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 as 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 elevation of 6-hydroxymelatonin sulphate was also established in a male subject.