Researchers Investigate Years Before Menopause

February 15, 1998

University Park, Pa. -- Baby boomers in a long-term study of women's reproductive cycles are helping Penn State researchers map the uncharted years of perimenopause, the several years leading up to menopause.

The researchers are investigating how women's health and reproductive histories affect the patterns of change during permimenopause and after.

"Anything that takes us a step further in identifying the changes leading up to menopause will be very helpful," says Dr. James W. Wood, professor of anthropology and senior research scientist in Penn State's Population Research Institute.

The researchers are collecting first morning urine samples from approximately 150 women ages 35 to 60 for six months of each year during the five-year project which began this year. The samples will be analyzed for the metabolic remains of four hormones linked with the monthly female reproductive cycle -- estrogen, progesterone, luteinizing hormone and follicle stimulating hormone.

While collecting 28,000 samples a year for five years and analyzing them is a daunting task, understanding variations among women and being able to model changes could benefit women in such ways as guiding women and their physicians in making choices about hormone replacement therapy.

"This research would not be possible without the Tremin Trust," Wood told attendees today (Feb. 15) at the annual meeting of the American Association for the Advancement of Science in Philadelphia. "The dedication of these women is amazing."

The Tremin Trust, begun at the University of Minnesota by Alan Treloar in 1934, enrolled university women in a long term reproductive study. The first cohort of women was recruited in the 1930s and the second in the 1960s and 1970s. Both cohorts have kept continual calendars indicating the starting and ending dates of their monthly periods. Annual health surveys are done each year and include information on births, abortions, miscarriages, surgery, marriage, divorce and stressful events as well as general health and birth control information. In 1984, the trust moved to the University of Utah under the oversight of Ann Voda in the School of Nursing.

"Only the Trust data can supply this kind of long-term data on women's reproductive health," says Wood "There is no other long-term study of this type."

More women today are living into their 90s, spending the same or more years post menopausal than fertile. The health implications of the hormone patterns of perimenopause for women at these post menopausal ages has not been explored.

Women are born with all the ovarian follicles -- egg precursors -- they will ever have. Each month a number of egg precursors begin to grow, but normally most die off leaving one egg per cycle to ovulate. As women age, they have fewer and fewer follicles left until no follicles remain.

The standard medical definition of menopause is 12 continuous months without menstrual bleeding. Because the follicles control the cycle of hormones that lead to preparation of the uterus for egg implantation and eventually to menstruation when no egg is fertilized, menopause occurs when all the follicles are used up. It is typical for women to experience variable cycles, including very long cycles when approaching menopause. The patterns of perimenopause vary among women in ways that are poorly understood.

Little is known about how life histories affect the patterns leading to menopause. Smoking is thought to lower the age of menopause, while the effects of hormones from birth control pills and replacement therapy are unknown.

The researchers include Wood; Kathleen O'Connor, post doctoral trainee and Dr. Darryl Holman, postdoctoral fellow in Penn State's Population Research Institute, and Dr. Phyllis Mansfield, professor of women's studies and health education. The study is funded by the National Institutes of Health and the Penn State researchers are working with researchers from Georgetown University and Princeton University.


EDITOR: Dr. Wood may be reached at (814) 865-1936 or

Penn State

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