THU611 Circadian Misalignment Of Melatonin Secretion In Adrenal Insufficiency (AI)
Authors: Darji Monika , Pannain Silvana , Sam Susan , Van Cauter Eve , Hanlon Erin C 
Published: October 2023

Disclosure: M. Darji: None. S. Pannain: None. S. Sam: None. E. Van Cauter: None. E.C. Hanlon: None.

Background: Despite glucocorticoid replacement, the mortality risk of AI remains markedly elevated. Under normal conditions, the circadian rhythm of endogenous cortisol levels is a major internal synchronizing signal between central and peripheral circadian clocks. There is increasing evidence indicating that circadian misalignment has a host of adverse effects, including increased cardio-metabolic risk. The present study aimed to assess circadian function in AI patients, as compared to individually-matched healthy subjects, under controlled laboratory conditions. The 24-h profile of melatonin, normally secreted exclusively at night, was used as the marker of central circadian timing. The 24-h profile of leptin was used as a marker of peripheral circadian function. Methods: Plasma cortisol, melatonin, and leptin were measured over a 24-h period every 30-60 minutes under controlled light-dark, sleep-wake and dietary conditions. A best-fit curve was calculated for each individual hormonal profile using a locally weighted nonlinear regression procedure with a window of 4 hours. The peak and the nadir were defined as the maximum and minimum of the best-fit curve, respectively. The amplitude was defined as half of the difference between the peak and the nadir. Sleep was polygraphically recorded. During daytime hours, the participants completed validated questionnaires assessing Vigor, Mood and Sleepiness. Results: Complete data sets were obtained in 15 AI patients (12 women; age: 47.9 ±12.5 years, BMI: 26.6 ± 12.5 kg/m2; mean ± SD). Twelve AI patients were on hydrocortisone treatment (total dose range: 20 to 40mg/day, number of doses: 1-5 /day) and 3 were on prednisone treatment. Controls (n=15, 12 women) were aged 48.5 ±14.5 years with BMI of 26.5 ± 5.4 kg/m2. The amplitude of the cortisol profile was wider in AI patients, relative to controls, with a higher morning peak and an extended and lower nocturnal nadir. Unexpectedly, we observed a marked difference in the melatonin profile in AI patients as compared to controls. A daytime phase of elevated melatonin levels, culminating prior to lights off while the patients were awake, was detected in 9 of the 15 AI patients. The nocturnal elevation persisted with a similar amplitude to that observed in controls but was advanced by 1-2 hours. The 24-h leptin profile was similar in the two groups. The presence of a daytime melatonin peak in AI patients was associated with lower ratings of vigor and mood, and higher ratings of sleepiness. Conclusion: Glucocorticoid treatment to replace the endogenous levels and circadian rhythmicity of cortisol in AI may impact central circadian timing, resulting in daytime, in addition to nighttime, release of melatonin. This finding suggests that exogenous cortisol replacement that does not mimic a normal 24-h rhythm, may cause central circadian dysfunction and contribute to alterations in mood, vigor and sleepiness.

Presentation: Thursday, June 15, 2023