Cushing's Syndrome - MADE SIMPLE

Source:  Cushing's Syndrome - MADE SIMPLE    Tag:  nodular adrenal hyperplasia


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Cushing syndrome is defined as:  Increase cortisol due to a variety of causes.
  • Exogenous (iatrogenic) steroids—#1 cause leading to “Decrease CRH & ACTH” due to negative feedback of cortisol (steroids)
  • Endogenous

Endogenous causes:

  • Cushing’s disease (70%)—due to ACTH secretion from pituitary adenoma; “Increase ACTH
  • Ectopic ACTH ”paraneolplastic tumor” (15%)—from non-pituitary tissue making ACTH (e.g., small cell lung cancer, bronchial carcinoids); “Increase ACTH
  • Adrenal adenoma (15%), carcinomanodular adrenal hyperplasia; “Decrease ACTH” due to negative feedback.


Findings:
  • Hypertension,
  • Weight gain,
  • Moon facies,
  • Truncal obesity,
  • Buffalo hump,
  • Hyperglycemia (insulin resistance),
  • Skin changes (thinning, striae),
  • Osteoporosis,
  • Amenorrhea,
  • Immune suppression
  • Cushing syndrome is also a common cause of anovulation.


Dexamethasone (synthetic glucocorticoid) suppression test:

  • Healthy: Decrease cortisol after low dose.
  • ACTH-producing pituitary tumor: Increase cortisol after low dose; Decrease cortisol after high dose.
  • Ectopic ACTH-producing tumor (e.g., small cell carcinoma): Increase cortisol after low and high dose.
  • Cortisol-producing tumorIncrease cortisol after low and high dose.


Causes and Differentiation:





Mnemonic: 

Click on the image to enlarge.


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CORTISOL:

Source:
  • Adrenal zona fasciculata.
Function:
  1. Maintains Blood pressure (permissive effect with epinephrine—upregulates alpha1 receptors on arterioles)
  2. Decrease Bone formation
  3. Anti-Inflammatory
  4. Decrease Immune function
  5. Increase Gluconeogenesislipolysisproteolysis
Regulation:
  • CRH (hypothalamus) stimulates ACTH release from the pituitary gland, causing cortisol production in adrenal zona fasciculata.
  • Excess cortisol –> Decreases CRH, ACTH, and cortisol secretion.