Estimation of frequently sampled nocturnal melatonin production in humans by deconvolution analysis: Evidence for episodic or ultradian secretion

In order to investigate nocturnal melatonin production and clearance rates, we applied deconvolution analysis to plasma melatonin concentration time series obtained every 20 min for 12 hr from 20:00 h to 08:00 h in two groups of healthy subjects at rest (group 1, 12 male subjects, 22-26 yr; group 2, ten female subjects, 31-42 yr). The estimated melatonin production rate from group 1 (0.55 ± 0.21 μg/kg/night) was significantly higher than that of group 2 (0.26 ± 0.19 μg/kg/night), as well as the mass of melatonin released per burst (275 ± 110 vs. 145 ± 130 pg/mL for groups 1 and 2, respectively), the amplitude of secretory bursts (7.8 ± 3.2 vs. 4.7 ± 3.5 pg/mL/min), and the pulsatile melatonin production rate (2.76 ± 1.14 vs. 1.27 ± 0.97 ng/mL/night). These differences could reflect alterations related to age and/or gender. No differences were observed between the two groups in the secretory burst half-duration and frequency and the interburst interval. Melatonin production rates, as estimated by deconvolution analysis, are in agreement with other independent estimates, especially the isotopic method, and disclose an ultradian rhythmicity.