Which hormone helps to regulate the circadian rhythms of the body?

The hormone that plays a crucial role in regulating the circadian rhythms of the body is melatonin. Melatonin is produced by the pineal gland in response to darkness, signaling the body that it is time to sleep and helping to maintain the sleep-wake cycle. This hormone’s secretion is influenced by light exposure, increasing in the evening and decreasing during daylight. By helping to establish and maintain these natural rhythms, melatonin is integral in coordinating bodily functions with the day-night cycle.

While cortisol, insulin, and thyroxine each have important biological functions, they do not primarily regulate circadian rhythms. Cortisol is a hormone that helps manage stress and is often highest in the early morning, aligning with wakefulness, but it does not control the circadian cycle. Insulin primarily regulates glucose metabolism, while thyroxine influences metabolism and growth but is not directly involved in regulating the sleep-wake cycle. Therefore, melatonin stands out as the key hormone for this specific function.