Addison's & Cushing's Flashcards
What is Cushing’s syndrome?
Set of symptoms caused by excessive cortisol.
What is the most common cause of Cushing’s syndrome?
Cushing’s disease –> pituitary tumour secreting ACTH
Give 2 ACTH dependent causes of Cushing’s syndrome
1) Cushing’s disease (80%)
2) ectopic ACTH production e.g. SCLC
What is the most common cause of ectopic ACTH production?
Small cell lung cancer
Clinical features of Cushing’s?
1) Central obesity & weight gain:
- moon facies
- buffalo hump
- abdominal striae
2) MSK:
- proximal myopathy
- osteopenia & osteoporosis
- avascular necrosis of femoral head
3) Derm:
- hirsutism
- acne & seborrheic dermatitis
- thn skin, easy bruising & poor wound healing
4) Endocrine:
- glucose interolance/T2DM
- menstrual irregularities
- ED
5) Neuropsychiatric:
- depression, anxiety, irritability, emotional lability
- insomnia or hypersomnia
6) CVS:
- HTN
- increased risk of VTE
7) Paediatric:
- growth retardation
- precocious puberty
How can proximal myopathy present in Cushing’s?
Difficulty rising from seated position or climbing stairs
Cause of growth retardation in Cushing’s in children?
Cortisol mediated suppression of GH
Iatrogenic cause of Cushing’s?
Corticosteroid therapy
What is an ACTH independent cause of Cushing’s?
Adrenal adenoma
metabolic disturbance seen in Cushing’s?
Hypokalaemic metabolic alkalosis
What are the 3 most commonly used tests to diagnose Cushing’s?
1) overnight (low-dose) dexamethasone suppression test –> 1st line
2) 24 hr urinary free cortisol
3) bedtime salivary cortisol
result of overnight (low-dose) dexamethasone suppression test in Cushing’s?
patients with Cushing’s syndrome do not have their morning cortisol spike suppressed
After the overnight (low-dose) dexamethasone suppression test has been used to detect Cushing’s syndrome, what test is used next to localise the pathology?
High dose dexamethasone suppression test
Interpretation of results of high dose dex suppression test:
Cortisol not suppressed
ACTH suppressed
Cushing’s syndrome due to other causes (e.g. adrenal adenomas)
Interpretation of results of high dose dex suppression test:
Cortisol suppressed
ACTH suppressed
Cushing’s disease (i.e. pituitary adenoma → ACTH secretion)
Note - high dose dex can suppress ACTH & cortisol in Cushing’s disease
Interpretation of results of high dose dex suppression test:
Cortisol not suppressed
ACTH not suppressed
Ectopic ACTH syndrome
1st line mx of Cushing’s disease?
Trans-sphenoidal removal of pituitary tumour (hypophysectomy)
What is Addison’s disease also known as?
1ary adrenal insufficiency
What is Addison’s disease?
Inadequate production of cortisol AND aldosterone by adrenal cortex.
What is the most common cause of Addison’s?
Autoimmune destruction
How can Addison’s disease cause hyperpigmentation of the skin?
Rise in ACTH (due to loss of adrenal cortex function) –> causes melanocyte-stimulating hormone (MSH) production –> hyperpigmentation.
Clinical features of Addison’s?
- lethargy, weakness, anorexia, N&V, weight loss, ‘salt-craving’
- hyperpigmentation (especially palmar creases), vitiligo, loss of pubic hair in women, hypotension, hypoglycaemia
- hyponatraemia and hyperkalaemia may be seen
- crisis: collapse, shock, pyrexia
Where is hyperpigmentation particularly seen in Addison’s?
Palmar creases
What is the definitive investigation in Addison’s?
ACTH stimulation test (short Synacthen test)
What occurs in the short Synacthen test?
Plasma cortisol is measured before and 30 minutes after giving Synacthen 250ug IM (this mimics ACTH).
If an ACTH stimulation test is not readily available (e.g. in primary care), what investigation can be useful?
Sending a 9 am serum cortisol can be useful:
- > 500 nmol/l makes Addison’s very unlikely
- < 100 nmol/l is definitely abnormal
- 100-500 nmol/l should prompt a ACTH stimulation test to be performed
What electrolyte abnormalities can be seen in Addison’s?
- hyperkalaemia
- hyponatraemia
- hypoglycaemia
- metabolic acidosis
Mx of Addison’s?
Given glucocorticoid & mineralocorticoid replacement therapy:
- hydrocortisone
- fludrocortisone
Mx of steroids in Addison’s during intercurrent illness?
The glucocorticoid dose should be doubled, with the fludrocortisone dose staying the same
Give some complications of Addison’s
1) Adrenal crisis
2) Chronic complications e.g. fatigue weight loss, and electrolyte imbalances
3) Osteoporosis from long term steroid therapy
4) Increased susceptibility to infections
What is an adrenal crisis?
An acute life-threatening condition characterised by severe hypotension, hypoglycemia, and altered mental status
Mx of adrenal crisis?
IV hydrocortisone, fluids & electrolyte correction
