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Diurnal variation of plasma cortisol levels in infancy
S Mantagos1, A Moustogiannis, A G Vagenakis
1Department of Pediatrics, University of Patras Medical School, Greece.
Insights
The cortisol circadian rhythm, a daily pattern of plasma cortisol levels, emerges between two and three months of age in infants. This study tracked cortisol levels in healthy infants to pinpoint when this biological rhythm develops.
Area of Science:
- Endocrinology
- Developmental Biology
- Pediatrics
Background:
- Adults and children exhibit diurnal variation in plasma cortisol levels, peaking in the morning and lowest at night.
- The precise age of onset for the cortisol circadian rhythm in infants remains unclear despite previous research.
Purpose of the Study:
- To investigate the developmental timeline of the cortisol circadian rhythm in human infants.
- To determine the age at which infants establish a discernible diurnal variation in plasma cortisol.
Main Methods:
- Plasma cortisol levels were measured in seventy healthy, full-term infants under six months old.
- Measurements were taken twice daily: once in the late morning (10:30 h) and once at night (22:30 h).
Main Results:
- No significant difference between daytime and nighttime cortisol levels was observed in infants during the first four weeks of life.
- A statistically significant difference (p < 0.05) between daytime and nighttime cortisol levels emerged between two and three months of age, persisting through six months.
Conclusions:
- The cortisol circadian rhythm begins to develop between the second and third months of infancy.
- This finding establishes a critical window for the maturation of the hypothalamic-pituitary-adrenal axis regulation in early life.
Abstract:
Normal children and adults show diurnal variation of plasma cortisol levels reaching peak values around 08.00 h and lower values around 24.00 h. Despite numerous studies on diurnal variation of plasma cortisol levels in children, the age of appearance of a circadian rhythm has not been definitely established. The purpose of this study was to investigate the development of cortisol circadian rhythm in infancy. In seventy healthy, full-term infants, less than six months old, plasma cortisol was measured at 10.30 h and 22.30 h. The mean +/- SEM values of daytime plasma cortisol at one to four weeks of life were 159 +/- 41, 116 +/- 43, 240 +/- 54 and 456 +/- 95 nmol/l and the night-time values were 129 +/- 40, 99 +/- 44, 131 +/- 78 and 430 +/- 105 nmol/l, respectively. No statistically significant differences were found between daytime and night-time cortisol values during the first four weeks of life. In contrast, the daytime values of plasma cortisol were 295 +/- 62 at the age of 2-3 months, 211 +/- 43 at 4-5 months and 291 +/- 31 nmol/l at 6 months of life, and night-time values were 166 +/- 52, 119 +/- 35 and 109 +/- 21 nmol/l, respectively, which were statistically significant (p < 0.05). These data clearly indicate that cortisol circadian rhythm starts between the second and third month of life.