Susan Kidd1, Paula Midgley, Mary Nicol, John Smith, Neil McIntosh. 1. Department of Child Life and Health, University of Edinburgh and Neonatal Unit, Simpson Center for Reproductive Health, Royal Infirmary Edinburgh, Edinburgh, UK.
Abstract
BACKGROUND/AIMS: Knowledge of the presence or absence of cortisol (F) circadian rhythm in preterm infants is important for the interpretation of F measurements made in samples taken for both clinical and research purposes. Little is known about its emergence in very preterm infants. This study examines circadian rhythm in F secretion in hospitalized infants born before 30 weeks' gestation. DESIGN: Prospective longitudinal observational study. SUBJECTS: 11 infants admitted consecutively and born before 30 completed weeks of gestation. MEASUREMENTS: F was measured by highly specific radioimmunoassay on morning and evening saliva samples gathered at weekly intervals until discharged home. Circadian rhythm was defined as > or =40% reduction from morning to evening level. RESULTS: For all data, the median salivary F was 10.3 nmol/l (range <0.5-372.8). F levels were highest in the first 3 weeks of life. No infants displayed classical circadian rhythm for 4 weeks or more prior to being discharged from hospital. The other infants showed randomly distributed morning and evening F values with a trend in 4 infants towards periods of consistently higher evening than morning values. CONCLUSION: Adult-type F circadian rhythm is rarely evident in hospitalized preterm infants born before 30 weeks' gestation.
BACKGROUND/AIMS: Knowledge of the presence or absence of cortisol (F) circadian rhythm in preterm infants is important for the interpretation of F measurements made in samples taken for both clinical and research purposes. Little is known about its emergence in very preterm infants. This study examines circadian rhythm in F secretion in hospitalized infants born before 30 weeks' gestation. DESIGN: Prospective longitudinal observational study. SUBJECTS: 11 infants admitted consecutively and born before 30 completed weeks of gestation. MEASUREMENTS: F was measured by highly specific radioimmunoassay on morning and evening saliva samples gathered at weekly intervals until discharged home. Circadian rhythm was defined as > or =40% reduction from morning to evening level. RESULTS: For all data, the median salivary F was 10.3 nmol/l (range <0.5-372.8). F levels were highest in the first 3 weeks of life. No infants displayed classical circadian rhythm for 4 weeks or more prior to being discharged from hospital. The other infants showed randomly distributed morning and evening F values with a trend in 4 infants towards periods of consistently higher evening than morning values. CONCLUSION: Adult-type F circadian rhythm is rarely evident in hospitalized preterm infants born before 30 weeks' gestation.