Endocrinology - Cushing's Flashcards

1
Q

Presentation of Cushing’s

A
Central obesity
Round face
Abdominal striae
Fat pad on upper back (buffalo hump)
Proximal limb muscle wasting

High levels of stress hormone causing:

  • Hypertension
  • Hyperglycaemia (T2DM)
  • Depression
  • Insomnia

Also:

  • Osteoporosis,
  • Easy bruising
  • Poor wound healing
  • Hirsutism

Irregular periods in females

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2
Q

Causes of Cushing’s syndrome

A

Exogenous steroid treatment

Cushing’s disease (pituitary adenoma releasing excessive ACTH)

Adrenal adenoma

Paraneoplastic Cushing’s

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3
Q

What is paraneoplastic Cushing’s?

A

Excess ACTH release from a cancer (which then stimulates excess cortisol release) - most commonly from small cell lung cancer, also carcinoid

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4
Q

Diagnostic test for Cushing’s syndrome

A

Low dose dexamethasone suppression test first
- If abnormal (cortisol not suppressed) - perform high dose dexamethasone suppression test

(24h Urinary free cortisol can be performed as an alternative to Dexa suppression)

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5
Q

How is dexamethasone test done?

A

Dexamethasone given and then cortisol measured after 48h of dexamethasone

Low dose dexamethasone test:

  • Normal - cortisol levels suppressed
  • Abnormal - cortisol levels not suppressed = Cushing’s syndrome
  • If abnormal, perform high-dose dexamethasone test
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6
Q

High dose dexamethasone test result meanings

A

8mg dexamethasone used

In Cushing’s Disease (pituitary adenoma) the pituitary still shows some response to negative feedback and 8mg of dexamethasone is enough to suppress cortisol.

Where there is an adrenal adenoma, cortisol production is independent from the pituitary. Therefore, cortisone is not suppressed however ACTH is suppressed due to negative feedback on the hypothalamus and pituitary gland.

Where there is 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.

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7
Q

High dose dexamethasone suppression test shows suppressed cortisol and ACTH…

A

Cushing’s disease (Pituitary adenoma)

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8
Q

High dose dexamethasone suppression test shows not suppressed cortisol but ACTH is suppressed

A

Adrenal adenoma

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9
Q

High dose dexamethasone suppression test shows neither cortisol or ACTH are suppressed

A

Ectopic ACTH secretion e.g. small cell lung cancer

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10
Q

Other investigations in suspected Cushing’s syndrome

A

BP

FBC - raised white cells) and electrolytes (potassium may be low if aldosterone is also secreted by an adrenal adenoma)

MRI brain (for pituitary adenoma)

CT Thorax (small cell lung cancer)

Abdominal CT (adrenal tumours)

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11
Q

Treatment of Cushing’s syndrome

A

To surgically remove the underlying tumour cause

Trans-sphenoidal (through the nose) removal of pituitary adenoma

Surgical removal of adrenal tumour

Surgical removal of tumour producing ectopic ACTH

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12
Q

If surgical removal is not possible…

A

If surgical removal of the cause is not possible another option is to remove both adrenal glands and give the patient replacement steroid hormones for life.

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