Circadian secretion patterns of melatonin after major surgery

Area of Science:

• Physiology
• Endocrinology
• Surgical Science

Background:

• Circadian rhythms, including core body temperature and melatonin secretion, are regulated by a biological clock.
• Major surgery, particularly esophagectomy with thoracotomy, can impact physiological rhythms.
• Melatonin is a key marker for circadian rhythmicity, influenced by light and biological clock function.

Purpose of the Study:

• To investigate the impact of major surgery (esophagectomy with thoracotomy) on the circadian rhythm of melatonin secretion.
• To determine if the stress of invasive surgery significantly disturbs melatonin secretion patterns postoperatively.

Main Methods:

• Plasma melatonin concentrations were measured sequentially in seven patients undergoing esophagectomy with thoracotomy.
• Blood samples were collected at multiple time points on the first postoperative day, with extended monitoring for one patient up to six days.
• Radioimmunoassay (RIA) was used to quantify melatonin levels.

Main Results:

• Five out of seven patients demonstrated circadian secretion patterns of melatonin on the first postoperative day.
• Four patients had elevated melatonin concentrations (>30 pg/ml) at 24:00 hr on the first postoperative day.
• One patient exhibited a regular circadian secretion pattern for the entire six-day monitoring period.

Conclusions:

• The circadian secretion pattern of melatonin remained largely intact in most patients following major esophagectomy with thoracotomy.
• The biological clock's regulation of melatonin secretion appears resilient to the stress of major invasive surgery.
• Melatonin secretion can serve as a reliable indicator of circadian rhythmicity even after significant surgical procedures.