Morning Urinary Assessment of Nocturnal Melatonin Secretion in Older Women

J Pineal Res. 2000 Jan;28(1):41-7. doi: 10.1034/j.1600-079x.2000.280106.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Breast Neoplasms / blood
  • Breast Neoplasms / epidemiology
  • Breast Neoplasms / urine
  • Circadian Rhythm*
  • Female
  • Humans
  • Melatonin / analogs & derivatives
  • Melatonin / blood*
  • Melatonin / urine*
  • Middle Aged
  • Pineal Gland / metabolism*
  • Radioimmunoassay
  • Risk Factors


  • 6-sulfatoxymelatonin
  • Melatonin