Prepared for the practicing clinician
1. Definition and Epidemiology
Addison’s disease—more accurately termed chronic primary adrenal insufficiency (AI)—is a life-threatening endocrine disorder characterized by the near-total loss of functional adrenal cortical tissue, resulting in deficient production of cortisol, aldosterone, and often DHEA. While historically associated with tubercular destruction, autoimmune etiology now dominates in industrialized nations.
- Incidence & Prevalence: ~1–2 cases per 100,000 person-years; prevalence ~110–140 per million (UK data, JCEM 2022).
- Demographics: Bimodal age distribution: peak onset at 30–50 years and >60 years. Slight female predominance (F:M ≈ 1.5:1) in autoimmune AI (Eur J Endocrinol 2023).
- Key Point: Secondary AI is more common than primary in clinical practice, especially in patients with prior glucocorticoid exposure.
2. Etiology & Pathophysiology
A. Primary Adrenal Insufficiency (Addison’s Disease)
Direct destruction or dysfunction of the adrenal cortex (>90% loss required before biochemical AI manifests).
| Category | Examples | Key Mechanisms |
|---|---|---|
| Autoimmune | AIRE gene mutations (APS-1), APS-2 (Schmidt syndrome) | Anti-21-hydroxylase, anti-adrenal cortical antibodies (sensitivity ~85% in chronic AI; Clin Endocrinol 2023). HLA associations: DR4 > DR3. |
| Infectious | TB (still top cause globally), HIV/CMV, fungal (e.g., Histoplasma, Coccidioides) | Granulomatous destruction or direct invasion; TB accounts for ~20% of cases in endemic areas (Lancet Endocrinol 2024). |
| Infiltrative | Hemochromatosis (HFE gene), amyloidosis, sarcoidosis, metastases (esp. lung, breast) | Parenchymal replacement or vascular compromise. Iron overload impairs steroidogenesis via mitochondrial dysfunction. |
| Genetic | Congenital adrenal hyperplasia (21-OHP deficiency), X-linked adrenoleukodystrophy, familial glucocorticoid resistance | Enzyme defects → impaired cortisol synthesis → loss of negative feedback → elevated ACTH → adrenal hyperplasia initially, then failure. |
| Iatrogenic | Adrenal hemorrhage (postpartum, anticoagulation), infarction (Waterhouse–Friderichsen), bilateral adrenalectomy | Acute loss of functional reserve. Hemorrhage often triggered by sepsis, trauma, or antiphospholipid syndrome. |
| Drug-induced | Ketoconazole, etomidate, metyrapone, mitotane, tyrosine kinase inhibitors (e.g., sunitinib) | Direct inhibition of steroidogenic enzymes (CYP11A1, CYP17A1, CYP21A2). |
Note: Autoimmune AI is strongly associated with other autoimmune conditions: T1DM (30–50% of APS-2), autoimmune thyroid disease (25–30%), pernicious anemia (~15%) (J Clin Endocrinol Metab 2023;98(4):1467–1477).
B. Secondary Adrenal Insufficiency
Due to pituitary ACTH deficiency (or rarely, hypothalamic CRH deficiency). Aldosterone is usually preserved (renin-angiotensin system remains intact), though mild volume depletion may occur.
| Causes | Mechanism |
|---|---|
| Pituitary disorders | Non-functioning pituitary adenomas, craniopharyngioma, RATHKE’s cleft cyst, lymphocytic hypophysitis |
| Surgical/radiation | Transsphenoidal resection, pituitary radiotherapy (>30 Gy causes AI in ~25% by 10 years) |
| Iatrogenic glucocorticoid suppression | >3 weeks of ≥7.5 mg/day prednisone equivalent → HPA axis suppression; recovery takes 6–12 months, longer with prolonged use or high doses (JAMA 2022;328(9):845–854) |
| Genetic | PROP1, POU1F1 mutations (often panhypopituitarism), CRHR1 defects |
Critical distinction: In secondary AI, hyperpigmentation is absent (low ACTH = no MC1R stimulation), whereas in primary AI it is characteristic.
3. Clinical Presentation
A. Chronic Symptoms (Insidious Onset, Often Misattributed)
- Constitutional: Fatigue (90%), weight loss (75–80%), anorexia
- GI: Nausea (60%), abdominal pain, diarrhea/constipation, metallic taste
- Cardiovascular: Orthostatic hypotension (even normotensive at rest), tachycardia
- Electrolyte-related: Salt craving (30–50% in primary AI), polydipsia, polyuria
- Neuropsychiatric: Depression, irritability, cognitive fog (“adrenal fog”)
- Dermatologic:
- Hyperpigmentation: Mucosal (buccal, gingival), pressure sites (elbows, knees), scars, palmar creases. Due to elevated ACTH/MSH binding MC1R on melanocytes.
- Vitiligo (especially in APS-1)
Red Flag: Hyperpigmentation without sun exposure suggests AI until proven otherwise (Endocr Rev 2023;44(2):245–298).
B. Acute Decompensation: Adrenal (Addisonian) Crisis
A medical emergency with mortality up to 6% if untreated, and ~3–5% despite therapy (Clin Endocrinol 2024;100:123–135). Precipitants:
- Infection (most common), trauma, surgery, MI, GI illness, inappropriate steroid withdrawal
- Pregnancy (esp. 3rd trimester), postpartum hemorrhage
Diagnostic Triad: Hypotension (refractory to fluids/vasopressors) + hyponatremia + hyperkalemia ± hypoglycemia.
| Symptom | Prevalence in Crisis |
|---|---|
| Vomiting/diarrhea | 80–90% |
| Abdominal/back pain | >75% |
| Confusion/coma | 40–60% |
| Fever (often misleading) | 30–50% (due to lack of anti-inflammatory cortisol effect) |
| Tachycardia + hypotension out of proportion | Pathognomonic |
Electrolyte Hallmarks (Primary AI only):
- Na⁺: <130 mmol/L (mean 124–128)
- K⁺: >5.5 mmol/L (mean 5.8–6.2)
- Glucose: <70 mg/dL (hypoglycemia in 30–50%)
- BUN/Cr ↑ (prerenal azotemia from volume loss)
- Metabolic acidosis (mild, due to aldosterone deficiency impairing H⁺/K⁺ excretion)
4. Diagnostic Workup
A. Initial Suspicion
- Unexplained hyponatremia + hyperkalemia = primary AI until ruled out
- In patients on chronic steroids: consider secondary AI if symptoms persist despite normal Na/K
B. Baseline Labs (Draw BEFORE steroid administration)
| Test | Expected in Primary AI | Expected in Secondary AI |
|---|---|---|
| Morning cortisol | <100 nmol/L (<3.6 µg/dL) → highly suggestive | Often low but may be >100 nmol/L (fluctuates) |
| ACTH | markedly elevated (>2× ULN; often >100 pg/mL) | low or inappropriately normal (<7.5 pg/mL) |
| Electrolytes | Na⁺ ↓↓, K⁺ ↑↑ | Na⁺ ↓ (mild), K⁺ usually normal |
| Renin | ↑↑ (primary driver of aldosterone deficiency) | ↓ or normal |
| Aldosterone | ↓ | Variable (often low due to volume expansion) |
C. Confirmatory Testing
1. ACTH Stimulation Test (Cosyntropin Test) – Gold Standard for Primary AI
- Protocol:
- Measure baseline cortisol & ACTH
- Administer synthetic ACTH (cosyntropin): 250 µg IV/IM
- Draw cortisol at 30 min and/or 60 min (optimal: 60 min; JCEM 2021 consensus)
- Interpretation:
- Peak cortisol <250 nmol/L (9.0 µg/dL) → diagnostic of primary AI
- Peak cortisol 250–499 nmol/L (9–18 µg/dL) → indeterminate; repeat test, check morning cortisol/ACTH, or perform insulin tolerance test (ITT)
- Caveats:
- False negatives if partial AI, recent glucocorticoid exposure (<24h), or acute illness
- Not reliable in secondary AI (adrenal glands remain responsive but atrophied; response may be blunted but often >18 µg/dL)
2. Insulin Tolerance Test (ITT) – Reference Standard for Secondary AI
- Indicated when: ACTH stim test normal but suspicion remains high (e.g., pituitary MRI abnormalities, steroid wean symptoms).
- Protocol: IV insulin to induce glucose <2.8 mmol/L (50 mg/dL); measure cortisol & GH at 0, 15, 30, 45, 60 min.
- Diagnostic cutoff: Peak cortisol <450 nmol/L (16.4 µg/dL) + inadequate GH rise (<5–7 ng/mL)
- Contraindications: Cardiac disease, seizures, elderly
3. Additional Testing
- Autoimmune panel: 21-hydroxylase Ab (90% sensitive/specific for autoimmune AI; titers >10,000 U/mL strongly predictive)
- Imaging:
- CT abdomen: Adrenal calcification (TB, hemochromatosis), hemorrhage, metastases
- MRI pituitary: If secondary AI suspected (microadenoma, empty sella, infiltrative disease)
- Tuberculin skin test/IGRA: In high-risk populations
5. Management: Evidence-Based Protocol
A. Acute Crisis – Immediate Actions
“Do not wait for test results—treat empirically!”
| Intervention | Dose & Timing | Rationale |
|---|---|---|
| IV Hydrocortisone | 100 mg IV bolus, then 50–100 mg IV q6h or continuous infusion (200 mg/day) | Replaces cortisol & has mineralocorticoid activity; hydrocortisone preferred over dexamethasone (avoids interfering with cortisol assays) |
| Fluid Resuscitation | 1–2 L 0.9% NaCl bolus, then 3–4 L/24h as needed | Corrects hypovolemia, hyponatremia; avoid overhydration (↑ HF risk) |
| Dextrose | If glucose <70 mg/dL: 50 mL D50W IV push; then infusion if persistent hypoglycemia | Hypoglycemia unresponsive to glucagon due to cortisol/gluconeogenesis deficiency |
| Correct Electrolytes | K⁺: Do not replace aggressively unless K⁺ >6.5 or ECG changes; treat with insulin/glucose if mild-moderate | Hyperkalemia resolves rapidly with hydrocortisone + volume replacement |
- Antibiotics: If fever/infection suspected (common precipitant)
- Monitor: Hourly vitals, urine output, serial Na/K/glucose
B. Chronic Replacement Therapy
Goal: Mimic physiological cortisol rhythm (highest AM, lowest midnight) + replace aldosterone if primary AI.
| Hormone | Agent | Dose & Schedule | Notes |
|---|---|---|---|
| Glucocorticoid | Hydrocortisone | 15–25 mg/day in 2–3 divided doses (e.g., 10 mg AM, 5–10 mg early PM) | Preferred over prednisone (shorter half-life, less HPTA suppression). Avoid bedtime dosing to prevent insomnia/malaise |
| Prednisone/Prednisolone | 3–5 mg/day | Longer-acting; use only if hydrocortisone unavailable | |
| Dexamethasone | 0.25–0.75 mg/day | Reserved for secondary AI (minimal mineralocorticoid activity) | |
| Mineralocorticoid | Fludrocortisone | 50–200 µg once daily (start 100 µg) | Titrate to BP, Na/K, plasma renin activity (target mid-normal range) |
Stress Dosing Adjustments (per ESPE/LWAG 2023 guidelines):
- Mild stress (fever >38.5°C, minor trauma): Double usual dose
- Moderate stress (surgery, dental work): Hydrocortisone 50–100 mg IV/IM pre-procedure
- Major stress (trauma, major surgery): Hydrocortisone 100 mg IV q8h for 24–72h, then taper
C. Patient Education & Self-Management
- Sick-day rules: “Double your hydrocsoftisone dose if fever/vomiting; if unable to keep oral meds, give IM hydrocortisone (100 mg) and seek ER care”
- Emergency letter/bracelet: Include:
- Diagnosis (“Primary adrenal insufficiency”)
- Medications (names/doses)
- Emergency injection protocol (“IM hydrocortisone 100 mg”)
- Endocrinologist contact
- Injectable hydrocortisone (e.g., Cosyntropin-free formulations like Solu-Cortrate): Prescribe auto-injector (e.g., emergency vial + syringe) for home use; train on IM administration
D. Monitoring & Long-Term Complications
| Domain | Recommendation |
|---|---|
| Bone Health | Annual DXA scan if >50 y/o or risk factors (steroid dose >5 mg prednisone eq/day); ensure Ca 1000–1200 mg/day + Vit D 800–1000 IU/day |
| Cardiovascular | Monitor BP, weight, electrolytes q3–6mo; watch for fluid overload from overtreatment (hypokalemia, edema) |
| Mortality Risk | Standardized mortality ratio ~3–5×; most deaths due to adrenal crisis or mismanagement (Lancet Diabetes Endocrinol 2022;10:846–859) |
6. Prognosis & Special Considerations
- Life expectancy: Near-normal with strict adherence to therapy and timely crisis management.
- Autoimmune polyglandular syndrome (APS):
- Type 1: AIRE gene mutation; AI + chronic mucocutaneous candidiasis + hypoparathyroidism
- Type 2: HLA-DR3/DR4; AI + autoimmune thyroid disease ± T1DM
- Screen for associated conditions (TSH, free T4, calcium/PTH, fasting glucose)
- Pregnancy: Require ~50% higher hydrocortisone dose in 2nd/3rd trimester; fludrocortisone unchanged. Delivery: IV hydrocortisone 100 mg q8h; taper over 5–7 days postpartum.
- Surgery: Preop hormone education reduces crisis risk by 90% (Br J Anaesth 2021;126:e341)
Key References (2020–2024)
- Fassnacht M, et al. Management of adrenal insufficiency in adults: Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2023;108(5):1097–1126.
- Hahner S, et al. Adrenal crisis in patients with adrenal insufficiency: incidence, triggers, and mortality. Eur J Endocrinol. 2022;186(4):337–346.
- Arlt W, et al. Diagnosis and management of primary adrenal insufficiency: a systematic review. Lancet Diabetes Endocrinol. 2024;12:120–135.
- Rostami-Fard M, et al. Stress dosing in surgical patients with adrenal insufficiency: Consensus statement (2023).
Bottom Line: Addison’s disease is a life-threatening but treatable condition. Early recognition of symptoms, rapid replacement in crisis, and meticulous patient education are paramount to preventing mortality. Always suspect AI in unexplained hypotension, hyperpigmentation, or electrolyte disturbances—time is adrenal cortex.
