Distinct modes of melatonin secretion in normal men

Area of Science:

• Endocrinology
• Neuroscience
• Chronobiology

Background:

• Melatonin, a hormone primarily secreted by the pineal gland, exhibits a circadian rhythm.
• The pulsatile nature of melatonin secretion and the presence of superimposed short-term episodes have been subjects of recent investigation.
• Plasma melatonin levels are influenced by secretion, distribution, and degradation, necessitating methods to estimate secretory rates.

Purpose of the Study:

• To estimate melatonin secretory rates from peripheral levels using a deconvolution procedure.
• To analyze the pulsatile pattern of melatonin secretion in healthy adult men.
• To determine if episodic secretion is superimposed on tonic basal secretion.

Main Methods:

• Fourteen healthy male volunteers participated in overnight studies (2300-0700) in darkness.
• Plasma melatonin levels were measured every 10 minutes using radioimmunoassay.
• Pulse analysis was conducted using the ULTRA computer program to estimate secretory rates and patterns.

Main Results:

• Approximately 30% more secretory pulses were detected than previously reported.
• Episodic melatonin secretion was observed to be superimposed on tonic basal secretion.
• Significant interindividual variability was found in the number, amplitude, and timing of pulses, as well as the mean secretory rate.

Conclusions:

• Melatonin secretion in healthy adult men operates in two distinct modes: tonic and episodic.
• Episodic secretion is variably superimposed on tonic secretion, with proportions differing between individuals.
• Despite interindividual variability, replicate studies showed consistent secretory profiles within subjects.