Question 1

Q: Which hormone(s) exhibit(s) increased production during the day and decreased production at night?

All of the above. **Explanation:** The circadian rhythm is an internal biological clock regulated by the **Suprachiasmatic Nucleus (SCN)** of the hypothalamus. It coordinates the secretion of various hormones to align with the body’s metabolic needs during the activity (day) and rest (night) cycles. **1. ACTH and Cortisol (Options A & B):** The Hypothalamic-Pituitary-Adrenal (HPA) axis follows a distinct diurnal pattern. ACTH and Cortisol levels begin to rise in the early morning hours (around 3–4 AM), peaking just before or shortly after waking (the **Cortisol Awakening Response**). This prepares the body for daytime stress and activity by increasing blood glucose through gluconeogenesis. Conversely, levels reach their nadir (lowest point) around midnight. **2. Insulin (Option C):** Insulin secretion also exhibits a circadian rhythm, peaking during the day and decreasing at night. This is partly due to increased daytime food intake (postprandial spikes) and an inherent circadian regulation that enhances beta-cell sensitivity during the light phase to optimize glucose disposal. **Conclusion:** Since ACTH, Cortisol, and Insulin all show higher secretory activity during the day compared to the night, **Option D** is the correct answer. **High-Yield NEET-PG Pearls:** * **Melatonin:** The "hormone of darkness"; unlike the options above, it peaks at night (2–4 AM) and is inhibited by light. * **Growth Hormone (GH):** Secretion is pulsatile but shows a major peak during **Stage 3 (N3) Non-REM sleep**. * **Prolactin:** Levels also rise during sleep and peak in the early morning. * **Clinical Correlation:** Night shift workers or those with irregular sleep patterns often face "circadian misalignment," increasing the risk of metabolic syndrome and Type 2 Diabetes due to disrupted insulin and cortisol rhythms.

Question

Which hormone(s) exhibit(s) increased production during the day and decreased production at night?

Accepted Answer

All of the above

Answer

Adrenocorticotropic hormone (ACTH)

Answer

Cortisol

Answer

Insulin

Chronobiology and Circadian Rhythms — MCQs

Chronobiology and Circadian Rhythms — MCQs

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