Morning serum cortisol is superior to salivary cortisone and cortisol in predicting normal adrenal function in suspected adrenal insufficiency.

A low index of suspicion for adrenal insufficiency (AI) is necessary to avoid catastrophic missed diagnoses. In consequence most short synacthen tests (SSTs), the first-line investigation in suspected adrenal insufficiency (AI), are normal since they mainly exclude AI. A SST is invasive, labour intensive and requires the patient to attend hospital for the test to be performed under supervision. Consequently, morning serum cortisol cut-offs have been derived to identify patients with an unequivocal pass or fail in a SST, thus reducing the need for SSTs.1.