A comparison of 6 am v/s 9am basal serum cortisol

IJEM journal presentation on a comparison of 6 am versus 9 am serum cortisol - Effect of sunrise across different regions of INDIA

1. A Comparison of 06:00 AM Versus 09:00 AM Serum Cortisol as a Basal Morning Cortisol in Guwahati, Assam: A Pilot Study Indian Journal of Endocrinology and Metabolism Published Volume 28 ¦ Issue 3 ¦ May-June 2024 PRESENTED BY Dr. Khushboo Garg DM Resident R.N.T Medical College Udaipur

2. OVERVIEW OF PRESENATION Introduction Journal proper Aim and objective Materials and methods Results Limitations Take home message

3. INTRODUCTIO N Cortisol, a glucocorticoid hormone, is critical for normal body homeostasis and its secretion is regulated by the hypothalamic‑pituitary‑adrenal (HPA) axis . Cortisol secretion is regulated by the circadian rhythm, which is influenced by external cues called zeitgebers , such as light‑dark cycle, awakening and social cues . Light, in particular plays a crucial role in the entrainment of the circadian rhythm. Normal secretory patterns include the circadian rhythm regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus, which responds to the ambient light‑dark cycle. Hence, changing daylight periods with changing seasons could potentially affect the timing of cortisol secretion . .

4. There is also an ultradian rhythm with pulses of cortisol secretion occurring hourly . An ultradian rhythm overlies the circadian and appears to be driven by an oscillator created between the secretion of ACTH, the short delay in response at the adrenal, and the subsequent negative feedback by cortisol at the hypothalamus and pituitary .

5. Circadian System Rhythm Descriptions Circadian Rhythm A biological process that exhibits an endogenous, entrainable oscillation of ~24 h. Ultradian Rhythm A recurrent cycle or period with a period significantly shorter than 24 h—e.g., a 2-h rhythm would exhibit 12 cycles within a circadian (24-h) rhythm. Diurnal Rhythm An oscillation synchronized with the day/night cycle that repeats itself with a 24-h period. The rhythm does not have to persist when time cues (e.g., light) are absent.

6. E. Van Cauter and J. Aschoff : Endocrine and other biological rhythms. In: DeGroot LJ, ed.  Endocrinology.  Vol 3. WB Saunders; Philadelphia, PA: 1989; 2658–2705 Endocr Rev , Volume 38, Issue 1, 1 February 2017, Pages 3–45 , Schematic conceptual representation of the mammalian circadian system .

7. Anatomic organization of Mammalian Circadian Clock

8. Molecular organization of Mammalian Circadian Clock Harrison text book of internal medicine 21 st edition

9. Endocr Rev , Volume 38, Issue 1, 1 February 2017, Pages 3–45 Schematic representation of the control of the circadian rhythmicity of glucocorticoid release in mammals .

10. A temporal pattern of episodic secretion was recognized, and the 24-hr sleep-wake cycle could be divided into 4 unequal temporal phases:  Phase 1. A 6-hr period of “ minimal secretory activity ” (4 hr before and 2 hr after lights out);  Phase 2. A 3-hr period called “preliminary nocturnal secretory episode” (3rd to 5th hr of sleep);  Phase 3. A 4-hr period, the “ main secretory phase” (6, 7, 8 hr of sleep and 1st hr after awakening); and  Phase 4. The 11 hr of “intermittent waking secretory activity.”

11. Harrison text book of internal medicine 21 st edition COSINOR static model represents acrophase , amplitudes and MESOR ( Midline Estimating Statistic of Rhythm)

12. A drenal glucocorticoid secretion, which is driven by ACTH , follows a parallel diurnal rhythm. The circadian ACTH rhythm appears to be mediated principally by an increased ACTH pulse amplitude occurring between 5 and 9 am but also by a reduction in ACTH pulse frequency occurring between 6 pm and midnight. The average ACTH pulse frequency is higher in normal adult men compared with women (18 vs 10 pulses/24 hours, respectively) Circadian and pulsatile secretion of adrenocorticotropic hormone (ACTH) and cortisol in a normal subject William textbook of Endocrinology 14ed ACTH secretion

13. ROLE OF BASAL CORTISOL IN DIAGNOSIS OF ADRENAL INSUFFICIENCY As per the recommended international guidelines, sampling for morning basal cortisol is performed between 08:00 to 09:00 AM. A basal cortisol concentration cut‑off threshold of <140 nmol/L (5 μg /dL), measured in the morning, indicates the possibility of adrenal insufficiency.

14. Endocrine Society Guidelines 2016 (JCEM) If a corticotropin stimulation test is not feasible, morning (6-10 am) cortisol <140 nmol/L (5 ug/dL) in combination with ACTH (> 2- fold the upper limit of the reference range) as a preliminary test suggestive of AI (until confirmatory testing with corticotropin stimulation is available). Simultaneous measurement of plasma renin and aldosterone in PAI to determine the presence of mineralocorticoid deficiency. T he short corticotropin stimulation test is recommended as the gold standard diagnostic test to establish the diagnosis of adrenal insufficiency. Diagnosis of Adrenal Insufficiency

15. The standard dose iv corticotropin stimulation (30 or 60 min) test 250 mcg for adults and children > 2 y of age 15 mcg/kg for infants 125 mcg for children < 2 y of age Peak cortisol levels below 500 nmol/L (18 ug/dL) (assay dependent) at 30 or 60 minutes indicate adrenal insufficiency. C orticotropin Stimulation Test Endocrine Society Guidelines 2016 (JCEM)

16. Endocrine Society Guidelines 2016 (JCEM) T he etiology of PAI should be determined in all patients with confirmed diagnosis.

17. SUNRISE EFFET ON BASAL CORTISOL ACROSS DIFFERENT REGIONS OF INDIA The Republic of India spans two geographical time zones but uses a one time zone called India Standard Time (IST), which corresponds to Coordinated Universal Time (UTC) +05:30 throughout the entire country. As sunrise in North East India, including Assam, is approximately 1.5 hours earlier than in Western India, occurring around 06:00 AM in December and January and 04:30 AM in June and July , interpreting a morning cortisol sample taken at 09:00 AM may be misleading, leading to an erroneous diagnosis of adrenal insufficiency.

18. JOURNAL PROPER Indian Journal of Endocrinology and Metabolism

19. OBJECTIVE Aim of this study is to compare the basal serum cortisol levels between 06:00 AM and 09:00 AM in Guwahati, Assam, where sunrise occurs earlier compared with the western part of our country .

20. MATERIALS AND METHODS STUDY DESIGN This was a cross‑sectional study conducted from December 2022 to June 2023 in a tertiary care hospital in Guwahati, Assam. The study group consisted of 25 participants with normal body mass index (BMI) without any comorbidities

21. INCLUSION CRITERIA Normal healthy adults aged between 18 and 40 years were included in the study .

22. EXCLUSION CRITERIA Patients with any endocrine disease, on steroid therapy, pregnant women, any chronic illness, night shift workers, P atients with any psychiatric disorders or on psychiatric medications, P atients on drugs known to affect cortisol metabolism or a family history of pituitary or adrenal tumors

23. STUDY PROCEDURE A detailed clinical history and systemic examination of the study participants were recorded. After fulfilling the inclusion and exclusion criteria, samples for 06:00 AM serum cortisol and 09:00 AM serum cortisol were collected after an overnight fast of 10 hours in both January and June 2023 of the same 25 participants. Serum cortisol was measured using the Elecsys Cortisol II assay in the cobase 411 analyzer, Roche Diagnostics. The inter‑ and intra‑assay coefficient of variation was <4%.

24. STASTICAL ANALYSIS USED IN THIS STUDY The statistical analysis was performed using the latest version of Statistical Package for the Social Sciences (SPSS) software. The descriptive data were expressed as mean with standard deviation, percentage and counts. The paired Student’s t ‑test was used to evaluate the difference between the two groups. A P -value less than 0.05 was considered significant.

25. RESULTS

26. RESULT - SUMMARY The mean winter serum cortisol level at 06:00 AM was significantly higher than at 09:00 AM, and the mean summer cortisol level at 06:00 AM was significantly higher than at 09:00 AM. The overall mean cortisol level, regardless of season, at 06:00 AM (13.3 μg /dL) was significantly higher than at 09:00 AM (8.0 μg /dL) with a P- value of <0.001. However, there was no statistically significant difference in the mean serum cortisol levels between winter and summer at both 06:00 AM and 09:00 AM. The mean fall in overall serum cortisol from 06:00 AM to 09:00 AM was 39.8% (5.3 μg /dL).

27. DISCUSSION Serum cortisol at 09:00 AM was significantly less when compared to 06:00 AM across both the summer and winter seasons, indicating that an earlier sunrise in Guwahati led to an earlier acrophase of cortisol secretion and started falling after that. Also with each hour delay in sunrise, the acrophase of cortisol would be delayed. This finding aligns with a Hadlow N et al study which reported that for each hour delay in a sunrise the cortisol increased by 6.9%. Hadlow N, Brown S, Wardrop R, Conradie J, Henley D. Where in the world? Latitude, longitude and season contribute to the complex co‑ordinates determining cortisol levels. Clin Endocrinol ( Oxf ) 2018;89:299‑307 The serum cortisol rose 50% after exposure to bright light from dim light in the early morning, whereas cortisol did not rise in the afternoon for the same bright light. This suggests that the HPA axis response to light is dependent on the time of the day.

28. In this study 20% of subjects had a 09:00 AM cortisol sample value less than 5 μg /dL, which was falsely suggestive of adrenal insufficiency , whereas none of the samples at 06:00 AM had cortisol sample value less than 5 μg /dL . R esult of this study suggest that IST 06:00 AM is more preferred time for basal cortisol sampling in Guwahati, Assam , rather than between 08:00 AM to 09:00 AM to assess adrenal function. But in this study, there is no significant seasonal variation in serum cortisol levels between winter and summer. A previous Hadlow NC et al study reported that cortisol was lower in spring or summer and higher in winter or autumn . Hadlow NC, Brown S, Wardrop R, Henley D. The effects of season, daylight saving and time of sunrise on serum cortisol in a large population. Chronobiol Int 2014;31:243‑51 . M odern lifestyles and artificial lighting adopted in the present day may attenuate the influence of seasonal variations on cortisol secretion.

29. LIMITATIONS L ess sample size, which impacted the generalizability of the findings. This study assessed the effect of sunrise on cortisol levels at different timings in a north‑eastern part of India. A comparable group from other parts of India will allow for a more comprehensive analysis and comparison of cortisol levels between different regions with the effect of sunrise.

30. TAKE HOME MESSAGE It is essential to consider the influence of earlier sunrise on the circadian rhythm of cortisol secretion and sampling protocols. By recognizing the temporal discrepancies and adjusting the sampling time accordingly, we can improve the accuracy of cortisol assessments, avoid unnecessary testing ( i.e ACTH stimulation test) and ensure appropriate diagnosis and management of adrenal function . Also , by Measuring plasma ACTH simultaneously with serum cortisol could provide a more comprehensive understanding of interpreting the true value of cortisol.

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