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Endocrine > The Adrenal Gland > Flashcards

The Adrenal Gland Flashcards

1
Q

Where are the kidneys located?

A

Superior pole of kidneys in retroperitoneal space

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2
Q

How does the anatomy of the adrenal veins differ?

A

Left adrenal vein drains into left renal vein

Right adrenal vein drains directly into IVC

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3
Q

Describe the structure of the adrenal glands

A 
Adrenal medulla (25%) 
Adrenal cortex (75%)
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4
Q

What does the adrenal medulla secrete?

A

Catecholamines (adrenaline, noradrenaline and dopamine)

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5
Q

What kind of tissue is the adrenal medulla?

A

It is a modified sympathetic ganglion derived from neural crest tissue

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6
Q

What kind of tissue is adrenal cortex?

A

True endocrine tissue derived from mesoderm

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7
Q

What hormones does the adrenal cortex secrete?

A

Mineralocorticoids
Glucocorticoids
Sex hormones

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8
Q

Give an example of a mineralocorticoid

A

Aldosterone

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9
Q

What is the role of aldosterone?

A

Involved in regulation of Na and K

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10
Q

Give an example of a glucocorticoid

A

Cortisol

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11
Q

What is the role of cortisol?

A

Involved in maintaining plasma glucose

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12
Q

How is the medulla arranged?

A

Surrounded by cortex and arranged into 3 concentric zones which produce different hormones

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13
Q

What are the different layers of the medulla and what do they produce?

A

Zona glomerulosa –> aldosterone
Zona fasciculata –> glucocorticoids
Zona reticularis –> sex hormones

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14
Q

How are all the different hormones in the adrenals made?

A

All steroid hormones, hence derived from cholesterol but different enzymes for the different end products are in each zone

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15
Q

What are the main products of the adrenal cortex?

A

Cortisol and aldosterone - these are essential for life

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16
Q

Apart from cortisol and aldosterone what products are made in the adrenals?

A

DHEA (prehormone of testosterone and oestrogen)

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17
Q

What causes congenital adrenal hyperplasia?

A

Defects in 21-hydroxylase (an enzyme essential for the synthesis of aldosterone and cortisol)

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18
Q

What are the features of congenital adrenal hyperplasia?

A

Disruption of salt and glucose balance
Androgen biosynthesis unaffected so accumulating steroid precursors channelled into excessive adrenal androgen production

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19
Q

Why does deficit in 21-hydroxylase causes adrenal hyperplasia?

A

Lack inhibits cortisol synthesis, this removes negative feedback on ACTH
Increased ACTH leads to enlargement of the adrenals

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20
Q

What is 95% of plasma cortisol bound to in the plasma?

A

Cortisol binding globulin

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21
Q

Which cells have receptors for glucocorticoids?

A

All nucleated cells have CYTOPLASMIC glucocorticoid receptors

Hormone receptor complex migrates to nucleus, binding DNA via hormone response element to alter gene expression, transcription + translation

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22
Q

When are cortisol levels at their highest?

A

6-9am

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23
Q

When are cortisol levels at their lowest?

A

Midnight

24
Q

What other things may cause fluctuation of cortisol levels throughout the day?

A

Other stimuli related to stress

25
Q

What does loss of cortisol result in?

A

Inability to cope with stress, esp. in terms of maintaining BG levels

Cortisol is critical in protecting the brain from hypoglycaemia

26
Q

How does cortisol impact BG?

A

Has permissive act on glucagon (glucagon alone is inadequate in responding to hypoglycaemic challenge)

27
Q

What are the actions of cortisol on glucose metabolism?

A

Gluconeogenesis
Proteolysis
Lipolysis
Decreases insulin sensitivity

28
Q

How does cortisol aid gluconeogenesis?

A

Stimulates formation of gluconeogenic enzymes

29
Q

How does cortisol aid proteolysis?

A

Stimulates muscle protein breakdown

30
Q

How does cortisol aid lipolysis?

A

Stimulates lipolysis in adipose tissue –> increase FFA in plasmsa

31
Q

Why is excess cortisol diabetogenic?

A

Cortisol acts to oppose insulin

32
Q

What are the non-glucocorticoid actions of cortisol?

A

Negative effect on Ca balance
Impaired cognitive function + depression in hypercortisolaemia
Permissive effects on NE
Suppression of immune system

33
Q

How does cortisol negatively effect Ca balance?

A

Decreases absorption from gut, increases excretion at kidney and increases bone resorption –> osteoporosis

34
Q

Why is Cushing’s disease (hypercortisolaemia) associated with HTN?

A

In vascular smooth muscle, cortisol has a permissive effect on NE so increases vasoconstriction

35
Q

True or false:

Low levels of cortisol are associated with HTN

A

False - low levels of cortisol are associated with hypotension

36
Q

How does cortisol suppress the immune system?

A

Reduces lymphocyte count, reduces antibody formation and inhibits inflammatory response

37
Q

What are the side effects of glucocorticoid therapy?

A

Immune suppression: increased freq. + severity of infections

Protein catabolism: muscle wasting

Lipolysis: loss of percutaneous fat gives thinning of skin appearance

For unknown reasons fat redistributed to trunk and face (moon face)

38
Q

What kind of hormone is aldosterone?

A

Mineralocorticoid

39
Q

Where does aldosterone act?

A

Distal tubule of kidney

40
Q

What is the role of aldosterone?

A

Increases resorption of Na

Promotes excretion of K

41
Q

Name the system that controls the secretion of aldosterone

A

Renin-angiotensin-aldosterone system (RAAS)

42
Q

What does increased levels of aldosterone lead to?

A

Increased Na and decreased K –> increased blood volume and increased BP

43
Q

What does decreased levels of aldosterone lead to?

A

Na loss and increased plasma K –> diminished blood volume and decreased BP

44
Q

What is hypersecretion of cortisol known as?

A

Cushing’s disease/syndrome

45
Q

What is the most common cause of hypersecretion of cortisol?

A

Pituitary tumour (cushing’s disease) - due to too much ACTH

46
Q

What other things can cause Cushing’s syndrome?

A

Adrenal tumour

Iatrogenic - too much cortisol administered

47
Q

What is the biggest cause of hyposecretion of cortisol?

A

Addison’s disease (hyposecretion of ALL adrenal steroid hormones)

48
Q

What causes Addison’s disease?

A

Autoimmune destruction of adrenal cortex

49
Q

How does alcohol affect ACTH/CRH?

A

It depresses the neurons involved in negative feedback further enhancing stress effect and increasing ACTH and CRH

–> inc. cortisol and immunosupression

50
Q

Describe the structure of the adrenal medulla

A

Preganglionic sympathetic fibres terminate on specialised postganglionic cells in the adrenal medulla (these do not have axons and release adrenaline into the blood directly)

51
Q

What is a phaeochromocytoma?

A

Tumour of the adrenal medulla which secretes xs catecholamines –> increased HR, increased BP

52
Q

How will the levels of CRH, ACTH and cortisol be affected by pathology in the hypothalamus?

A

CRH high
ACTH high
Cortisol high

53
Q

How will the levels of CRH, ACTH and cortisol be affected by pathology in the pituitary?

A

Low CRH
High ACTH
High cortisol

54
Q

How will the levels of CRH, ACTH and cortisol be affected by pathology in the adrenals?

A

Low CRH
Low ACTH
High cortisol

55
Q

Why do you have to be careful withdrawing chronic glucocorticoid treatment?

A

Additional therapeutic cortisol enhances negative feedback on hypothalamus + pituitary reducing release of CRH and ACTH

Loss of trophic action of ACTH on adrenal gland –> adrenal atrophy

Risk of adrenal insufficiency if withdrawal too fast

Endocrine (11 decks)

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