Biology · Coordination and Control

Melatonin is a hormone secreted by the pineal gland that helps regulate our diurnal (daily) rhythms, including sleep-wake cycles.

Follicle-stimulating hormone (FSH) is not involved in regulating diurnal rhythms. It plays a role in reproductive processes, such as the development of eggs in females and sperm in males.

Melanocyte-stimulating hormone (MSH) is involved in skin pigmentation and has no direct role in regulating diurnal rhythms.

Melatonin contributes to the functioning of our biological clock. It is usually released in the dark and regulates our sleep and wake cycles.

Prolactin is a hormone that stimulates milk production in mammals but is not directly involved in regulating diurnal rhythms.