The cortisol awakening response is blunted in patients with active Cushing's disease

Cortisol awakening response (CAR) is a rapid increase of cortisol levels within 30-45 min after awakening.

This study evaluates CAR compared with cortisol circadian rhythm in active and in remission Cushing's disease (CD).

We evaluated healthy controls (HC, n=19), obese (OB, n=10), in remission (n=08), and active CD patients (n=10). Salivary free cortisol (SF) was determined at 0800, 1100, 1700, 2000, and 2300 h on the first day. CAR was obtained the next morning immediately upon awakening and at 15, 30, 45, and 60-min post-wake up.

We observed differences in SF levels throughout the day in HC, OB, and in remission CD (ANOVA P=0.0001) but not in active CD (P=0.2). We demonstrated SF increment after awakening in HC, OB, and in remission CD (ANOVA P=0.007), with no effect of time on SF in active CD. The relative increment of SF obtained at the peak after awakening (CARi%) in the active CD (67±57%) was lower than in HC (154±107%), OB (240±188%), and in remission CD (186±184%) patients (P=0.009). There was a negative correlation between the SF at awakening and the CARi% in HC (r=-0.8), OB (r=-0.78), and in remission CD (r=-0.74) but not in active CD (r=-0.35; P=0.31).

This study originally described a blunted CAR in active CD in contrast to its presence in HC, OB, and in remission CD. This subtle dysfunction of the hypothalamus-pituitary-adrenal axis may represent a distinct and additional physiopathological phenomenon superimposing the dysregulated cortisol circadian rhythm in this disease.