Measuring serum melatonin in postmenopausal women: Implications for epidemiologic studies and breast cancer studies

• Published in: PloS one Vol. 13; no. 4; p. e0195666
• Main Authors: Chu, Lisa W, John, Esther M, Yang, Baiyu, Kurian, Allison W, Zia, Yasaman, Yu, Kai, Ingles, Sue A, Stanczyk, Frank Z, Hsing, Ann W
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11-04-2018; Public Library of Science (PLoS)
• Subjects: Aged; Aged, 80 and over; Analysis; Bioindicators; Biological markers; Biology and Life Sciences; Biomarkers; Blood Chemical Analysis - methods; Breast cancer; Breast Neoplasms - blood; Cancer; Circadian rhythm; Circadian rhythms; Coefficient of variation; Complications and side effects; Development and progression; Disease prevention; Epidemiologic Studies; Epidemiology; Etiology; Female; Gynecology; Health aspects; Health risk assessment; Humans; Light; Magnetic fields; Measurement; Medical research; Medicine and Health Sciences; Melatonin; Melatonin - blood; Middle Aged; Morning; Obstetrics; Post-menopause; Postmenopausal women; Postmenopause - blood; Preventive medicine; Radioimmunoassay; Reproducibility; Shift work; Sleep; Studies; Time Factors; Urine; Womens health; Los Angeles California; San Francisco Bay; California; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0195666

Circulating melatonin is a good candidate biomarker for studies of circadian rhythms and circadian disruption. However, epidemiologic studies on circulating melatonin are limited because melatonin is secreted at night, yet most epidemiologic studies collect blood during the day when melatonin levels are very low, and assays are lacking that are ultrasensitive to detect low levels of melatonin reliably.
To assess the performance of a refined radioimmunoassay in measuring morning melatonin among women.
We used morning serum samples from 47 postmenopausal women ages 48-80 years without a history of breast cancer who participated in the San Francisco Bay Area Breast Cancer Study, including 19 women who had duplicate measurements. The coefficient of variation (CV) and intraclass coefficient (ICC) were estimated using the random effect model.
Reproducibility for the assay was satisfactory, with a CV of 11.2% and an ICC of 98.9%; correlation between the replicate samples was also high (R = 0.96). In the 47 women, serum melatonin levels ranged from 0.6 to 62.6 pg/ml, with a median of 7.0 pg/ml.
Our results suggest that it is possible to reliably measure melatonin in postmenopausal women in morning serum samples in large epidemiologic studies to evaluate the role of melatonin in cancer etiology or prognosis.