From the Research
Central adrenal insufficiency is characterized by low serum cortisol levels, inappropriately low or normal ACTH levels, and often normal aldosterone and renin levels, with mild hyponatremia and hypoglycemia possible. The diagnosis of central adrenal insufficiency can be challenging due to its nonspecific symptoms, but certain laboratory abnormalities are key to its identification.
- Low serum cortisol levels, particularly during times of stress or in the morning, are a hallmark of the condition, as cortisol levels should be at their peak during these times 1.
- ACTH (adrenocorticotropic hormone) levels are inappropriately low or normal, rather than elevated, which distinguishes central adrenal insufficiency from primary adrenal insufficiency where ACTH is typically high 2, 1.
- Patients with central adrenal insufficiency usually have normal aldosterone and renin levels because the renin-angiotensin-aldosterone system remains intact, unlike in primary adrenal insufficiency where aldosterone is often low 2, 1.
- Electrolyte abnormalities are less common than in primary adrenal insufficiency, though mild hyponatremia may occur, and hypoglycemia can be present, especially during fasting or stress, due to inadequate cortisol-mediated gluconeogenesis 2, 1.
- Diagnosis is confirmed with dynamic testing, particularly the insulin tolerance test or the more commonly used cosyntropin stimulation test, which shows an inadequate cortisol response to ACTH stimulation 3, 1.
- Morning cortisol levels below 3 μg/dL strongly suggest adrenal insufficiency, while values above 15 μg/dL generally exclude the diagnosis, and basal cortisol levels ≤100 and ≥450 nmol/L have high diagnostic accuracy for ruling in or out adrenal insufficiency, respectively 4.