Cushing’s Syndrome

30/07/2013 by admin | Endocrine
  1. Clinical condition resulting from prolonged exposure to excessive glucocorticoids – either exogenous administration (commonly) or endogenous hyper-secretion (very rarely).
  2. p/c: M>F (4>1), depression, psychosis, thinned hair, ‘moon face’, ‘buffulo hump’, acne, hirsutism, HTN, IHD, centripetal obesity (‘lemon on a stick’), peptic ulcer, purple striae, dysmenorrhoea, impotence, proximal myopathy, thin skin, easy bruising.
    1. o Differentials: alcoholism or depression!
  3. Ix:
    1. o Diagnosed when 24h urinary free cortisol is increased, midnight cortisol is detectable and 9am cortisol is detectable after 48h of low dose dexamethasone.
    2. o Determine the cause:
    3. o ACTH normal/increased in ACTH-dependant causes
    4. o ACTH low in ACTH-independent causes
    5. o Serum K <3.2mmol/L = ectopic ACTH secretion.
    6. o In ACTH producing (and in turn increasing cortisol) pituitary adenoma (=Cushing’s disease’) there is a 50% suppression of serum cortisol with high dose dexamethasone and no suppression in ectopic disease. Adrenal imaging can be helpful.
    1. o Corticotrophin releasing hormone (CRH): Administer CRH and measure cortisol. Pituitary disease = excessive rise. Ectopic disease = flat response.
    2. o Venous sampling: inferior petrosal sinus sampling to confirm pituitary-dependant disease. Body sampling to locate ectopic source of ACTH.
    3. o Imaging: Cushing’s disease is usually result of microadenoma, which may not be visible on MRI. CT of chest to locate ectopic sources of ACTH.
  1. Mx:
    1. o Drugs: metyrapone (blocks cortisol synthesis), or ketoconazole (inhibits cytochrome p450 enzyme) – lower cortisol levels short term before surgery
    2. o Pituitary adenoma: trans-sphenoidal adenomectomy produces remission in >70%. RT for uncured relapses. Bilateral adrenalectomy produces aggressive pituitary tumour enlargement and hyper-pigmentation as a result of excessive ACTH secretion (=Nelson’s syndrome) unless pituitary RT given.
    3. o Adrenal adenoma: adrenalectomy curative
    4. o Adrenal carcinoma: drug tx with minotane (adrenolytic agent) – surgery not useful.
    5. o Ectopic secretion: surgical removal, medical tx, or adrenalectomy.
  2. Prognosis: Untreated, Cushing’s syndrome has survival of <5years as a result of CVD and infections. 
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