Evaluation and Management of Low Cortisol Levels in Women
Low cortisol levels in women require immediate measurement of paired serum cortisol and plasma ACTH to distinguish primary adrenal insufficiency (PAI) from secondary causes, followed by a 250 µg cosyntropin stimulation test if initial results are equivocal. 1
Diagnostic Approach
Initial Laboratory Assessment
When low cortisol is detected, immediately obtain:
- Paired morning serum cortisol and plasma ACTH - this is the cornerstone diagnostic test 2, 1
- Serum electrolytes - hyponatremia occurs in 90% of PAI cases, though hyperkalaemia is present in only 50% 2
- DHEAS levels - values well below normal for age and sex suggest PAI, though cannot diagnose in isolation 1
Interpretation of Initial Results
Primary Adrenal Insufficiency (PAI) is highly likely when:
- Cortisol <140 nmol/L (5 µg/dL) **AND** ACTH elevated >2-fold above upper limit of normal 1
- In acute illness: cortisol <250 nmol/L with increased ACTH is diagnostic; cortisol <400 nmol/L with increased ACTH raises strong suspicion 2
Secondary adrenal insufficiency is suggested when:
- Low cortisol with low or inappropriately normal ACTH
Confirmatory Testing
The 250 µg cosyntropin (ACTH) stimulation test is the gold standard for confirming PAI 1:
- Administer 250 µg cosyntropin IV or IM
- Measure cortisol at baseline, 30, and 60 minutes
- Peak cortisol <500 nmol/L is diagnostic of PAI 2
- The standard 250 µg dose has 92% sensitivity and is superior to the 1 µg low-dose test 1
Important caveat: The cosyntropin test can be performed at any time of day as results are not affected by diurnal variation 1. However, never delay treatment in suspected acute adrenal crisis to perform diagnostic testing 2.
Establishing Etiology
Once PAI is confirmed, determine the cause:
Measure 21-hydroxylase (anti-adrenal) autoantibodies first - autoimmune adrenalitis is the most common cause 2
If antibodies are negative:
- Order CT imaging of adrenals
- In male patients (or women with virilization), measure very long-chain fatty acids to exclude adrenoleukodystrophy 2
In young women with PAI plus hypoparathyroidism or candidiasis, consider autoimmune polyglandular syndrome type 1 (APS-1) 2
Management
Glucocorticoid Replacement
Most women with PAI should receive 15-25 mg hydrocortisone daily in divided doses 2. The 2016 Endocrine Society guideline systematic review found no mortality or quality of life difference between regimens using ≥30 mg/day versus <30 mg/day of hydrocortisone 1.
Patient Education and Safety
All women with confirmed adrenal insufficiency must:
- Wear medical alert identification jewelry
- Carry a steroid emergency card
- Receive supplies and training for self-injection of parenteral hydrocortisone 2
- Understand stress-dose adjustments for illness
Special Considerations in Women
The evidence does not show sex-specific differences in diagnostic thresholds or treatment regimens for PAI. However, be aware that:
- Exogenous steroids (oral prednisolone, dexamethasone, inhaled fluticasone) confound cortisol interpretation 2
- Cortisol-binding globulin levels (affected by estrogen) can influence total cortisol measurements 1
Critical Pitfalls to Avoid
Do not rely on electrolytes alone - the classic hyponatremia/hyperkalaemia combination is absent in 50% of PAI cases 2
Do not use the CRH test - it has poor sensitivity (76%) for diagnosing adrenal insufficiency despite 96% specificity 3
Do not use dexamethasone for treatment - it is not recommended for critical illness-related corticosteroid insufficiency 4
Do not confuse stress-related hypocortisolism with PAI - conditions like chronic fatigue syndrome, fibromyalgia, and PTSD can show low cortisol without true adrenal insufficiency 5. These represent functional hypocortisolism, not PAI requiring replacement therapy.
In critically ill patients, random cortisol levels and ACTH stimulation test results do not reliably predict mortality and should not solely guide corticosteroid supplementation decisions 6