title: Morning urinary assessment of nocturnal melatonin secretion in older women.
abstract: We evaluated the feasibility of using morning urine samples in epidemiological studies aimed at clarifying the relationship between nocturnal melatonin levels and breast cancer risk. Initially, a laboratory-based study of 29 women (40- 70 yr old) was performed to examine the correlation between plasma melatonin levels in hourly nocturnal blood samples and both melatonin and its major enzymatic metabolite, 6-hydroxymelatonin-sulfate (6-OHMS) in morning urine samples. In a companion field study, morning urine samples were collected from 203 healthy women to assess similarities and differences in laboratory versus field measures. Taken together, our results indicate: 1) levels of melatonin and of creatinine-corrected 6-OHMS in the first morning void urine are strongly correlated with total nocturnal plasma melatonin output (P < 0.001) and also with peak nocturnal melatonin values (P < 0.001); 2) similar ranges for 6-OHMS were found in the laboratory and the field; and 3) neither menopausal status nor hormonal replacement therapy altered 6-OHMS values in morning void urine. The inclusion of morning urine samples in epidemiological studies of cancer could allow cost-effective, widespread testing of the role played by melatonin in human health and disease.
authors.affiliation: Midwest Research Institute, Kansas City, Missouri 64110, USA. mcook@mriresearch.org
authors.forename: M R
authors.initials: MR
authors.lastname: Cook
authors.forename: C
authors.initials: C
authors.lastname: Graham
authors.forename: R
authors.initials: R
authors.lastname: Kavet
authors.forename: R G
authors.initials: RG
authors.lastname: Stevens
authors.forename: S
authors.initials: S
authors.lastname: Davis
authors.forename: L
authors.initials: L
authors.lastname: Kheifets
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000097:blood / Q000453:epidemiology / Q000652:urine; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008550:Melatonin / Q000031:analogs & derivatives / Q000097:blood* / Q000652:urine*; D008875:Middle Aged; D010870:Pineal Gland / Q000378:metabolism*; D011863:Radioimmunoassay; D012307:Risk Factors
chemical_list: C054513:6-sulfatoxymelatonin; D008550:Melatonin