Which human endocrine gland is responsible for secreting the hormone melatonin, which regulates circadian rhythms and sleep-wake cycles?

💡 Solution & Explanation

The pineal gland is a small endocrine gland located near the center of the brain that synthesizes and secretes melatonin in response to darkness, modulating biological sleep rhythms. The thyroid gland produces hormones regulating basal metabolic rates, while adrenal glands secrete cortisol and adrenaline responding to stress. The thymus gland plays an essential role in T-lymphocyte maturation during immune development. Melatonin synthesis is stimulated by darkness and inhibited by light exposure.