Optometry Admission Test (OAT) Practice

What is the role of melatonin in the body?

1. Stimulates growth of hair

2. Regulates sleep-wake cycles

3. Maintains circadian rhythms

4. Promotes energy metabolism

The correct answer is: Maintains circadian rhythms

Melatonin plays a crucial role in maintaining circadian rhythms, which are the natural, internal processes that regulate the sleep-wake cycle and other physiological activities over a 24-hour period. Produced primarily by the pineal gland in response to darkness, melatonin helps signal to the body that it is time to sleep. This hormone regulates the timing of sleep and wakefulness, aligning these functions with the day-night cycle, thus ensuring that various biological processes remain synchronized with environmental cues. While melatonin does indeed have effects on sleep-wake cycles, its principal function is intricately tied to the maintenance of circadian rhythms. These rhythms influence not only sleep patterns but also other bodily functions such as hormone release, eating habits, and body temperature regulation, making them critical for overall health. The other options are not the primary functions of melatonin, as stimulating hair growth, promoting energy metabolism, and regulating sleep-wake cycles are not its main roles. Melatonin's most significant contribution revolves around ensuring the body's internal clock aligns with the external environment, emphasizing its importance in circadian rhythm regulation.