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Endocrine > Cushing's > Flashcards

Cushing's Flashcards

1
Q

What causes of Cushing’s syndrome are more common: endogenous or exogenous

A

exogenous causes of Cushing’s syndrome (e.g. glucocorticoid therapy) are far more common than endogenous ones.

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2
Q

ACTH dependent causes of Cushing’s

A

ACTH dependent causes

  • Cushing’s disease (80%): pituitary tumour secreting ACTH producing adrenal hyperplasia
  • ectopic ACTH production (5-10%): e.g. small cell lung cancer
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3
Q

ACTH independent causes of Cushing’s

A

ACTH independent causes

  • iatrogenic: steroids
  • adrenal adenoma (5-10%)
  • adrenal carcinoma (rare)
  • Carney complex: syndrome including cardiac myxoma
  • micronodular adrenal dysplasia (very rare)
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4
Q

What’s Carney complex?

A

Carney complex: syndrome including cardiac myxoma

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5
Q

What’s Pseudo - Cushing’s? + cause

A

Pseudo-Cushing’s

  • mimics Cushing’s
  • often due to alcohol excess or severe depression
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6
Q

What test results may be seen in Pseudo-Cushing’s?

What test is used to differentiate?

A
  • causes false positive dexamethasone suppression test or 24 hr urinary free cortisol
  • insulin stress test may be used to differentiate
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7
Q

What electrolyte abnormality can be seen along with impaired glucose tolerance in Cushing’s?

A

hypokalemic metabolic alkalosis

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8
Q

What metabolic abnormality is associated with Cushing’s linked to ectopic ACTH secretion in small cell lung ca?

A

very low potassium

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9
Q

Test to differentiate between Cushing’s and pseudo-Cushing

A

Insulin stress test

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10
Q

Two tests to confirm Cushing

A
  • overnight dexamethasone suppression test (most sensitive)
  • 24 hr urinary free cortisol
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11
Q

Cushing’s features (associated with limbs and obesity)

A

Round in the middle with thin limbs:

  • Round “moon” face
  • Central Obesity
  • Abdominal striae
  • Buffalo Hump (fat pad on upper back)
  • Proximal limb muscle wasting
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12
Q

Features of Cushing associated with high levels of stress hormone

A
  • hypertension
  • insomnia
  • depression
  • cardiac hypertrophy
  • hyperglycaemia (T2DM)
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13
Q

Extra effects of Cushing (3)

A
  • easy bruising
  • poor wound healing
  • osteoporosis
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14
Q

Times of dexamethasone test

What’s the aim

A
  • To perform the test the patient takes a dose of dexamethasone (a synthetic glucocorticoid steroid) at night (i.e. 10pm) and their cortisol and ACTH is measured in the morning (i.e. 9am)
  • The intention is the find out whether the dexamethasone suppresses their normal morning spike of cortisol.
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15
Q

What result on dexamethasone suppression test would exclude Cushing’s?

A

Low CRH (pituitary) and ACTH (cortisol production suppressed)

* this is due to negative feedback: dexamethasone suppressing production of CRH by hypothalamus and therefore ACTH from pituitary is suppressed as well

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16
Q

What are the doses of dexamethasone used in low and high dexamethasone supression tests?

A

Low dexamethasone: 1 mg

High: 8 mg

17
Q

What if cortisol levels are not suppressed with low dexamethasone tests?

A

That implies Cushing’s syndrome -> we do high dexamethasone suppression test to localise

18
Q

What results of the dexamethasone suppression test would be seen in Cushing’s Disease?

A

Cushing’s disease = pituitary adenoma

  • still some negative feedback - on 8mg dexamethasone
19
Q

Results on dexamethasone suppression test in adrenal adenoma

A
  • Cortisol production is independent from the -> cortisone is not suppressed
  • ACTH is suppressed due to negative feedback on the hypothalamus and pituitary gland
20
Q

Results on dexamethasone suppression test in ectopic ACTH production

A
  • ectopic ACTH* = e.g. from a small cell lung cancer
  • neither cortisol or ACTH will be suppressed because the ACTH production is independent of the hypothalamus or pituitary gland
21
Q

Other investigations in Cushing’s disease

A
  • 24 hour urinary free cortisol can be used as an alternative to the dexamethasone suppression test (does not indicate the location)
  • FBC (raised white cells)
  • electrolytes (potassium may be low if aldosterone is also secreted by an adrenal adenoma)
  • MRI brain for pituitary adenoma
  • Chest CT for small cell lung cancer
  • Abdominal CT for adrenal tumours
22
Q

What’s the main treatment for Cushing’s?

A

The main treatment is to remove the underlying cause (surgically remove the tumour)

23
Q

Surgeries in Cushing’s disease (3)

*depending on location

A
  • Trans-sphenoidal (through the nose) removal of pituitary adenoma
  • Surgical removal of adrenal tumour
  • Surgical removal of tumour producing ectopic ACTH
24
Q

What if surgical options to remove the cause of Cushing’s are not possible?

A
  • remove both adrenal glands
  • give the patient replacement steroid hormones for life
25
Q

What procedure is used to determine on which side of pituitary the tumour is located?

A

Petrosal sampling

Endocrine (11 decks)

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