Addison’s Disease USMLE Notes & Mnemonics contains all the high-yield points you need to know.
- Addison’s Disease: A condition characterized by insufficient production of cortisol and often aldosterone due to adrenal cortex dysfunction.
Etiology:
- Primary Adrenal Insufficiency: Direct adrenal gland damage.
- Autoimmune: Most common cause in developed countries.
- Infections: TB, HIV, fungal infections.
- Other Causes: Hemorrhage, metastasis, adrenalectomy.
- Secondary Adrenal Insufficiency: Due to lack of ACTH production from the pituitary.
Pathophysiology:
- Cortisol Deficiency: Leads to hypoglycemia, fatigue, and stress intolerance.
- Aldosterone Deficiency: Causes hyponatremia, hyperkalemia, volume depletion, hypotension.
- ACTH Elevation (in primary): Results in hyperpigmentation due to melanocyte-stimulating hormone (MSH) increase.
Clinical Features:
- Chronic Fatigue
- Muscle Weakness
- Weight Loss
- Hyperpigmentation: Especially in sun-exposed areas, creases, and scars. (Ref)
- Hypotension
- Salt Craving
- Gastrointestinal Symptoms: Nausea, vomiting, diarrhea.
Diagnosis:
- Baseline Cortisol and ACTH Levels: Low cortisol with high ACTH suggests primary adrenal insufficiency.
- ACTH (Cosyntropin) Stimulation Test: Lack of cortisol response confirms Addison’s disease.
- Electrolytes: Hyponatremia, hyperkalemia.
- Autoantibody Testing: For autoimmune adrenalitis.
Management:
- Glucocorticoid Replacement: Hydrocortisone or prednisone.
- Mineralocorticoid Replacement: Fludrocortisone for aldosterone deficiency.
- Manage Acute Adrenal Crisis: IV fluids, IV glucocorticoids, correction of electrolyte imbalances.
High-Yield Mnemonic: “ADDISON”
- Autoimmune destruction
- Deficiency of cortisol
- Darkening of skin (hyperpigmentation)
- Inadequate aldosterone
- Salt craving
- Orthostatic hypotension
- Nausea, vomiting, and weight loss
Chart: Addison’s Disease vs Secondary Adrenal Insufficiency
| Feature | Addison’s Disease (Primary) | Secondary Adrenal Insufficiency |
|---|---|---|
| ACTH Levels | High | Low or normal |
| Aldosterone Deficiency | Present | Absent (no hyperkalemia) |
| Hyperpigmentation | Present | Absent |
| Cause | Adrenal destruction | Pituitary or hypothalamic dysfunction |
Note: For the USMLE, it is crucial to differentiate between primary and secondary adrenal insufficiency based on clinical presentation, laboratory findings, and response to ACTH stimulation test. Recognizing an adrenal crisis as a life-threatening emergency requiring immediate treatment is also essential.
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