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Adrenal structure and function Flashcards

1
Q

Where are the adrenal glands located?

A

Above the kidneys

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2
Q

What are the layers of the adrenal gland (5)?

A 
Medulla
Zone reticularis (cortex)
Zone fasciculata (cortex)
Zona glomerulosa (cortex)
Capsule
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3
Q

What adrenohormones are produced in the cortex?

A

Zona gomerulosa=mineralocorticoids (aldosterone)
Zona fasciculata=glucocorticoids (cortisol)
Zona reticularis= androgens

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4
Q

What adrencortical hormones are produced in the medulla?

A

Catecholamines (adrenaline and noradrenaline)

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5
Q

What is the function and control of the zona glomerulosa?

A

Outer layer
Minerolocorticoid (aldosterone)
Function: salt
Control: renin

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6
Q

What is the function and control of the zona fasciculata?

A

Middle layer
Glucocorticoid (cortisol)
Function=sweet
Control=ACTH

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7
Q

What is the function and control of the zona reticulata?

A

Inner layer
Sex steroids (DHEA, DHEAS)
Function=sex
Control ACTH

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8
Q

What is the function and control of the medulla?

A

Adrenaline/ noradrenaline
Function=fight or flight
Control=sympathetic nervous system

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9
Q

What is adrenocorticotropic hormone (ACTH)?

A

Hormone produced in the anterior, or front pituitary Gland in the brain. Regulates levels of cortisol

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10
Q

Describe the structure of steroid hormones

A

All derived from cycopetanoperhydrophenanthrene (all have 3 cyclohexane rings and a single cyclopentane ring)

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11
Q

What is the purpose of the HPA axis?

A

Regulation of glucocorticoid secretion

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12
Q

Describe the HPA axis

A

CRH (from hypothalamus) -> ACTH release (anterior pituitary) -> cortisol release (from adrenal cortex) -> cortisol -ve feedback on CRH and ACTH.

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13
Q
  1. How does stress affect HPA axis?

2. What effect does cortisol have on the immune system

A
  1. People who are stressed have overactive HPA axis

2. Decreases immune response

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14
Q

What are the systemic effects of cortisol release?

A

Gluconeogenesis
Protein mobilisation
Fat mobilisation
Decreased inflammation

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15
Q
  1. How does cortisol levels affect sleep

2. How may this be affected

A
  1. Cortisol levels are low at night to promote sleep
  2. Cushing’s disease (excess cortisol), cortisone treatment, chronic stress, diurnal variation lost in Cushing syndrome (test for high midnight cortisol), night shifts, jet lag, exogenous steroids
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16
Q

How is aldosterone regulated?

A

RAAS

Aldosterone can be increased due to: increased ang II, increased potassium, increased ACTH, decreased sodiu

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17
Q

Describe the process of aldosterone regulation

A

Dehydration/Na+ deficiency/haemorrhage -> decreased blood vol. and pressure -> juxtagomerular cells increase renin -> angiotensinogen converted to ang I -> ACE (lungs) converts Ang I to Ang II -> adrenal cortex increases aldosterone (also vasoconstriction of arterioles) -> kidneys increase Na+ and H2O reabsorption and increased H+ and K+ secretion -> blood vol and pressure return to normal

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18
Q

What are the functions of aldosterone?

A

Increased Na+ and H2O reabsorption to increase blood vol.

Increase K+ and H+ secretion

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19
Q

What are the effects of aldosterone?

A

Increase renal tubular re-absorption of sodium and secretion of potassium
Increases ECF volume
Increases arterial pressure

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20
Q

What is the significance of the structures of glucocorticoids and mineralocorticoids?

A

They look similar due to ring structure

Cortisol can act as a mineralocorticoid and bind to these receptors and cause similar effects to aldosterone

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21
Q
  1. What prevents cortisol binding to mineralocorticoid receptors
  2. What are the issues with this
  3. Why is this clinically important
A
  1. 11 beta-HSD2 inactivates cortisol to cortisone so prevents it binding to mineralocorticoid receptors
  2. Serum conc of cortisol is 2000X of aldosterone so if too much cortisol it can escape the effects of 11 beta-HSD2
  3. In adrenal insufficiency don’t give mineralocorticoid if giving corticosteroids
22
Q

1 What food in high concentrations can cause apparent mineralocorticoid excess?
2. What condition may apparent mineralocorticoid excess be seen in?

A
  1. Liquorice as it can inhibit 11 beta-HSD2

2. Cushing’s

23
Q

Give examples of

  1. Active steroids
  2. Inert steroids
A
  1. Cortisol, corticosterone, prednisolone

2. Cortisone, 11-dehydrocorticosterone, prednisone

24
Q

What are the effects of glucocorticoids?

A

Gluconeogenesis (type II diabetes)
Inhibit protein synthesis
Increase protein breakdown (muscle wasting in Cushing’s sydrome)
Stimulate lipolysis
Immunologic and inflammatory responses (delayed wound healing)

25
What are corticosteroids?
Refers to both glucocorticoids and mineralocorticoids but often used as a synonym for glucocorticoid
26
What is phaeochromocytoma?
Rare tumour of adrenal gland that results in too much adrenaline and noradrenaline being produced. Difficult to detect due to short half live of adrenaline and noradrenaline. Urine catecholamines or metanephrins are measured instead
27
What is the role of the adrenal medulla?
Catecholamines released in response to exercise or imminent danger Adrenaline 80% / noradrenaline 20% These have a half life of 2 minutes Fight or flight response
28
Describe the fight or flight response?
Increased HR Vasoconstriction Bronchiole dilation Increased metabolism
29
What is Addison’s disease?
Primary adrenal insufficiency/hypoadrenaism-insufficient cortisol
30
What is Conn’s syndrome?
Primary aldosteronism/hyperaldosteronism-excess aldosterone
31
What is Cushing’s disease?
Benign tumour (adenoma) forms in pituitary glands causing excessive release of ACTH and elevated cortisol production (excess cortisol)
32
What is 1. Primary adrenal insufficiency 2. Secondary adrenal insufficiency 3. Tertiary adrenal insufficiency
1. Problem with adrenal gland 2. Lack of ACTH 3. Lack of CRH
33
Give an example of primary adrenal insufficiency
``` Addison’s disease 120 per million 80% due to auto-immune adrenalitis 75% have positive antibodies 50% have other autoimmune conditions (pernicious anaemia, Grave’s disease, type I diabetes) ```
34
What are the signs and symptoms of Addison’s disease?
``` Hyperpigmentation in gums Skin creases Low BP Weakness Weight loss Nausea/diarrhoea/vomiting/constipation/abdominal pain Vitiligo ```
35
What are the signs and symptoms of adrenal crisis?
``` Fever Syncope Convulsions Hypoglycaemia Hyponatraemia Severe vomiting and diarrhoea ```
36
What are the causes of Addison’s disease?
Autoimmune Infection (TB, fungal, CMV) Infiltration (metastasis, lymphoma, amyloidosis) Infarction (thrombophilia) Haemorrhage (meningococcal septicaemia, pseudomonas, anticoagulants (Waterhouse-Frederichsen syndrome=meningococcal sepsis with bilateral adrenal haemorrhage) Adrenoleukodystrophy (ALD)=inherited, affects genes responsible for peroxisome activation so damage adrenal gland, brain, myelin
37
What is Adrenal crisis/addisonian crisis?
Hormonal factor precipitating adrenal crisis is mineralocorticoid not glucocorticoid Manifests as hypotensive shock Rarely hypoglycaemic Total loss of adrenocortical function causes death in 3 days-2 weeks
38
What is the immediate treatment for adrenal crisis?
Fluids 1-3L of 0.9% saline in first 12-24 hours Hypoglycaemia: IV dextrose Glucocorticoids: hydrocortisone 100mg stat, 100mg IV 6 hourly Precipitating cause should be treated
39
What is the long term treatment of adrenal crisis?
Hydrocortisone-10mg morning, 5mg lunch, 5mg evening (difficult to mimic circadian rhythm) Fludrocortisone 100mcg daily Androgen replacement: DHEA 25-50mg daily In secondary adrenal insufficiency HPA axis suppression means dose should be reduced gradually
40
What is the sick day rules for adrenal crisis?
Never stop steroids Double dose during illness/infection If unable to take PO hydrocortisone, need IM/IV hydrocortisone Carry steroid card/medicAlert bracelet
41
What is secondary adrenal insufficiency?
HPA axis suppression due to long term steroid use Pituitary/hypothalamic disease Clinical presentations similar but no hyperpigmentation, no dehydration or hyperkalaemia, hypoglycaemia is more common
42
What is Cushing’s syndrome/
Prolonged exposure to elevated levels of glucocorticoids Most commonly due to exogenous corticosteroid use Suppression of HPA axis which can las years
43
What are the symptoms of Cushing’s syndrome?
``` Acne Moon face More body and facial hair Weight gain Purple striae Pendulous abdomen Slow wound healing Ecchymosis Thin skin and subcutaneous tissue Thin extremities with muscle atrophy Supraclavicular fat pad Buffalo hump Red cheeks Thinning of hair ```
44
What is the difference between Cushing’s sydrome and Cushing’s disease?
Sydrome=due to any cause of hypercortisolism | Disease=ACTH producing pituitary adenoma causing hypercortisolaemia
45
What are the types of Cushing’s syndrome?
ACTH dependent (pituitary adenoma, 60-70%, ectopic ACTH production) ACTH independent (majority due to exogenous steroids 80-90%, adrena adenomas/carcinomas 10-20%)
46
What is a differential diagnosis for Cushing’s
Pseudo Cushing’s states
47
What can cause high CRH
``` Stress Alcoholism Depression Obesity Anorexia Bulimia ```
48
How do you make a diagnosis of Addison’s disease?
Random cortisol-levels are variable through day so may miss it 9am cortisol- cortisol <100nmol=insufficiency Short syncathen / ACTH stimulation tests (definitive test used)
49
What is short synacthen test?
0 mins-sample for cortisol at baseline then give synthetic ACTH (synacthen) injection IM of IV 30 mins-take sample for cortisol Normal response is 30 min cortisol >540 nmol/L
50
How is Cushing’s screened for?
24 hr urine rest, measuring free cortisol 1mg overnight dexamethasone suppression test Midnight serum cortisol (not really used) Late night salivary cortisol
51
Describe the overnight dexamethasone suppression test?
``` 1mg dexamethasone at 11pm 9am measure cortisol Normal=<50nmol/L Sensitivity 98% False positives Decreased absorption Increased dexamethasone clearance (anti-convulsants) Increase in CBG (oestrogen) Pseudo-Cushing’s states ```
52
What are other associated laboratory abnormalities with adrenal disease?
Raised WBC Hyperglycaemia Hypokalaemia metabolic alkalosis

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