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*Diabetes & Endocrinology > Adrenal Gland > Flashcards

Adrenal Gland Flashcards

1
Q

Describe where adrenal glands are situated and how they are peritonised

A

Situated on superior pole of kidney

Retroperitoneal

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2
Q

Describe the venous drainage of the R adrenal v L adrenal

A 
Left adrenal vein drains into left renal vein
Right adrenal (usually) drains directly into IVC
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3
Q

What 2 quite separate endocrine glands is the adrenal gland split into?

A 
Adrenal Medulla (~25%)
Adrenal Cortex (~75%)
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4
Q

What is the adrenal medulla?

A

Modified sympathetic ganglion derived from neural crest tissue (neuro)

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5
Q

What does the adrenal medulla secrete?

A 
CATECHOLAMINES
mainly epinephrine (adrenaline), also norepinephrine + dopamine
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6
Q

What is the adrenal cortex?

A

True endocrine gland derived from mesoderm (endo)

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7
Q

What does adrenal cortex secrete?

A

3 classes of STEROID hormones

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8
Q

What are the 3 classes of steroid hormones secreted by the adrenal cortex?

A
  1. Mineralocorticoids e.g. aldosterone
  2. Glucocorticoids e.g. cortisol
  3. Sex steroids e.g. testosterone
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9
Q

Both parts of adrenal gland play a role in the body’s response to what?

A

Stress

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10
Q

What 2 hormones secreted by the adrenal cortex are essential for survival?

A

Aldosterone

Cortisol

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11
Q

How are the cortex and medulla arranged with respect to each other?

A

Cortex surrounds medulla

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12
Q

How is the cortex arranged for its function?

A

in 3 concentric zones which produce different hormones

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13
Q

What are the 3 zones of the adrenal cortex?

A

Zone glomerulosa
Zona fasciculata
Zona reticularis

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14
Q

What hormones do each of the zones produce?

A

ZG - aldosterone
ZF - glucocorticoids
ZR - sex hormones

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15
Q

What type of hormones does the adrenal gland produce in general?

A

Steroid

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16
Q

Although all adrenal gland hormones are steroid, how are different end products produced from diff zones?

A

Different enzymes are found in different zones

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17
Q

What are the 2 main products of the adrenal cortex?

A

Cortisol

Aldosterone

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18
Q

What is DHEA (dehydroepiandrosterone)?

A

Pre-hormone of testosterone and oestrogen - marked decline with age

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19
Q

In the pathway for synthesis of which hormones is 21-hydroxylase enzyme found?

A

Aldosterone (from corticosterone)

Cortisol

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20
Q

What are defects in 21-hydroxylase enzyme a common cause of?

A

Congenital adrenal hyperplasia

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21
Q

What does congenital adrenal hyperplasia result in?

A

Deficiency of aldosterone and cortisol and associated disruption of salt and glucose balance

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22
Q

What happens to androgen biosynthesis in congenital adrenal hyperplasia?

A

Unaffected; accumulating steroid precursors are channelled into excessive adrenal androgen production

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23
Q

How do babies with CAH present?

A

Malformed/ambiguous genitalia due to huge excess of sex steroids and underexposure of glucocorticoids
Leaves them incredibly ill in a matter of days - need aldosterone for BP etc

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24
Q

Describe the hypothalamic-pituitary-adrenal pathway

A 
>Hypothalamus
>CRH (corticotropin-releasing hormone)
>Anterior pituiary 
> ACTH (adrenocorticotropic hormone)
>Adrenal cortex 
>Cortisol
>Target tissue
>Response
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25
Q

What is the short loop feedback in this pathway?

A

ACTH on CRH

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26
Q

What is the long loop feedback in this pathway?

A

Cortisol on CRH

27
Q

Why does a deficit of 21-hydroxylase cause adrenal hyperplasia (4 steps)?

A
  1. Lack of 21-hydroxylase inhibits synthesis of cortisol
  2. This removes neg feedback on ACTH + CRH
  3. Increased ACTH secretion is responsible for enlargement of adrenal glands
  4. Neg feedback of ACTH on CRH synthesis remains
28
Q

Steroid yeah, but what specific type of hormone is cortisol?

A

Glucocorticoid

29
Q

What does the name glucocorticoid suggest?

A

it influences glucose metabolism

30
Q

How is ~95% of plasma cortisol found?

A

Bound to a carrier protein (cortisol binding globulin (CBG))

31
Q

Which cells have cytoplasmic glucocorticoid receptors?

A

ALL nucleated cells

32
Q

Describe the mechanism of steroid hormone function in the cell

A

Unbound hormone enters cell and binds to cytoplasmic receptor
Hormone receptor complex migrates to nucleus, binding to DNA via a hormone-response element to alter gene expression
Activated genes create new mRNA that moves back to cytoplasma
Translation produces new proteins for cell processes

33
Q

Do steroid hormones only bind to cytoplasmic receptors?

A

No; some can bind to cell surface receptors to produce rapid responses

34
Q

What characteristic pattern do plasma levels of cortisol show?

A

A marked circadian rhythm; peak is 6-9am, nadir is midnight; other fluctuations are due to effects of other stressful stimuli

35
Q

Cortisol as a glucocorticoid is crucial for what?

A

Helping to protect brain from hypoglycaemia

36
Q

What action does cortisol have on glucagon?

A

Permissive

vital as glucagon alone is inadequate

37
Q

What 4 things does cortisol influence to impact glucose metabolism?

A
  1. Gluconeogenesis
  2. Proteolysis
  3. Lipolysis
  4. Decreases insulin sensitivity of muscles + adipose tissue
38
Q

How does cortisol impact gluconeogenesis?

A

Stimulates formation of gluconeogenic enzymes in liver thus enhancing gluconeogenesis + glucose production

39
Q

How does cortisol impact proteolysis?

A

Stimulates breakdown of muscle protein to provide gluconeogenic substrates for liver

40
Q

How does cortisol impact lipolysis?

A

Stimulates lipolysis in adipose tissue which increases FFA in plasma creating alt fuel for protection of BG while also creating glycerol substrate for gluconeogenesis

41
Q

Cortisol acts to oppose insulin in these glucose counter-regulatory effects and so what does this mean about glucose?

A

It is diabetogenic

42
Q

How are the effects cortisol different from GH?

A

Cortisol is catabolic to proteins

43
Q

Give 4 additional actions of cortisol (non-glucocorticoid)

A
  1. Negative effect on Ca2+ balance
  2. Impairment of mood and cognition
  3. Permissive effects on norepinephrine
  4. Suppression of the immune system
44
Q

How does cortisol exhibit a negative effect on Ca2+ balance?

A

Decreases absorption from gut
Increases excretion at kidney
(also increase bone resorption - osteoporosis)

45
Q

What symptoms does cortisol’s permissive effects on norepinephrine present as in Cushings?

A

Hypertension

46
Q

How does supperession of immune system by cortisol occur?

A

Reduces circulating lymphocyte count
Reduces antibody formation
Inhibits inflammatory response - this can be useul clinically (asthma, UC, transplant)

47
Q

Steriod, but what specific class of hormone is aldosterone?

A

Mineralocorticoid

48
Q

Describe the action of aldosterone as a mineralocorticoid?

A

Acts on the distal tubule of the kidney to determine the levels of minerals reabsorbed/excreted

49
Q

How does aldosterone determine mineral levels?

A

Increases resabsorption of Na+ ions and promotes excretion of K+ ions

50
Q

How is secretion of aldosterone by the adrenal cortex controlled?

A

Renin-angiotensin-aldosterone pathway (RAAS)

51
Q

Describe the end effects of increased aldosterone

A

Stimulates Na+ (and H2O) retention + K+ depletion = increased blood vol = increased BP

52
Q

Describe the end effects of decreased aldosterone

A

Na+ (and H2O) loss and increased plasma K+ = decreased blood vol = decreased BP

53
Q

2 causes of hypersecretion of cortisol

A

Cushing’s syndrome/disease

Iatrogenic (too much cortisol administration)

54
Q

Difference between Cushings syndrome and Cushings disease?

A

Syndrome - tumour in adrenal cortex

Disease - tumour in pituitary gland (most common)

55
Q

Give a cause of hyposecretion of cortisol

A

Addisons disease

56
Q

What is Addisons?

A

Hyposecretion of all adrenal steroid hormones

Due to autoimmune destruction of adrenal cortex

57
Q

Some signs of Cushings?

A

Fat deposits at base of neck, back, trunk, around face

Wasting of extremities

58
Q

(interest) Why is there an increasing interest in CRH and ACTH?

A

May be a key link in how mental state affects immune system
Alcohol, caffeine and lack of sleep all “disinhibit” the Hypothalamo-Pituitary-Adrenal Axis (HPA)
Subsequent elevation of cortisol levels turn down immune system

59
Q

Do post-ganglionic fibres in adrenal medulla have axons?

A

No, they release neurohormones (adrenaline) directly into blood

60
Q

What is a pheochromocytoma?

A

Rare neuroendocrine tumour found in the adrenal medulla which results in XS catecholamines

61
Q

Why is care required when withdrawing glucocorticoid treatment?

A

Enhanced negative feedback effects of exogenous cortisol

62
Q

What is the risk of withdrawing glucocorticoid treatment too fast?

A

Loss of trophic action of ACTH on adrenal gland causing atrophy of gland and risk of adrenal insufficiency

63
Q

What are some side effects of glucocorticoid therapy?

A

Loss of percutaneous fat stores = thinning skin
Increased severity and frequency of infection
Muscle wastage
(look at diagram)

*Diabetes & Endocrinology (24 decks)

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