MON-174 Circadian Misalignment of the 24-H Profiles of Melatonin and Cortisol in Adrenal Insufficiency

Abstract

Patients with adrenal insufficiency (AI), in whom cortisol release is absent, need to be on lifelong replacement therapy. Depending on the modality of glucocorticoid replacement, the resulting 24-h profile of circulating cortisol levels maybe dampened, enhanced, abnormally timed or inconsistent. The 24-h cortisol profile is a major internal synchronizing signal between central and peripheral circadian clocks. Misalignment between central and peripheral clocks has a host of adverse effects, particularly on metabolism and cardiovascular function. Melatonin, normally secreted by the pineal gland exclusively at night and considered a robust marker of central circadian timing, also plays a role as an internal synchronizing signal. Conditions like AI, where the 24-h profile of glucocorticoid levels deviates from normality, could produce misalignment between central and peripheral oscillators.We examined whether AI patients are at higher risk of disturbances of the circadian system. Participants were 13 AI patients (11 females, 2 men; mean age 45.8 yrs old; mean BMI 25.5) and 13 controls (11 females, 2 males; mean age 48.5 yrs old, mean BMI 26.4) matched for age, sex, and BMI. 10 of the AI patients were on hydrocortisone treatment (total dose range: 20 to 40mg/day, number of doses: 1-5 doses/day) and 3 of the AI patients were on prednisone treatment. Cortisol and melatonin were measured over a 24-h period every 30-60 minutes in all patients and controls.The 24-h profile of cortisol was quite variable across patients, dependent on replacement therapy. Those on prednisone had very little detectable cortisol with small peaks that occurred around dosing. Those on hydrocortisone, had multiple peaks across the 24-h cycle dependent on medication regime and dosing. As expected, control subjects had a quiescent period of cortisol release from early evening to mid-sleep (18:00 to 02:00) and a mid-sleep rise in serum cortisol that peaks in the morning and subsequently dissipates across the day. In contrast, AI patients have low levels of cortisol across the entire sleep period, with a sharp morning rise, delayed compared to controls. Unexpectedly, we observed a marked difference in the melatonin profile in AI subjects compared to controls. Indeed, a significant daytime phase of elevated melatonin levels was detected in 7 of the 13 AI patients. The nocturnal elevation in the patients was similar to that observed in controls albeit advanced.In conclusion, the abnormalities of the circadian profile of glucocorticoid levels in AI are associated with an abnormal 24-hr profile of melatonin release, a marker of central circadian function, suggesting that the disruption of the glucocorticoid rhythm may affect central circadian function. It is possible that this circadian dysfunction contributes to the well-known adverse cardio-metabolic outcomes in AI.