Overview
This lecture explains melatonin, a hormone that regulates the sleep-wake cycle, its functions in the body, related health conditions, and considerations for using melatonin supplements.
What Is Melatonin?
- Melatonin is a hormone made by the pineal gland in the brain.
- It regulates the body's natural sleep-wake cycle (circadian rhythm).
- Naturally produced melatonin is called endogenous; lab-made melatonin supplements are exogenous.
Melatonin Function and Regulation
- Melatonin helps the body prepare for sleep but does not directly induce sleep.
- Its production increases with darkness and decreases with exposure to light.
- Long nights (e.g., winter) lead to increased melatonin secretion.
How Melatonin Works
- Melatonin signals the hypothalamus to slow body functions like temperature, blood pressure, and mood to aid sleep.
- In the eyes, it reduces retina responsiveness to light, helping you feel less alert before sleep.
- Morning light lowers melatonin, signaling wakefulness.
Benefits and Roles Beyond Sleep
- Melatonin is essential for overall sleep, which affects hair, organs, mental health, and skin.
- It helps maintain regular menstrual cycles.
- It may protect brain health and slow certain types of age-related brain cell breakdown.
- Some evidence suggests melatonin could have anti-aging properties.
Melatonin Levels and Changes
- Females generally have higher melatonin levels than males.
- Babies receive melatonin from the mother before birth and start producing it at 3-4 months old.
- Melatonin peaks before puberty, decreases after puberty, and declines further after age 40.
Conditions Related to Melatonin
- Hypomelatoninemia: Low melatonin levels, leading to circadian rhythm sleep disorders such as trouble falling asleep, waking, or poor sleep quality.
- Hypermelatoninemia: High melatonin levels, commonly caused by overuse of supplements, and linked to eating disorders, hormone imbalances, and rare conditions.
Using Melatonin Supplements
- Melatonin supplements are not FDA-approved to treat conditions or guarantee sleep improvement.
- The FDA does not regulate supplements; consult a healthcare provider before starting melatonin.
- Supplements may interact with other medications or have side effects.
Key Terms & Definitions
- Melatonin — Hormone regulating the sleep-wake cycle, mainly produced in the pineal gland.
- Pineal gland — Gland in the brain responsible for melatonin production.
- Circadian rhythm — Biological process controlling sleep-wake cycles in roughly 24-hour periods.
- Endogenous — Produced within the body.
- Exogenous — Produced outside the body, e.g., synthetic supplements.
- Hypothalamus — Brain region controlling various bodily functions, influenced by melatonin.
- Hypomelatoninemia — Lower-than-normal melatonin levels.
- Hypermelatoninemia — Higher-than-normal melatonin levels.
Action Items / Next Steps
- Consult your healthcare provider if experiencing sleep problems or before taking melatonin supplements.