Positive Relationship Between the Nocturnal Concentrations of Melatonin and Prolactin, and a Stimulation of Prolactin After Melatonin Administration in Young Men

Publisher Website
Google Scholar
Abstract
The relationship between the concentrations of melatonin and prolactin over the 24-h cycle has been investigated in a group of young men at three times in the year. Melatonin and prolactin showed a significant positive correlation (P < 0.001) for all times during the 24-h period but with a greater contribution from concentrations during the nocturnal period, when both hormones were elevated. The positive correlation for nocturnal concentrations was evident in February and March (P < 0.01) but was of greatest significance in June (P < 0.001). In blood samples taken at 15-min intervals during the morning (0800-1200) and evening (2000-2400), melatonin and prolactin concentrations were not significantly correlated. Melatonin concentrations increased before prolactin during the evening and decreased before prolactin in the morning. Oral administration of 6 mg melatonin significantly stimulated prolactin release above concentrations measured after placebo administration, in both the morning (P < 0.05) and evening (P < 0.01) time periods; the prolactin response being greater in the evening. These results provide evidence for melatonin controlling the nocturnal increase of prolactin via its ability to stimulate prolactin release.