Hershey, Pa. --- New research from Penn State's College of Medicine shows that the menstrual function develops rapidly after the first period (menarche), accompanied by a burst of hormones and no increase in the percent of body fat.
This new information is counter to previous studies, indicating that maturation of the reproductive process is gradual lasting from 4 to 6 years and was accompanied by an increase in percent body fat.
"These results suggests that not only has the age of menarche progressively dropped, but there may also be an acceleration in the rate of development during the years surrounding menarche," explains Richard S. Legro, M.D., associate professor of obstetrics and gynecology. "It also holds important implications for adolescent pregnancy and initiation of contraception for women immediately after menarche."
Legro and his colleagues' paper titled, "Rapid Maturation of the Reproductive Axis During Perimenarche Independent of Body Composition," is published in the March issue of The Journal of Clinical Endocrinology and Metabolism.
Legro and his colleagues studied 112 premenarchal (prior to the beginning of menstrual function) young women. The four-year study obtained detailed reproductive and dietary histories of the subjects, measured body composition, and also quantified reproductive hormones with urine samples.
The study found that the percentage of body fat did not change appreciably ranging from 21 to 24 percent and was unrelated to menarche (the beginning of the menstrual function). Legro and his colleagues also report that sex steroid and gonadotropin levels increased suddenly in the year approaching menarche. In the first year after menarche, 65 percent of these adolescent women had established a pattern of 10 or more menstrual episodes per year, and within 3 years postmenarche this figure exceeded 90 percent.
"The strength of our study is the regular follow-up of a large group of young women recruited before menarche, with good study retention and intensive evaluation. During the study 79 percent of the participants remained in the study," states the Penn State College of Medicine researcher.
"This is a retention rate far exceeding those in previous studies of this type." Legro added, "The transition in a female's life from adolescence to menstruating woman is still not fully understood, yet it is as important as the transition from menstruating woman to menopausal woman."