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Adrenal Gland Disorders Flashcards

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1
Q

Describe the structure of the adrenal gland

A
  • zona glomerulosa (outer cortex)
  • zona fasciculata (middle cortex)
  • zona reticularis (inner cortex)
  • adrenal medulla (centre of gland)
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2
Q

What hormone is produced by the zona glomerulosa ?

A

mineralocorticoid (aldosterone)

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2
Q

What is the structure of the Zona glomerulosa ?

A
  • cells arranged in clumps
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3
Q

What is the structure of the Zona fasciculata ?

A

cells arranged in cords alongside the blood sinusoids

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4
Q

What is the structure of the Zona reticularis ?

A

network of smaller cells

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5
Q

What is the structure of the adrenal medulla ?

A

loose network of neurosecretory cells surrounded by blood vessels

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6
Q

Function of the adrenal cortex

A

secretes 3 classes of steroid hormones
- glucocorticoids
- mineralocorticoids
- androgens

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7
Q

function of the adrenal medulla

A
  • part of the sympathetic nervous system
  • produces catecholamines (adrenaline and noradrenaline
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8
Q

What makes us the adrenal cortex ?

A
  • Zona glomerulosa
  • zona fasciculata
  • zona reticularis
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9
Q

What hormone is produced by the zona fasciculata ?

A

glucocorticoid (cortisol)

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10
Q

What hormone is produced by the zona reticularis ?

A

glucocorticoids & androgens

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11
Q

What are external stimuli that affect the control of glucocorticoid secretion

A
  • hypoxia
  • hypoglycaemia
  • stress
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12
Q

What internal stimuli is involved in the control of glucocorticoid secretion ?

A

diurnal rhythms

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13
Q

Define Diurnal Rhythms

A
  • 24 hr cycle of physiological events that are synchronised with environmental cues such as the light-dark cycle
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14
Q

How is the secretion of glucocorticoid stimulated ?

A
  • stimuli affects the hypothalamus
  • hypothalamus releases corticotrophin-releasing hormone
  • CRH acts on the pituitary gland
  • pituitary releases ACTH
  • ACTH acts on the adrenal cortex & triggers the release of glucocorticoids
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14
Q

What effect does cortisol have on the immune system ?

A

immune suppression

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15
Q

What effect does cortisol have on the liver ?

A

gluco-neogenesis

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16
Q

What effect does cortisol have on muscle ?

A

protein catabolism

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17
Q

What is another name for primary adrenal cortical hypofunction ?

A

Addison’s disease –> acute adrenal insufficiency

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17
Q

What effect does cortisol have on adipose tissue ?

A

lipolysis

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18
Q

What are some clinical features of Addison’s disease ?

A

lethargy, weakness, weight loss, anorexia, hypotension, hyperpigmentation

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18
Q

What causes Addison’s disease?

A
  • 90% of cases are autoimmune
  • remaining 10% can result from ; TB, tumour metastasis, amyloidosis, post adrenalectomy
  • withdrawal of glucocorticoids
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19
Q

What is the name of adrenal cortex hyper function the results in excess cortisol?

Study These Flashcards
A

Cushing’s syndrome

20
Q

What is the name of adrenal hyperfunciton with results in excess mineralocorticoid ?

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A

Conn’s Syndrome

21
What causes Conn's Syndrome?
- adrenal adenoma = 75% - bilateral hyperplasia of zona glomerulosa - adrenal carcinoma
22
What are some clinical features of Conn's syndrome?
hypertension, muscle weakness, tetany, paresthesia
23
Define tetany
muscle spasms
24
Define Paresthesia
abnormal sensation --> tingling or prickling
25
What are some clinical features of Cushing's syndrome ?
- moon face - proximal muscle wasting - purple striae - slow healing wounds
25
What can cause Cushing's disease?
- antieror pituitary tumour creating excess ATCH --> Excess glucocorticoid released - Adrenal carcinoma or adenoma - ectopic ACTH - usually produced by a tumour located elsewhere - iatrogenic cushings = too much glucocorticoids being taken (medication)
26
What are Catecholamines?
adrenaline and noradrenaline
27
What do catecholamines influence ?
- BP - cardiac output - fuel metabolism - sweating - pupil size
28
What are the metabolic effects of adrenaline?
- increase glycogen breakdown - gluconeogenesis - lipolysis - increase release of amino acids, lactate & pyruvate
29
What is Pheochromocytoma ?
- adrenal medulla hyperfunction - catecholamine secreting tumour
30
What are some clinical features of pheochromocytoma ?
- hypertension - vasomotor signs
31
What are vasomotor signs ?
anxiety, sweating, palpitations, tremors and abdominal pain
32
How is Cushing's syndrome Diagnosed ?
1. screening tests 2. establish cause
33
What are the 3 screening tests for Cushing's?
- 24h urine free cortisol - overnight dexamethasone suppression test - 48h low dose dexamethasone suppression test
34
Describe the overnight dexamethasone suppression test
- 1mg of Dexamethasone @ 11pm - 9am cortisol --> normal response = <50nmol/L - failure of suppression - Cushing's syndrome (also pseudocushings & stress?)
35
What is dexamethasone ?
- a synthetic glucocorticoid
36
What is the function of Dexamethasone ?
- suppresses pituitary ACTH - dexamethasone leads to suppression of cortisol
37
Describe the 48hr low dose dexamethasone suppression test
- 0.5 mg dexamethasone every 6hrs for 2 days - 9am cortisol day 2 - normal response - <50nmol/L - fewer false positives than overnight test
38
What are the functions of Glucocorticoids?
- increase hepatic glujconeogeneis & hepatic glycogen storage - increase breakdown of plasma & muscle protein to AA's - anti-inflammatory
39
Describe what might affect measuring Cortisol
- diurnal variation - levels high in morning & low/undetectable at night - part of stress response - some anti-inflammatory drugs may interfere in measurement
40
How do you measure Aldosterone ?
- measure after patient has been supine overnight & then upright - varies greatly with posture - usual to measure with renin
41
What are some biochemical signs of Adrenal Hypofunction?
- hyponatraemia - hyperkalaemia - hyperuricaemia - hypoglycaemia
42
What's the diagnostic approach for adrenal hypofucntion ?
- 9am cortisol - usually have to perform short synacthen test - then you need to establish primary or secondary - measure ACTH - ACTH High = primary - ACTH Low = secondary
43
Describe a Synacthen test
- measure baseline cortisol - give synacthen - measure cortisol - cortisol should increase to a value >550 nmol/L after 30 minutes
44
What are some biochemical signs of Conn's Syndrome?
- hypokalaemia - urinary potassium innaproriately high - high aldosterone & low renin
45
Describe Congenital Adrenal Hyperplasia
- inherited metabolic disorder of adrenal hormone secretion - autosomal recessive - 21-hydroxylase deficiency - can be partial or incomplete - 21-hydorxylase deficiency = increase in 17-hydroxyprogesterone
46
What are some clinical signs of classical Congential Adrenal Hyperplasia ?
Lack of cortisol & aldosterone --> adrenal crisis -dehydration -shock -death
47
Describe Non-Classical Congential Adrenal Hyperplasia
- milder non-life threatening - partial enzyme deficiency * low cortisol, normal aldosterone & androgens - premature pubic hair, menstrual irregularities, acne & fertility problems later
48
Describe diagnostic testing for Congenital Adrenal Hyperplasia
- Hormone measurement - 17-OHP - clinical evaluation
49
What are some treatments for CAH ?
- glucocorticosteroid - mineralocorticoid (classical form)
50
What is a possible treatment for a Pheochromocytoma ?
- surgical resection - beta-blocker to control BP
51
What does a positive result in a Synacthen test indicate ?
- adequate adrenal response - cortisol should increase to a value >550 nmol/L after 30 minutes with an increase of roughly 200nmol/L between baseline & 30 minute measure

Clinical Biochem (15 decks)

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