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Melatonin rhythm in human milk
H Illnerová1, M Buresová, J Presl
1Institute of Physiology, Academy of Sciences, Prague, Czech Republic.
The Journal of Clinical Endocrinology and Metabolism
|September 1, 1993
Summary
Human milk contains the pineal hormone melatonin, which follows a daily rhythm. This finding suggests that melatonin in breast milk may signal the time of day to infants.
Area of Science:
- Endocrinology
- Neonatal Nutrition
- Chronobiology
Background:
- The pineal hormone melatonin is known to exhibit circadian rhythms in body fluids.
- Data regarding melatonin levels in human milk were previously unavailable.
Purpose of the Study:
- To determine if melatonin is detectable in human milk.
- To investigate whether melatonin in human milk exhibits a daily rhythm.
Main Methods:
- Blood and milk samples were collected from 10 mothers postpartum (3-4 days after delivery) during daytime (1400-1700 h) and nighttime (0200-0400 h).
- Six mothers collected milk samples every hour over a 24-hour period within 3 months postpartum.
- Melatonin concentrations were measured using established assays.
Main Results:
- Melatonin was undetectable in both serum and milk during the day.
- Nighttime melatonin concentrations were 280 ± 34 pmol/L in serum and 99 ± 26 pmol/L in milk.
- All subjects showed a distinct daily rhythm of melatonin in milk, with high levels at night and undetectable levels during the day.
Conclusions:
- Melatonin is present in human milk and exhibits a pronounced daily rhythm.
- These findings suggest that melatonin in human milk may convey time-of-day information to breastfed infants.
- This hormonal signal could play a role in infant circadian system development.