Conventional glucocorticoids (GCs) are unable to mimic physiological cortisol rhythm in adrenal insufficiency (AI), with a significant impact on morbidity and mortality. Possible explanations are supra-physiological doses and impaired cortisol profile. In particular, elevated evening cortisol levels were related to glucose tolerance and insulin sensitivity alterations and visceral obesity. Once-daily-dual-release-hydrocortisone (OD-DR-HC), better reproducing the physiological cortisol profile, reported metabolic improvements in primary AI (PAI) patients switched from immediate release HC, thrice daily, to OD-DR-HC. The aim of this study was to evaluate the cortisol profile and its impact on metabolic outcome in PAI and secondary AI (SAI) patients treated with cortisone acetate twice daily (CA-BID). Eight AI patients on CA-BID underwent full sampling for serum cortisol during 24 h, at 3 h intervals, at baseline and 6 months after the switch to OD-DR-HC. Mean (07001300 h) AUC was 5.76% (P=1) higher, whereas mean (13001900 h), (19000100 h), (13000700 h), and (19000700 h) AUC were 5.92% (P=0.6), 48.69% (P=0.008), 25.08% (P=0.031) and 40.12% (P=0.008) lower with OD-DR-HC than with CA-BID, respectively. Mean total cortisol (19000700 h) AUC was 14.4% lower (P=0.148) with OD-DR-HC than with CA-BID. The afternoon peak with CA-BID was not observed with OD-DR-HC. Moreover, the decrease in (19000100 h) and (01001900 h) AUC was significantly correlated with glucose level decrease (r=0.99; P<0.001) and insulin sensitivity index (ISI) increase 120′ after glucose load (r=−0.99; P<0.001), as well as with waist circumference (r=0.98; P<0.001) and triglycerides level reduction (r=0.95; P<0.001). In conclusion, total 24 h cortisol profile was reduced by 14.4%, providing a higher exposure during the first 6 h in the morning and then significant reductions throughout day and night. OD-DR-HC reduces late afternoon, evening and nocturnal GC overexposure, avoiding the second afternoon peak, suggesting a significant improvement in glucose tolerance, visceral adiposity and lipid profile. Further studies are needed to confirm and extend these preliminary data.