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2A - Endocrine System > The Adrenal Gland > Flashcards

The Adrenal Gland Flashcards

1
Q

Where are the adrenal glands located?

A

Superior pole of kidneys in retroperitoneal space

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2
Q

What does each adrenal gland weigh in an adult?

A

About 4g

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3
Q

What are the two seperate endocrine glands that makes up the adrenal gland?

A

Adrenal medulla

Adrenal cortex

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4
Q

What percentage of the adrenal gland is the adrenal medulla?

A

About 25%

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5
Q

What is the adrenal medulla?

A

Modified sympathetic ganglion derived from neural cresh tissue

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6
Q

What does the adrenal medulla secrete?

A

Catecholamines, mainly epinephrine, also norepinephrine and dopamine

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7
Q

What percentage of the adrenal gland is the adrenal cortex?

A

About 75%

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8
Q

What is the adrenal cortex?

A

True endocrine gland derived from mesoderm and secretes 3 classes of steroid hormones

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9
Q

What class of hormones does the adrenal cortex secrete?

A

Steroid

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10
Q

What are the 3 classes of steroid hormones that the adrenal cortex secretes?

A

Mineralocorticoids

Glucocorticoids

Sex steroids

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11
Q

What is an example of a mineralocorticoid?

A

Aldosterone (involved in regulation of Na and K)

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12
Q

What is an example of a glucocorticoid?

A

Cortisol (involved in maintaining plasma glucose)

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13
Q

What is an example of a sex steroid?

A

Testosterone

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14
Q

Is the adrenal cortex or medulla more superficial?

A

Adrenal cortex

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15
Q

What is each layer of the adrenal cortex?

A

Zona glomerulosa (secretes aldosterone)

Zona fasciculate (secretes glucocorticoids)

Zona reticularis (secretes sex hormones)

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16
Q

What does the zona glomerulosa secrete?

A

Aldosterone

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17
Q

What does the zona fasciculate secrete?

A

Glucocorticoids

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18
Q

What does the zona reticularis secrete?

A

Sex hormones

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19
Q

How is it possible for different hormones to be secreted in different layers of the adrenal cortex?

A

All steroid hormones are derived from cholesterol

But different enzymes found in different adrenal zones results in different end products

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20
Q

What is a synthetic pathway?

A

Route taken to build up a specific product

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21
Q

What enzyme is responsible for both the formations of aldosterone and cortisol?

A

21-hydroxylase

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22
Q

What does HPA stand for?

A

hypothalamic pituitary adrenal (central stress response system that intertwines the CNS and endocrine system)

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23
Q

What do defects in 21-hydroxylase cause?

A

Congenital adrenal hyperplasia resulting in:

  • deficiency of aldosterone and cortisol (so disruption of salt and glucose balance)
  • androgen biosynthesis is unaffected so accumulating steroid percursors are channels into excess adrenal androgen production
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24
Q

What does cortisol provide long loop feedback on?

A

CRH (Corticotropin-releasing hormone)

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25
Q

Cortisol provides long loop feedback on CRH as part of the hypothalamic-pituitary-adrenal pathway, what provides short-loop feedback?

A

ACTH

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26
Q

Explain the process of a deficit in 21-hydroxylase causing adrenal hyperplasia?

A

1) Lack of enzyme inhibits synthesis of cortisol
2) Removal of negative feedback on ACTH and CRH release
3) Increased ACTH secretion is responsible for enlargement of adrenal glands
4) Negative feedback of ACTH on CRH synthesis remains balanced
5) Babies become very ill within a few days of birth

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27
Q

What type of hormone is cortisol?

A

Glucocorticoid hormone (influences glucose metabolism)

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28
Q

What percentage of plasma cortisol is bound to carrier protein?

A

About 95%

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29
Q

What plasma protien does most cortisol bind to?

A

Cortisol binding globulin (CBG)

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30
Q

What kind of cells have cytoplasmic glucocorticoid receptors?

A

All nucleated cells

31
Q

What happens when cortisol binds to its cytoplasmic glucocorticoid receptor?

A

Hormone receptor complex migrates to nucleas

Binding to DNA via a hormone-receptor element to alter gene expression, transcription and translation

32
Q

What kind of rhythm do cortisol plasma levels show, and what are they preceded by?

A

Circadian rhythm, preceded by a similar pattern of release of ACTH

33
Q

Does cortisol or ACTH have a longer half life?

A

Cortisol, so bursts of release persist around longer than ACTH

34
Q

What time of day can the peak and lowest levels of plasma cortisol be obersed?

A

Peak - between 6am and 9am

Lowest - midnight

35
Q

What are fluctations of cortisol levels during the day due to?

A

Effects of stimuli which are related to stress

36
Q

What would a loss of cortisol mean?

A

Animals cannot deal with stress, particularly in terms of maintaining blood glucose levels

37
Q

How does cortisol cause gluconeogenesis?

A

Stimulates formation of gluconeogenic enzymes in liver, enhancing gluconeogenesis and glucose production

38
Q

Does cortisol have permissive action on insulin or glucagon?

A

Glucagon, which is vital as glucagon alone is inadequate in responding to a hypoglycaemia challenge

39
Q

What are the consequences of removing the adrenal glands in animals?

A

Cannot deal with stress, particularly in terms of maintaining blood glucose levels

Incapable of maintaining their ECF volume, an effect mediated by aldosterone

40
Q

What are some actions of cortisol on glucose metabolism?

A

Gluconeogenesis

Proteolysis

Lipolysis

Decreased insulin sensitivity

41
Q

Is excess cortisol diabetogenic or the opposite?

A

It is diabetogenic due to its gluocse-counter regulatory effects that oppose insulin

42
Q

Does cortisol have a positive or negative effect on calcium balance, and why?

A

Negative

Decreases absorption from gut, increases excretion at kidney resulting in net calcium loss

Also increase bone resorption, leading to osteoporosis

43
Q

Other than glucose metabolism, what are some additional actions of cortisol?

A
44
Q

How does cortisol cause an impairment on mood and cognition?

A

Depression and impaired cognitive function are strongly associated with hypercortisoaemia

45
Q

Does cortisol have permissive or antagonistic action to norepinephrine?

A

Permissive

Particular in smooth muscle (a-receptor effect is vasoconstrictive)

Cushing’s disease (hypercortisolaemia) is strongly associated with hypertension, and low cortisol levels are associated with hypotension)

46
Q

Does cortisol enhance or suppress the immune system, and why?

A

Suppression

Reduces the circulating lymphocyte count, reduces antibody formation and inhibits the inflammatory response

47
Q

What are some side-effects of glucocorticoid therapy?

A

Increases severity and frequency of infection (due to immune suppresion)

Muscle wastage (due to proteolysis)

Loss of percutaneous fat stores gives appearance of thinning skin

48
Q

What kind of hormone is aldosterone?

A

Mineralocorticoid

49
Q

What does aldosterone act on?

A

Distal tubule of kidney to determine to determine levels of minerals reabsorbed/excreted

50
Q

How does aldosterone impact sodium and potassium?

A

Increases reabsorption of sodium and promotes excretion of potassium

51
Q

What is secretion of aldosterone by adrenal cortex primarily controlled by?

A

Renin-angiotensin-aldosterone system (RAAS)

52
Q

What does RAAS stand for?

A

Renin-angiotensin-aldosterone system

53
Q

What system are the effects of aldosterone mainly on?

A

CNS system

54
Q

What does increased aldosterone cause?

A

Stimulates sodium (and water) retention and potassium depletion, resulting in increased blood volume and blood pressure

55
Q

What does decreased aldosterone cause?

A

Sodium (and water) loss and increased potassium in plasma, resulting in decreased blood volume and blood pressure

56
Q

What are some examples of disorders of the HPA?

A

Hypersecretion of cortisol

Hyposecretion of cortisol

57
Q

What are some causes of hypersecretion of cortisol?

A

Cushing’s syndrome/disease

58
Q

What is hypersecretion of cortisol most commonly due to?

A

Tumour in:

  • adrenal cortex (1o hypercortisolism), which is Cushing’s syndrome
  • pituitary gland (2o hypercortisolism), which is Cushing’s disease
59
Q

Does a tumour in the adrenal cortex cause Cushing’s disease or Cushing’s syndrome?

A

Cushing’s syndrome (1o hypercortisolism)

60
Q

Does a tumour in the pituitary cause Cushing’s disease or Cushing’s syndrome?

A

Cushing’s disease (2o hypercortisolism)

61
Q

Is hypersecretion or hyposecretion of cortisol more common?

A

Hypersecretion is much more common

62
Q

What causes hyposecretion of cortisol?

A

Addison’s disease

  • causes hyposecretion of all adrenal steroid hormones
  • due to autoimmune destruction of adrenal cortex
63
Q

What is Cushing’s disease characterised by?

A

Wasting of the extremities (due to catabolic action of cortisol)

Fat redistribution to the face (“moon face”) and trunk

64
Q

What are examples of things that disinhibit the hypothalamic-pituitary-axis (HPA)?

A

Alcohol, caffeine and lack of sleep

  • alcohol particularly depresses neurons involved in negative feedback, further enhancing stress effect and increasing levels of CRH and ACTH
  • turns down immune system and increases vulnerability to infection
65
Q

What is the adrenal medulla?

A

Modified sympathetic ganglion, not true endocrine tissue

66
Q

What happens to preganglionic fibres to the adrenal medulla?

A

Terminate on specialised postganglionic cells in adrenal medulla, these postganglionic cells do not have axons, instead releasing their neurohormones (adrenaline) into the blood

67
Q

What is an example of adrenal medulla pathology?

A

Pheochromocytoma

68
Q

What is pheochromocytoma?

A

Rare neuroendocrine tumour, found in adrenal medullar which results in XS catecholamines

Causing increased heart rare, increased cardiac output so massively increased blood pressure

Diabetogenic due to adrenergic effects on glucose metabolism

69
Q

What are some different sites of enodcrine pathology in HPA?

A

Secondary hypersecretion due to pathology in hypothalamus

Secondary hypersecretion due to pathology in anterior pituitary

Primary hypersecretion due to pathology in adrenal cortex

70
Q

In secondary hypersecretion due to pathology in hypothalamus, what are:

  • CRH levels
  • ACTH levels
  • cortisol levels

(high/low)

A

CRH levels - high

ACTH levels - high

Cortisol levels - high

71
Q

In secondary hypersecretion due to pathology in pituitary, what are:

  • CRH levels
  • ACTH levels
  • cortisol levels

(high/low)

A

CRH levels - low

ACTH levels - high

Cortisol levels - high

72
Q

In primary hypersecretion due to pathology in adrenal cortex, what are:

  • CRH levels
  • ACTH levels
  • cortisol levels

(high/low)

A

CRH levels - low

ACTH levels - low

Cortisol levels - high

73
Q

Why is care required when withdrawing chronic glucocorticoid treatment?

A

Due to enhanced negative feedback effects of exogenous control

Therapeutic cortisol also enhances negative feedback on hypothalamus and pituitary, reducing release of CRH and ACTH:

  • loss of trophic action of ACTH on adrenal gland causes atrophy of gland
  • risk of adrenal insufficiency if withdrawal is too fast

2A - Endocrine System (26 decks)

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