Estrogen and ACL
If estrogen directly inhibits collagen growth, then the more estrogens in a female's system the more athletic injuries she should incur at certain times of the month. During the menstrual cycle, the absolute levels of estrogen (Estradiol) and progesterone, and the ratio of these hormone concentrations, change over the mean cycle duration of 28 days. In the follicular phase (days 1 to 9), concentrations of both estrogen and progesterone are low. Ovulation (day 10 to 14) is preceded by a midcycle surge of estrogen. During this time, estrogen concentrations are at their highest. During the luteal phase (day 15 to end of cycle), progesterone levels rise significantly because of secretion by the corpus luteum, and relaxin levels increase halfway through this phase

Because women suffer four to eight times the number of ACL injuries for the same sports as men, Dr. Edward Wojtys and colleagues, at the University of Michigan in Ann Arbor, decided to look at when in the menstrual cycle these injuries occurred. (Wojtys, E. Association between the menstrual cycle and anterior cruciate ligament injuries in female athletes. American Journal of Sports Medicine. 1998; 26:614-619.) This study was designed to investigate the variation in ACL injury rates during the female monthly cycle. These injuries were noncontact ACL injuries, meaning they could not be injuries due to a female athlete being hit by another player. Twenty-eight women with ACL injuries were studied. Each woman was asked to provide a detailed history of her menstrual cycle, including frequency and regularity, date of last menstrual period, average length of cycle, premenstrual symptoms, and oral contraceptive or hormone replacement use. The study showed a significant association between the stage of the menstrual cycle and likelihood for an ACL injury In particular, there were more injuries during the ovulatory phase of women than expected. Female athletes were much more likely to injury their ACL during the ovulatory phase when estrogen levels are highest. Of interest is that 20 of the 28 believed that their individual athletic performance was hindered during this premenstrual time. This is another reason for women to seek out a Prolotherapy doctor who also uses natural medicine treatments and can relieve PMS using vitamins, herbs, and other nutritional remedies.

During a normal menstrual cycle, the estrogen concentration rises during day 10 and peaks on day 12. This is the peak time during which female athletes suffer ACL injuries. It was clear in this study that estrogen negatively affected the strength of ligament tissue, as injury rates were increased during this time. Other studies, in rabbits that have been ovariectomized (no estrogen), have documented that the estrogen given to them negatively affected the ligament strength. (Booth, F.W., Tipton, C.M.. Ligamentous strength measurements in pre-pubescent and pubescent rats. Growth. 1970; 34:177-185.; Slauterbeck, J. Effects of estrogen level on the tensile properties of the rabbit anterior cruciate ligament. Orthop. Trans. 1997; 21:747-748.)

The more estrogen given to these rabbits, the weaker their ligaments became.