Specific quantitation of urinary 6-hydroxymelatonin sulphate by gas chromatography mass spectrometry

6-Hydroxymelatonin sulphate, a unique urinary metabolite of melatonin, has been measured in human subjects for the first time using a chromatography mass spectrometry and an isotope labelled internal standard. Urinary levels in both males and females were similar and ranged from 25-125 nmol 24 h-1. A significant nocturnal elevations of 6-hydroxymelatonin sulphate was also established in a male subject.