Cushing syndrome

Question 1

Cortisol

Answer 1

Stress hormone
Maintain BP
-regulate alpha 1 arteriole receptors – more responsive to Epi/NE
-w/o may have difficulty maintaining BP

Increase energy:
Elevated gluconeogenesis -> DM
Elevated lipolysis
Elevated proteolysis

Suppresses immune system – temporarily move WBC into blood
Suppresses inflammation
Decreases bone formation -> osteoporosis

Question 2

Glucocorticoids

Answer 2

Hydrocortisone
Prednisone

IV forms:
Prednisolone
Methyl prednisolone

Dexamethasone – not picked up on labs

Topical: triamcinolone

Inhaled:
Beclomethasone
Fluticasone

Inhibit COX and phospholipase A2

Chronic use -> cushing sn, DM, osteoporosis

Increased risk glaucoma, peptic ulcers, insomnia, agitation, psychosis

Can cause secondary adrenal insufficiency d/t negative feedback on ACTH -> atrophy of adrenal cortex

Question 3

Causes of Cushing syndrome

Answer 3

1. Iatrogenic exogenous corticosteroid therapy
2. cushing dz – pituitary adenoma -> increased ACTH

non-pituitary tumor or cancer producing ectopic ACTH – small cell lung cancer

Adrenal overproduction of cortisol – adrenal adenoma

Question 4

Dexamethasone suppression test

Answer 4

Low dose 1 mg, high dose 8 mg

Normal: low dose -> decreased cortisol – proper negative feedback

ACTH-producing pituitary tumor (only tumor suppressable w/ high dose): low dose: elevated cortisol; high dose: decreased cortisol

Ectopic ACTH production: low dose: elevated cortisol, high dose: elevated cortisol

• lung CA – no feedback mechanism
• high ACTH

Cortisol-producing tumor:
Low and high dose: elevated cortisol
-low ACTH