Cortisol Circadian Peak — FRCA Primary MCQ

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HardPhysiology - Endocrine & MetabolicCortisol Circadian PeakFRCA Primary

In a healthy person with a normal sleep–wake cycle, when is plasma cortisol concentration usually highest?

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Correct answer: E — Around 08:00 near the usual waking period

The best answer is “Around 08:00 near the usual waking period”. Cortisol secretion is pulsatile and has a circadian peak around the early morning waking period, commonly near 08:00, with a nadir near midnight. Acute illness, major surgery and exogenous glucocorticoids can alter this pattern, but they do not change the normal circadian reference point tested here.

Reference: Royal College of Anaesthetists, Primary FRCA Syllabus 2021: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf