Circulating Cardiac Troponin T Exhibits a Diurnal Rhythm
What are the within-day, diurnal, and between-week biological variations of cardiac troponin T (cTnT) in subjects with increased odds to require hospital examination for chest pain?
Two studies were conducted to assess biological cTnT variation, and investigate the presence of a diurnal rhythm of cTnT. Study 1 comprised 23 male subjects with type 2 diabetes, without acute cardiovascular disease. Serial venous blood samples were drawn over an 11-hour period (08:30-19:30 hours). In study 2, the presence of a diurnal cTnT rhythm was investigated by hourly sampling of seven subjects from study 1 over 25 hours.
In study 1, the investigators observed a gradual decrease in cTnT concentrations during the day (24 ± 2%). This decrease was present in all participants and most prominent in subjects with the highest baseline cTnT values (Pearson’s R 0.93). Diurnal variation of cTnT, as assessed in study 2, was characterized by peak concentrations during morning hours (08:30 hours,17.1 ± 2.9 ng/L), gradually decreasing values during daytime (20:30 hours,11.9 ± 1.6 ng/L), and rising concentrations during nighttime (08:30 hours next day,16.9 ± 2.8 ng/L).
The authors concluded that a diurnal cTnT rhythm substantiates the recommendation that all dynamic changes of cTnT should be interpreted in relation to the clinical presentation.
The current study suggests that circulating cTnT exhibits a diurnal rhythm, characterized by peak concentrations during morning hours, gradually decreasing concentrations throughout the daytime, and rising concentrations during nighttime. This diurnal oscillation is a general phenomenon, but is most prominent in subjects with the highest cTnT values. The presence of a diurnal rhythm has implications for epidemiological studies, and underscores the importance of interpreting all dynamic changes of cTnT in the context of the clinical presentation.
Keywords: Chest Pain, Diabetes Mellitus, Type 2, Epidemiologic Studies, Circadian Rhythm, Troponin T
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