A pineal gland tumor can disrupt melatonin production and potentially affect which process?

• A. Growth hormone secretion.
• B. Sleep-wake circadian rhythm.
• C. Adrenal cortisol production.
• D. Insulin secretion.

Answer: (B)

Melatonin from the pineal gland helps coordinate the body's internal clock with the day-night cycle. When it gets dark, melatonin rises and promotes sleep, helping to set the timing and duration of sleep across the 24-hour day. If a pineal gland tumor disrupts melatonin production, the sleep-wake circadian rhythm can become misaligned, causing trouble falling asleep, waking during the night, or daytime fatigue due to being out of sync with the environment.

The other processes are governed by different systems: growth hormone secretion is controlled by the pituitary gland, adrenal cortisol production by the hypothalamic-pituitary-adrenal axis, and insulin secretion by the pancreas. While cortisol has its own circadian pattern, melatonin’s main influence is on when we sleep and our overall daily rhythm, not directly on those other secretions.