Primary adrenal insufficiency (Addison disease) results from autoimmune destruction, infections (historically tuberculosis), hemorrhage, or infiltrative diseases of the adrenal glands, leading to high ACTH levels and mineralocorticoid deficiency. Secondary adrenal insufficiency arises from inadequate ACTH secretion by the pituitary, with preserved or reduced aldosterone production. Tertiary forms stem from hypothalamic impairment. Drug-induced suppression of the hypothalamic-pituitary-adrenal axis can cause secondary or tertiary forms.
Patients often experience fatigue, weakness, weight loss, abdominal pain, nausea, vomiting, and low blood pressure. In primary disease, hyperpigmentation of the skin and mucous membranes may occur due to elevated ACTH. Electrolyte disturbances such as hyponatremia and hyperkalemia, dehydration, and hypoglycemia can be present, especially in primary disease.
Diagnostic assessment includes morning cortisol, plasma ACTH, and ACTH stimulation testing. A blunted or absent cortisol response to cosyntropin supports insufficiency. Elevated ACTH with low aldosterone and electrolyte abnormalities suggests primary disease, whereas low or normal ACTH points to secondary or tertiary causes. Imaging may be used to evaluate structural etiologies in selected cases.
Glucocorticoid replacement (commonly hydrocortisone) is required to substitute deficient cortisol; mineralocorticoid replacement (fludrocortisone) is often needed in primary disease. During illness, stress, or surgery, patients require higher-dose, stress-related steroid supplementation. Adrenal crisis is life-threatening and requires prompt intravenous fluids, hydrocortisone administration, and correction of electrolyte and glucose abnormalities. Lifelong management and education on stress dosing are essential.