Which of the following hormone is secreted by brain that helps to regulate sleep-wake cycles?

Melatonin

The correct answer is Option (2)- Melatonin

The hormone secreted by the brain that helps regulate sleep-wake cycles is Melatonin.

Explanation:

Melatonin is produced by the pineal gland, a small endocrine gland located in the brain. The pineal gland responds to changes in light and darkness, with melatonin production increasing in response to darkness and decreasing in response to light. This hormone plays a crucial role in the circadian rhythm, helping to regulate the sleep-wake cycle.

Melatonin levels typically rise in the evening as it gets dark, promoting a state of drowsiness and preparing the body for sleep. In the morning, when it becomes light, melatonin levels decrease, signaling wakefulness.

The other hormones listed—Insulin, Oxytocin, and Aldosterone—serve different functions in the body, such as regulating blood sugar, promoting social bonding and childbirth, and maintaining electrolyte balance, respectively, but they are not primarily involved in the regulation of sleep-wake cycles.