosterone?

Answer 10

Mainly serum albumin and to a lesser extent transcortin

Question 11

How does aldosterone work?

Answer 11

Aldosterone receptor is intracellular and exerts its actions by regulating gene transcription

Question 12

What is the role of aldosterone?

Answer 12

Regulation of plasma Na+, K+ and arterial blood pressure
Main actions in distal tubules and collecting ducts where it promotes expression of Na+/K+ pump promoting reabsorption of Na+ and excretion of K+

Question 13

What is primary hyperaldosteronism?

Answer 13

Too much aldosterone produced
Defect in adrenal cortex
Can be due to either bilateral idiopathic adrenal hyperplasia or aldosterone secreting adrenal adenoma (Conn’s syndrome)
Low renting levels

Question 14

What is secondary hyperaldosteronism?

Answer 14

Too much aldosterone produced
Due to overactivity of renin-angiotensin-aldosterone system (RAAS)
Can be due to renin producing tumour or renal artery stenosis
High renin

Question 15

What are the signs if hyperaldosteronism?

Answer 15

High BP
Left ventricular hypertrophy
Stroke
Hypernatraemia
Hypokalaemia

Question 16

What is the treatment for hyperaldosteronism?

Answer 16

Depends on type
Aldosterone producing adenomas removed by surgery
Spironolactone (mineralocorticoid receptor antagonist)

Question 17

Where is cortisol synthesised and released from?

Answer 17

Zonal fasiculata in response to ACTH

Negative feedback o hypothalamus inhibits CRH and ACTH release

Question 18

What is the carrier protein of cortisol?

Answer 18

Transcortin

Question 19

How does the cortisol receptor exert its actions?

Answer 19

By regulating gene transcription

Question 20

What are the actions of cortisol?

Answer 20

Increased protein breakdown in muscles
Increased lipolysis in fat
Increased gluconeogenesis in liver
Resistance to stress
Anti-inflammatory effects
Depression of immune system

Question 21

What are the net effects of glucocorticoid on metabolism?

Answer 21

Increased glucose production
Breakdown of protein
Redistribution of fat

Question 22

What are the external causes of Cushing’s syndrome?

Answer 22

Prescribed glucocorticoids

Question 23

What are the endogenous causes of Cushing’s syndrome?

Answer 23

Benign pituitary adenoma secreting ACTH (Cushing’s disease)
Excess cortisol produced by adrenal tumour (Adrenal Cushing’s)
Non pituitary-adrenal tumours producing ACTH or CRH e.g. in small cell lung cancer

Question 24

What are the signs and symptoms of Cushing’s syndrome?

Answer 24

Plethoric moon-shaped face
Buffalo hump
Abdominal obesity
Purple striae
Acute weight gain
Hyperglycaemia
Hypertension

Question 25

What are the signs and symptoms of Addison’s disease?

Answer 25

``` Postural hypotension Lethargy Weight loss Anorexia Increased skin pigmentation Hypoglycaemia ```

Question 26

What is Addison’s disease?

Answer 26

Chronic adrenal insufficiency | Most common cause is destructive atrophy from autoimmune response

Question 27

Why does hyperpigmentation occur in Addison’s disease?

Answer 27

``` Decreased cortisol Negative feedback on anterior pituitary reduced More POMC required to syntheses ACTH Increased POMC leads to increased MSH MSH promotes melanin synthesis ```

Question 28

What is Addisonian crisis?

Answer 28

Life threatening emergency due to adrenal insufficiency

Question 29

What is addisonian crisis precipitated by?

Answer 29

``` Sever stress Salt deprivation Infection Trauma Cold exposure Over exertion Abrupt steroid drug withdrawal ```

Question 30

What are the symptoms of addisonian crisis?

Answer 30

``` Nausea Vomiting Pyrexia Hypotension Vascular collapse ```

Question 31

What is the treatment for addisonian crisis?

Answer 31

Fluid replacement | Cortisol

Question 32

What is male dehydroepiandrosterone (DHEA) converted to?

Answer 32

Testosterone in testes | After puberty this is insignificant since testes release for more testosterone themselves

Question 33

What do adrenal androgens do in females?

Answer 33

Promote libido and are converted to oestrogens by other tissues After menopause this is only source of oestrogens

Question 34

What is phaeochromocytoma?

Answer 34

Chromatin cell tumour | Rare, catecholamine-secreting tumour

Question 35

What are the characteristics of phaeochromocytoma?

Answer 35

``` Severe hypertension Headaches Palpitations Diaphoresis Anxiety Weight loss Elevated blood glucose ```