What is adrenal insufficiency?

What is Adrenal Insufficiency?

Adrenal insufficiency is a clinical syndrome characterized by inadequate production of cortisol (and aldosterone in primary cases) from the adrenal cortex, resulting in potentially life-threatening consequences if untreated. 1, 2

Classification and Etiology

Adrenal insufficiency exists in three distinct forms based on the anatomical level of dysfunction:

Primary Adrenal Insufficiency (PAI)

• Direct adrenal gland failure causing deficiency of cortisol, aldosterone, and adrenal androgens 3
• Prevalence: 82-144 per million population 4
• Main causes in adults: Autoimmune adrenalitis (Addison's disease), most common in Western countries 1
• Main causes in children: Genetic disorders, especially congenital adrenal hyperplasia (1 in 15,000 live births) 3
• Other causes: Tuberculosis, fungal infections, bilateral hemorrhage/infarction, metastases, adrenalectomy, high-dose azole antifungals, adrenoleukodystrophy 1, 2

Secondary Adrenal Insufficiency (SAI)

• Pituitary-level dysfunction with isolated cortisol deficiency (aldosterone production preserved) 3
• Prevalence: 150-280 per million population 4
• Causes: Pituitary tumors, hypophysitis (including from immune checkpoint inhibitors), Sheehan's syndrome, pituitary surgery/radiation, trauma, opioid medications 1, 2

Tertiary Adrenal Insufficiency (TAI)

• Hypothalamic-level dysfunction 1
• Most common form overall due to exogenous glucocorticoid therapy causing hypothalamic-pituitary-adrenal axis suppression 1, 3
• Can occur with any route of glucocorticoid administration (oral, inhaled, topical, intranasal, intra-articular) 3

Clinical Presentation

Chronic Symptoms (Non-specific)

• Fatigue: 50-95% of patients 2
• Nausea and vomiting: 20-62% 2
• Anorexia and weight loss: 43-73% 2
• Salt craving (primarily in PAI) 4
• Hyperpigmentation of skin and mucous membranes (PAI only, due to elevated ACTH) 5

Laboratory Abnormalities

• Hyponatremia (common in both PAI and SAI) 4, 5
• Hyperkalemia (primarily in PAI due to aldosterone deficiency) 4, 5
• Hypoglycemia (especially in children and during stress) 4, 5

Adrenal Crisis: The Life-Threatening Emergency

Adrenal crisis is an acute, life-threatening complication occurring at a rate of 6-8 episodes per 100 patient-years, with mortality of 0.5 deaths per 100 patient-years. 6, 4 This represents the most critical outcome concern in adrenal insufficiency management.

Crisis Triggers

• Infections (most common) 6
• Vomiting/diarrhea preventing medication absorption 6
• Surgery, trauma, myocardial infarction 6
• Severe allergic reactions 6

Crisis Manifestations

• Hypotension and shock 2
• Altered mental status 2
• Severe dehydration 5
• Tachycardia 5

Diagnostic Approach

Initial Screening (8 AM measurements)

• Serum cortisol <5 µg/dL (140 nmol/L): Highly suggestive of AI 7, 2
• Serum cortisol 5-10 µg/dL: Indeterminate, requires confirmatory testing 2
• Plasma ACTH: Elevated >2-fold above upper limit in PAI; low or low-normal in SAI/TAI 7, 2
• DHEAS: Low in PAI; low or low-normal in SAI/TAI 7, 2

Confirmatory Testing

The corticotropin (cosyntropin/Synacthen) stimulation test is the diagnostic gold standard for primary adrenal insufficiency. 7

• Standard protocol: 250 µg cosyntropin IV or IM, measure cortisol at 0 and 60 minutes 7
• Note: The 1-µg low-dose test provides no better diagnostic accuracy than the 250-µg test 7
• Caution: May give false-normal results in secondary AI; insulin tolerance test or metyrapone test preferred if SAI strongly suspected 4

Mortality and Morbidity Impact

Mortality is increased 2-fold in Swedish cohorts (risk ratio 2.19 for men, 2.86 for women), with consistently elevated mortality in young patients associated with infection and acute adrenal crisis. 3, 4 This underscores why prevention of adrenal crisis through proper patient education and stress-dose protocols is paramount for improving survival outcomes.

Long-term Quality of Life Concerns

• Impaired physical and mental health components 4
• Potential cardiovascular risk (though data conflicting, may relate to supraphysiological replacement) 4
• Possible bone demineralization (not consistently reported) 4

Critical Clinical Pitfall

Even mild gastrointestinal upset can precipitate adrenal crisis because patients cannot absorb their oral glucocorticoid medication precisely when they need it most. 6 This is why all patients require injectable glucocorticoid emergency kits and explicit instructions on stress dosing.