Adrenal Insufficiency
Adrenal insufficiency occurs when the adrenal glands do not produce enough cortisol, the hormone central to stress response, blood pressure, glucose regulation, and inflammation. Primary insufficiency (Addison's disease) is an adrenal gland problem; secondary insufficiency results from inadequate ACTH from the pituitary, most commonly caused by chronic corticosteroid use.
Symptoms
Profound fatigue, muscle weakness, unintentional weight loss, decreased appetite, nausea, abdominal discomfort, postural dizziness, salt craving, low blood pressure, and -- in primary Addison's disease -- hyperpigmentation of skin creases, scars, and mucous membranes.
Causes and risk
Autoimmune adrenalitis causes 80% of primary cases. Other causes include tuberculosis, HIV, fungal infections, metastatic cancer, bilateral adrenal hemorrhage, and adrenoleukodystrophy. Secondary insufficiency most commonly results from long-term exogenous steroid suppression of the HPA axis.
How it is evaluated
An 8 AM cortisol below 3 mcg/dL is highly suggestive. The ACTH stimulation test (250 mcg cosyntropin, cortisol at 30 and 60 minutes) is the gold-standard confirmatory test. ACTH level distinguishes primary from secondary. Adrenal antibodies confirm autoimmune Addison's. CT imaging evaluates adrenal structure.
Treatment
Hydrocortisone (or prednisolone) replaces cortisol on a two- to three-times-daily dosing schedule mimicking the diurnal rhythm. Fludrocortisone replaces aldosterone in primary insufficiency. Sick-day rules -- doubling the dose for fever or illness -- and medic-alert identification are essential safety measures.