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Z- Endocrinology > The adrenal gland > Flashcards

The adrenal gland Flashcards

1
Q

where do the adrenal glands sit?

A

on top of there kidneys

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2
Q

what are the two parts of the adrenal gland?

A
  • adrenal cortex

- adrenal medulla

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3
Q

what are the 3 parts of the adrenal cortex?

A
  • zone glomerulosa
  • zone fasciculate
  • zone reticular
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4
Q

what does the zone glomerulosa produce?

A

aldosterone

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5
Q

what does the zone fasciculata and zone reticular produce?

A

cortisol and androgens

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6
Q

what cells make up the medulla and what do they produce?

A

chromaffin cells produce adrenaline and noradrenaline

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7
Q

what is the blood flow in the adrenal gland and what does this lead to?

A

from the outside cortex to the medulla

- chromaffin cells are exposed to high concentration of hormones produced in the cortex

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8
Q

what is the chromaffin cells innervated by?

A

sympathetic branch of autonomic nervous

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9
Q

what are the 3 major classes of steroid hormones?

A
  1. Glucocorticoids
  2. Mineralocorticoids
  3. Sex steroids
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10
Q

what are the 4 principal hormones that the adrenal glands produce?

A
  1. Cortisol (a glucocorticoid)
  2. Aldosterone (a mineralocorticoid) – covered in renal
  3. Adrenaline (a.k.a. epinephrine)
  4. Noradrenaline (a.k.a. norepinephrine)
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11
Q

what other hormones are produced from adrenal glands?

A

androgenic steroids

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12
Q

what is the function of cortisol?

A

It acts to increase plasma [glucose] by enhancing mobilisation of AAs in many tissues and to enhance the ability of the liver to convert these AAs into glucose by activating gluconeogenesis

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13
Q

Once secreted , what does cortisol bind to?

A
  • 90% of cortisol is transported bound to corticosteroid-binding globulin (CBG; a.k.a. transcortin)
  • ~7% bound to albumin
  • 3-4% of circulating cortisol is free
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14
Q

what type of receptor does cortisol bind to?

A

cytoplasmic receptor that translocates to the nucleus and modulates transcription in various tissues

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15
Q

how does cortisol affect the liver?

A

Cortisol induces synthesis of enzymes involved in metabolism of AAs, facilitating conversion to glucose through gluconeogenesis

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16
Q

how does cortisol affect skeletal muscle?

A

Cortisol stimulates protein breakdown, releasing AAs to be used by the liver

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17
Q

how does cortisol affect adipose tissue?

A

Cortisol induces mobilisation of fat from sub-cutaneous stores. FAs released can be used as an alternative fuel to glucose and increase availability of glucose.
(For unknown reasons, although fat is mobilised from the extremities, some is also deposited centrally)

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18
Q

what secretes ACTH and what behaviour does it show?

A
  • pituitary

- circadian and pulsatile behaviour

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19
Q

what are the causes of glucocorticoid excess?

A
  • Seen clinically in individuals prescribed glucocorticoids

- Less commonly as a result of a tumour (primary or secondary)

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20
Q

what are the symptoms of glucocorticoid excess ( Cushing syndrome)

A
  • Hypertension
  • Loss of sub-cutaneous adipose and connective tissue in the extremities
  • Loss of bone mineral (osteoporosis)
  • Hyperglycemia
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21
Q

what also produces these side effects?

A

Glucocorticoid drugs with anti-inflammatory actions also produce these side-effects

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22
Q

what are the symptoms of adrenal insufficiency?

A
  • Failure of adrenal cortical hormone secretion leads to increases in circulating concentrations of ACTH
  • Lack of glucocorticoid: predisposes to hypoglycemia
  • Lack of aldosterone: hyperkalemia
  • Combined absence: leads to hypotension
23
Q

what is the most common cause of adrenal insufficiency?

A

autoimmune adrenal disease

24
Q

what is the function of aldosterone?

A

[Aldosterone determines extracellular fluid (ECF) volume by regulating ECF Na+]
-Na+ is the primary osmotically active particle in ECF, therefore the amount of Na+ that is present determines the ECF volume
ECF volume is a prime determinant of arterial BP, therefore aldosterone plays an important role in the maintenance of BP

25
Q

what is the primary regulator of ECF osmolarity?

A

aldosterone

26
Q

what is the primary regulator of ECF volume?

A

ADH

27
Q

how is aldosterone produced?

A

glomerulosa cells of the adrenal cortex synthesise aldosterone from cholesterol, through progesterone

28
Q

what secretagogues enhance secretion?

A

(in order of influence):

  • Peptide hormone ANG II
  • Increase in extracellular [K+]
  • (ACTH weakly promotes aldosterone secretion)
29
Q

what does aldosterone bind to once its secreted?

A

~37% remains free in plasma. The rest weakly binds to CBG (~21%) and albumin (~42%).

30
Q

what is the difference for affinity of CBG for cortisol and aldosterone?

A

The affinity of CBG for cortisol is ~30-fold higher than aldosterone

31
Q

what effects does aldosterone have on Na+ and K+ ?

A

Aldosterone stimulates Na+ reabsorption and K+ excretion by the renal tubule

32
Q

what can loss of aldosterone-mediated Na+ reabsorption lead to?

A

Hyperkalemia

Hypotension

33
Q

what can excess aldosterone secretion produce?

A

Hypokalemia

Hypertension

34
Q

what is effective in reducing BP during hypertension in patients?

A

ACE inhibitors

35
Q

what action does aldosterone take during hypotension?

A

Aldosterone secretion increases, increasing effective circulating volume and BP

36
Q

what action does aldosterone take during congestive heart failure?

A

Aldosterone secretion increases – exacerbates the condition

37
Q

what can tumours of the glomerulosa cells lead to?

A

hyperaldosteronism (Conn syndrome)

  • Patients develop hypertension and hypokalemia
  • Plasma [renin] is suppressed
38
Q

what do both adrenaline and noradrenaline do?

A

enter the circulation and act on distal tissues

39
Q

where is the only place adrenaline is produced?

A

adrenal medulla

40
Q

what are both adrenaline and noradrenaline derived from?

A

the amino acid - tyrosine

41
Q

During a fight-or-flight response, what actions do adrenaline and noradrenaline do?

A
  • Combined neuroendocrine response is activated within seconds
  • Secreted catecholamines act very quickly after reaching their target tissues
  • The biological actions of catecholamines are very brief (lasting only ~10 seconds in the case of adrenaline)
42
Q

List some neuroendocrine responses.

A
  • Increases in HR and contractility
  • Mobilisation of fuel stores from skeletal muscle and fat
  • Piloerection
  • Pupillary dilatation
  • Increased sphincter tone of the bowel and bladder
43
Q

what do adrenaline and noradrenalin bind to and what do they act through?

A

bind to alpha and beta adrenoreceptors on the cell surface and act through heterotrimeric G proteins

44
Q

Can adrenaline and noradrenaline bind to individual adrenoreceptors?

A

Yes- but normally with different affinities

45
Q

During exercise, what is circulating adrenaline important for?

A
  • mediating an increase in blood flow to skeletal muscle
  • relaxation of bronchial smooth muscle
  • activation of the degradation of muscle glycogen to provide a ready fuel source
  • activation of lipolysis in adipose tissue to release FFAs for more sustained muscle activity if needed
  • activation of glycogenolysis in liver, maintaining the supply of glucose in the blood
46
Q

what is the net effect pf circulating adrenaline during exercise?

A

Promote glycogenolysis while maintaining glycemia so that brain function is not impaired

47
Q

what controls catecholamine secretion?

A

Unlike other glandular tissue, no endocrine feedback loop regulates the secretion of adrenal medullary hormones,
it is controlled by the CNS

48
Q

what happens in response to mild hypoglycaemia?

A
  • Decrease in blood glucose is sensed by the CNS
  • This triggers an increase in sympathetic output which inhibits insulin secretion and promotes an increase in blood [glucose]
  • Increased sympathetic output to the adrenal medulla also triggers release of adrenaline
  • Adrenaline acting on the liver stimulates glycogenolysis which helps restore blood [glucose] to normal
  • Restoration of blood [glucose] to normal diminishes central sympathetic output
49
Q

where is androgen produced in both males and females?

A

adrenal gland

50
Q

name 3 androgenic steroids.

A
  • DHEA (dehydroepiandrosterone) and
  • Androstenedione
  • (Plus small amounts of estrogens and some glucocorticoids)
51
Q

what is androgenic steroids important during?

A

fetal development

52
Q

what effect does adrenal androgens have on females?

A

-Responsible for growth of axillary and pubic hair

53
Q

what effect does adrenal androgens have on males?

A

-Early development of male sex organs but Over-ridden by testosterone during late puberty and adulthood

Z- Endocrinology (9 decks)

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