Menstrual cycle phases and exposure to environmental contaminants : Menstrual Cycle and Ovulation Study 2 (MOS2)

In 2006-2008, 610 premenopausal, spontaneously menstruating women in the Metro Vancouver region participated in a Canadian Institutes of Health Research (CIHR)-funded singlecycle in which they collected first morning urine specimens for estrogen and progesterone metabolites1. Following that study, after analyses, we retrieved the remaining urine specimens from the analyzing laboratory (University of Washington). We sorted data so that samples from all those women who were anovulatory by the two combined urinary steroid evaluation methods2,3, plus from those who were ovulatory with the highest and the lowest urinary hormone values were shipped to Health Canada (HC) via Dr. Warren Foster’s laboratory at McMaster University. Those data on flame retardant contaminants in women’s urine have been published4, but the cycle-phase specific data are still in analysis (personal communication, S Kalyan, 2019). In 2017, HC basic scientists launched applications to HC to fund a similar study to assess flame retardant excretory changes in the same population/locale 10 years later. This application was funded in 2018 at Health Canada with Dr. JC Prior as a collaborator. Extensive negotiations by CeMCOR and HC scientists ensued about funding the process of obtaining these follow-up specimens. CeMCOR managed to obtain a HC agreement to fund the minimal cost of recruiting, training and obtaining two menstrual phase-specific urine specimens from 250 Metro Vancouver women. Because of the lack of a progesterone threshold for ovulation, we will collect one follicular and one luteal/premenstrual urine sample per woman. However, this time we will better characterize the ovulatory cycle using a validated quantitative basal temperature method5,6 that can assess luteal phase length as well as the presence/absence of evidence for ovulation. In addition we will collect serial salivary progesterone and estradiol values measured by the state-of-the-art sensitive and specific tandem mass spectrometry (LC-MS/MS) methods7 to use as the gold standard for an ovulatory cycle. There is increasing evidence that many variables differ across women’s two main menstrual cycle phases: follicular and luteal7-10. These real and potential differences in metabolism may alter the susceptibility of women to environment exposures, and also could change their urinary elimination. Those are the root reasons for doing this study.