Residual Adrenal Function in Addison's Disease

Addison's disease is an autoimmune disease characterized by inadequate secretion of cortisol and aldosteron by adrenal cortex as a consequence of progressive destruction of the adrenal gland. The absence of specific signs and symptoms could delay the diagnosis and treatment. Considering the importance of these two hormones, a not adequate treatment can result in Addisonian crisis and even be a cause of increased mortality.

Actually, diagnosis is based either on low basal cortisol levels or cortisol levels after Synacthen test (250 mcg) < 500 nmol/L.

Adrenal insufficiency (AI) is most of the time the inevitable end result of the autoimmune process, but some cases of partial recovery of adrenal function in a patient with autoimmune Addison's disease have been described.

Recent evidence shows that 5-30% of Addison's patients, also after many years of disease, maintain a residual endogenous corticosteroid production thanks to a partial adrenal cortex functionality, known as residual adrenal function (RAF).

Indeed, some studies show how the 3-15% of patients have detectable cortisol at Synacthen 250 mcg test, demonstrating that in one third of patients with long-standing disease, some RAF was still present.