title: Melatonin: marvel or marker?
abstract: Melatonin blanches the skin of frogs, whitens the fur of hamsters, and sometimes makes the gonads atrophy. It is remarkable that such a hormone would be put forward as a defense against ageing. We have been examining excretion of the urinary metabolite of melatonin, 6-sulphatoxymelatonin (6-SMT), in 150 postmenopausal women, in 72 volunteers over the age of 60 years who complained of insomnia or depression, and in 20 healthy younger adult controls, aged 18-40 years. The acrophase or fitted peak of 6-SMT excretion was computed as a marker of the timing of the circadian system. Total daily excretion of 6-SMT was not significantly related to total sleep time, wake-within-sleep or sleep complaints. Nevertheless, whereas the 20 controls displayed a normal range of 6-SMT acrophases from 01.32 to 05.44 h, 42% of the postmenopausal women and 48% of the symptomatic elders had acrophases outside this normal range. Those volunteers with more deviant acrophases displayed more disturbed sleep and more sleep complaints. These data suggest that melatonin is a useful marker of circadian rhythm phase disorders, but suggest a need for more caution in melatonin administration.
authors.affiliation: Department of Psychiatry and the Sam and Rose Stein Institute for Research on Aging, University of California, San Diego, La Jolla 92093-0667, USA. dkripke@ucsd.edu
authors.forename: D F
authors.initials: DF
authors.lastname: Kripke
authors.forename: J A
authors.initials: JA
authors.lastname: Elliot
authors.forename: S D
authors.initials: SD
authors.lastname: Youngstedt
authors.forename: J S
authors.initials: JS
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D003863:Depression / Q000503:physiopathology / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism / Q000502:physiology / Q000627:therapeutic use / Q000652:urine; D008875:Middle Aged; D017698:Postmenopause / Q000652:urine; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology / Q000652:urine
chemical_list: C054513:6-sulfatoxymelatonin; D008550:Melatonin