Whether consideration of post-surgical adrenal insufficiency in conjunction with other parameters predicts recurrence better than post-surgical cortisol levels alone is also unclear. In one study, recovery from transient post-surgical adrenal insufficiency (2–34 months) followed by normalized hypothalamus–pituitary–adrenal (HPA) axis function predicted a low recurrence rate (13 %), whereas lack of a diurnal rhythm of cortisol secretion after normalized adrenal function predicted significantly higher recurrence rates (50–65 %) [28]. In contrast, results from another study showed that the time to complete normalization of the HPA axis following surgery was the only positive indicator of recurrence; all patients who recurred had recovered their HPA axis function within 3 years of surgery [29]. Yet others report that a lower risk of recurrence was associated with normal cortisol suppression by low-dose dexamethasone [30, 31]. Similarly, high levels of ACTH in response to corticotrophin-releasing hormone (CRH) or desmopressin stimulation better predicted relapse than post-operative serum cortisol levels alone [32–36]. As such, it is plausible that patients with subtle abnormalities of the HPA axis following surgery may be at risk for persistent or recurrent hypercortisolemia, which may be mild yet insidious.