Effect of shift work on the night-time secretory patterns of melatonin, prolactin, cortisol and testosterone.
Level 4 - case-series / case-control
Small observational cross-sectional study with non-randomized control comparison
PubMed 2357985 · doi:10.1007/BF00379398
What was done
Researchers evaluated nocturnal hormone secretion in 4 male oil refinery operators aged 25-34 years on a fast-rotating shift schedule (every 3-4 days), drawn from a larger study of 12 shift workers. Blood was sampled every 2 hours during a night shift (0000 to 0800 hours) to measure secretory profiles of melatonin, prolactin, cortisol, and testosterone compared to controls.
What was found
Melatonin peak values were higher in shift workers, resulting in a four-times higher rhythm amplitude than in controls. Prolactin and testosterone concentrations were significantly decreased, with erratic peak and trough times. Serum cortisol showed decreased rhythm amplitude with higher concentrations at 0000 hours in shift workers. No apparent phase shift was observed for any hormone. The abstract provides relative changes but omits exact numerical concentrations and variance.
Why it matters
The findings indicate that fast-rotating shift work alters hormone levels and amplitudes during night shifts without necessarily causing circadian phase shifts.
Limits
The sample size of sampled shift workers was extremely small (n = 4), and details regarding the control group are absent. Sampling was restricted to an 8-hour nighttime window rather than a complete 24-hour cycle, and absolute numerical values and statistical test metrics were not reported in the abstract.
Cited by
- supports At around 10:30 to 11:30 PM, circulating levels of estrogen, testosterone, progesterone, adrenaline, and cortisol are low while melatonin levels are high.