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The circadian thyrotropin rhythm is delayed in regular night workers
L Weibel1, G Brandenberger, B Goichot
1Laboratoire de Physiologie et de Psychologie Environnementales, CNRS, Strasbourg, France.
Neuroscience Letters
|March 3, 1995
Summary
The circadian thyrotropin (thyroid-stimulating hormone, TSH) rhythm adapts to night work, aligning with body temperature shifts during sleep onset. This suggests TSH rhythm orientation can indicate the body's internal clock timing.
Area of Science:
- Chronobiology
- Endocrinology
- Sleep Medicine
Background:
- Circadian rhythms govern physiological processes, including hormone secretion.
- Thyrotropin (TSH) exhibits a distinct circadian rhythm, typically peaking during sleep.
- Adaptation of these rhythms to altered sleep schedules, like night work, is not fully understood.
Purpose of the Study:
- To investigate if the circadian rhythm of thyrotropin (TSH) adjusts to a night-active schedule.
- To examine the phase relationship between TSH and body temperature rhythms in night workers versus day-active individuals.
Main Methods:
- Collected plasma TSH and body temperature every 10 minutes for 28 hours.
- Studied 8 regular night workers and 8 day-active control subjects.
- Analyzed acrophase (peak time) and nadir (trough time) of TSH and body temperature rhythms.
Main Results:
- Night workers showed a significant shift in TSH acrophase, occurring around sleep onset, similar to day-active subjects.
- Body temperature nadir also shifted to occur during the sleep period in night workers.
- TSH and body temperature rhythms maintained a consistent phase relationship in both groups, despite schedule differences.
Conclusions:
- The circadian TSH rhythm, along with body temperature, adapts to regular night work.
- TSH acrophase demonstrates a fixed phase relationship with body temperature, indicating rhythm adjustment.
- TSH rhythm orientation may serve as a reliable indicator for assessing the endogenous clock's alignment.