Pineal Volume and Circadian Melatonin Profile in Healthy Volunteers: An Interdisciplinary Approach

Purpose: To correlate pineal parenchyma volume (PP) to circadian melatonin profiles and to determine the 24-hour melatonin per volume of pineal tissue (MLPV). Furthermore, we compared melatonin profiles of cystic and solid glands. Methods: In 15 healthy male subjects (20-27 years) the PP was determined using high-resolution magnetic resonance imaging (trueFISP, isotropic voxel: 0.8 mm(3)). Melatonin plasma concentrations (MC) were determined every 2 hours for 24 hours. Results: Mean PP was 125 2: 54 mm(3). PP correlated linearly to maximum MC and to 24-hour melatonin (r = 0.61 and r = 0.64, P < 0.05) but not to minimum MC. The 24-hour melatonin was 653 +/- 242.6 pg/mL, MLPV was 5.8 +/- 2.3 pg/mL*ml(-1). Nine pineal glands were solid and six were cystic. PP of solid glands showed higher linear correlations to maximum melatonin, to 24-hour melatonin, and to the slope of the melatonin increase of the curve (P < 0.05). Conclusion: PP correlates linearly to melatonin plasma concentrations in humans. MLPV displays similar interindividual differences as 24-hour melatonin. PP of solid glands show better correlation to melatonin profiles than cystic.