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SGUL - Physiology 1 > Disorders of Adrenocortical Dysfunction > Flashcards

Disorders of Adrenocortical Dysfunction Flashcards

1
Q

What are the three stages of Cushing’s Disease investigation?

A
  • Screening Tests, for when the disease is suspected
  • Confirmation of the Diagnosis
  • Differentiation of the Cause
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2
Q

What are the screening tests for Cushing’s Disease?

A
  • Urinary-free cortisol
  • Diurnal rhythm
  • Overnight dexamethasone suppression testing
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3
Q

Describe the overnight low-dose dexamethasone suppression test.

A
  • Cortisol is to be measured at 8 AM.
  • 1 mg of dexamethasone is given at 11 PM. The cortisol levels are measured again at 8 AM the next morning.
  • Cortisol suppression to <50 nmol/l is normal.
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4
Q

If the screening tests for Cushing’s Disease come back positive, there are 3 possibilities that could cause that.
What are these three possibilities? PART 1

A

TRUE CUSHING’S SYNDROME
PSEUDOCUSHING’S SYNDROME - common with:
- depression
- alcoholism
- anorexia nervosa
- obesity

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5
Q

If the screening tests for Cushing’s Disease come back positive, there are 3 possibilities that could cause that.
What are these three possibilities? PART 2

A

EXOGENOUS STEROIDS: found in everyday things such as
- inhalers
- eyedrops
- nasal drops
- skin creams

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6
Q

To remove the possibility of false positives, how do we change the overnight low-dose dexamethasone suppression test?

A
  • Give 4 low-dose tablets a day for 2 days (0.5 mg of dexamethasone six-hourly for 48 hours).
  • No cortisol left in their bloodstream.
  • If cortisol is still detectable then the patient has Cushing’s Syndrome.
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7
Q

After the low-dose dexamethasone suppression test, what different diagnoses can be made?

A

CUSHING’S DISEASE:
- pituitary adenoma

ADRENAL TUMOUR:
- benign/ malignant

ECTOPIC ACTH PRODUCTION:
- benign/ malignant

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8
Q

After the low-dose dexamethasone suppression test, how can we differentiate between the different causes?

A
  • high-dose dexamethasone suppression testing
  • ACTH
  • imaging
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9
Q

Describe the high-dose dexamethasone suppression test.

A
  • High dose of 2 mg of dexamethasone is given every 6 hours for 48 hours.
  • If cortisol suppresses to <50% of baseline, patient has Pituitary-Dependent Cushing’s Disease.
  • If cortisol does not suppress, patient has ectopic ACTH production or adrenal tumour.
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10
Q

What are some laboratory features of cortisol excess?

A
  • hypokalaemia
  • metabolic alkalosis
  • hyperglycaemia
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11
Q

For the CRH test, why would we measure CRH levels and not ACTH levels?

A

ACTH is present in the blood in fragments, making it difficult to measure.

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12
Q

Describe a CRH test.

A
  • 0.1 μg/kg of human CRH is given.
  • Blood assayed for ACTH and cortisol at set times: -15, 0, 15, 30, 45, 60, 90, 120 minutes.
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13
Q

Describe what different results of a CRH test indicate.

A
  • If the ACTH doubles, indicates a normal response.
  • If the ACTH is suppressed, indicates an adrenal tumour.
  • If the ACTH level remains the same, indicates ectopic ACTH production.
  • If there is an exaggerated ACTH response, indicates a pituitary tumour.
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14
Q

Tumours that produce hormones (in this case, ACTH) can be found in different places.
List the different scans/ tests done for each area/ condition to localise the tumour.

A

PITUITARY TUMOUR:
- MRI or IPSS

ADRENAL TUMOUR:
- CT or MRI

ECTOPIC ACTH PRODUCTION:

octreotide scan
ACTH sampling

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15
Q

What would be the treatment for a pituitary tumour?

A
  • Excess cortisol causes patients to be hypertensive, immunosuppressed
  • Risk factors for surgery, so given cortisol production blockers (e.g metyrapone/ ketoconazole).
  • After surgery, patients require placement of other pituitary hormones until normal production resumed.
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16
Q

What would be the treatment for an adrenal tumour?

A
  • Remove the source of an adrenal tumour.
  • Patients will need to have steroid replacement tablets at time of and following surgery.
  • Adrenal tumour suppresses the function of the normal gland
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17
Q

What are some of Addison’s clinical features?

A
  • Weakness
  • Weight loss
  • Postural hypotension
  • Myalgia
  • Hyperpigmentation
  • Hyponatraemia
  • Hyperkalaemia
  • Acidosis
  • Hypercalcaemia
  • Hypoglycaemia
  • Increased urea and creatinine
  • Eosinophilia
18
Q

What are some causes of Addison’s Syndrome?

A
  • Autoimmune diseases
  • Steroid withdrawal
  • Metastases
  • Infiltration (amyloid, haemochromatosis)
  • Waterhouse-Friedrichsen (bleeding in the adrenal glands)
  • Apoplexy (bleeding within internal organs)
  • Infection (fungal, viral)
  • Enzyme defect (congenital adrenal hyperplasia, adrenoleukodystrophy, adrenomyeloneuropathy)
  • Drugs
19
Q

What would be the treatment of Addison’s disease?

A
  • Replace the hormone.
  • Use hydrocortisone; it mimics the diurnal rhythm, with last dose being given at 6 PM.
  • Use fludrocortisone.
20
Q

Describe 21-hydroxylase deficiency (classical) CAH.

A
  • Autosomal recessive and HLA-linked.
  • Patient cannot make aldosterone or cortisol, so build-up of 17-OH and progesterone
  • Excess sex steroids cause virilisation, hirsutism, premature adrenarche, infertility, etc.
  • No aldosterone - hyperkalaemia and hypotension.
21
Q

Describe 11-hydroxylase deficiency (non-classical) CAH.

A
  • Autosomal recessive and HLA-linked.
  • Build-up of 11-deoxycortisol and deoxycorticosterone. Forms excess sex steroids
  • Deoxycorticosterone has a partial action on the aldosterone receptor.
  • So, instead of being hypotensive, patients become hypertensive and hypokalaemic.
22
Q

How do we investigate for enzyme deficiencies in the making of cortisol and aldosterone?

A
  • Synacthen test.
  • No cortisol rise as there are increased 17-OH and progesterone levels.
23
Q

How do we treat enzyme deficiencies in the making of cortisol and aldosterone? PART 1

A
  • 11β- and 21-hydroxylase deficiency uses glucocorticoid therapy (with drugs e.g prednisolone).
  • Acts partially on the mineralocorticoid receptor, providing negative feedback to ACTH.
  • ACTH levels will fall, and the drive to produce testosterone will stop.
24
Q

How do we treat enzyme deficiencies in the making of cortisol and aldosterone? PART 2

A
  • Surgery possible to virilised female genitalia
  • Treat the mother to prevent foetal virilisation.
25
Q

How does aldosterone work with negative feedback?

A
  • No direct negative feedback (no aldosterone receptors on the kidney).
  • Actions of aldosterone (such as increasing extracellular fluid and potassium) provides physiological negative feedback to the kidney to switch off renin production (which would ultimately make aldosterone).
26
Q

Describe the two conditions in which there is an overproduction of aldosterone.

CONDITION 1

A

PRIMARY EXCESS:
- Conn’s Syndrome - mostly caused by tumours
- Caused by bilateral adrenal hyperplasia, steroid-treatable hypertension or an aldosterone-producing adrenal carcinoma.

27
Q

Describe the two conditions in which there is an overproduction of aldosterone.

CONDITION 2 (with hypertension)

A

SECONDARY EXCESS:
- Could be caused by renal artery stenosis
- If the kidney receives less blood, will release more renin to increase blood volume.
- Can also be caused by a renin-secreting tumour or malignant nephrosclerosis.

28
Q

Describe the two conditions in which there is an overproduction of aldosterone.

CONDITION 2 (with normal BP)

A

Associated with congestive heart failure, cirrhosis, nephrotic syndrome and dehydration.

29
Q

How do we treat Conn’s Syndrome?

A
  • removing the primary tumour
  • spironolactone (blocks mineralocorticoid receptors)
  • potassium supplementation
30
Q

Describe phaechromocytoma.

A
  • Tumour of the enterochromaffin cells of the adrenal medulla.
  • Produces adrenaline (noradrenaline, dopamine).
  • 10% are on both adrenal glands, 10% are cancerous, 10% are found outside the adrenal gland and 10% are inherited.
31
Q

What are some symptoms of a phaeochromocytoma?

A
  • sweating
  • anxiety
  • fever
  • paroxysmal hypertension
  • angor amanii (patient’s perception that they are dying)
  • constipation
  • abdominal pain
  • eosinophilia
  • hyperglycaemia
  • hypercalcaemia
32
Q

How would you be able to diagnose a phaeochromocytoma?

A

Look for:
- eosinophilia
- hyperglycaemia
- hypercalcaemia
- raised urinary metabolites, such as metanephrines and catecholamines

Scan using CT and MRI scanning.

33
Q

How would you manage a phaeochromocytoma?

A

Use drugs immediately such as:
- non-competitive α-antagonists (phenoxybenzamine phentolamine)
- non-selective β-blockers (propranolol) (always block α first)

Also:
- fluid resuscitation
- surgery

34
Q

How is renin released?

A

→ Afferent arteriole brings blood in glomerulus and senses blood pressure
→ Macula densa in DCT senses salt
→ JG cells produce renin

35
Q

What happens during hypovolaemia to retain Na+ (mineralocorticoid receptor)?

A

→ The catalytic site of 11 beta hydroxysteroid dehydrogenase 2 has a saturation point which is set higher than normal cortisol
→ Saturation point is lower than extreme cortisol
→ In extreme cortisol the enzyme gets saturated and cortisol can access the receptor
→ so maximal sodium can be retained

36
Q

Why does cortisol not usually bind to the mineralocorticoid receptor?

A

→ Cortisol can bind to the mineralocorticoid receptor
→ 11 beta hydroxysteroid dehydrogenase 2 is part of the mineralocorticoid receptor
→ Cortisol → cortisone by the enzyme (destroyed)
→ Only aldosterone can bind to the receptor

37
Q

How is the electrical balance retained at the mineralocorticoid receptor?

A

→ Na+ retained
→ K+ lost

38
Q

Where does aldosterone bind in the kidney?

A

Mineralcorticoid receptor

39
Q

What does the pituitary gland do when there is high cortisol?

A

Downregulates ACTH

40
Q

What is the cortisol feedback loop?

A

→ CRH is released from the hypothalamus
→ goes to pituitary
→ Stimulates ACTH
→ ACTH stimulates adrenal gland to make cortisol
→ Cortisol inhibits hypothalamus

SGUL - Physiology 1 (68 decks)

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