Anita Mantri, B.S.
Since the introduction of “the pill,” its use as a form of birth control and contraception has steadily increased in women of child-bearing age as seen in reports from the CDC. When the pill first came out in the 1970s, its use was very limited out of caution about the unknown effects of adding extra hormones to the body. Usually, the hormones estrogen and progesterone have distinct cycling patterns that prepare a woman’s body for pregnancy and lead to her period each month. When we add to this hormone pool in the blood, we can actually trick the body into thinking that it’s not that time of the month yet. Therefore, we can prevent pregnancy and additionally control exactly when periods occur. Older research has helped to define the changes in menstrual cycling as well as tissue changes in female reproductive organs. However, the use of birth control pills has become so popular recently that many women use them to reduce the total number of periods they have each year. The question arises as to whether or not their use has additional effects on other tissues in the body, such as bone. Generally, we know that exercise helps to maintain strong and healthy bones. However, in 2000, two papers published by David Burr and Connie Weaver showed that when healthy women were taking birth control pills and exercising at the same time over the course of two years, bone density in their lower spines was decreased compared to women not taking anything at all performing same amount of exercise. In addition, these women were shown to have decreased rates of normal bone turnover, which may prevent exercise’s ability to increase bone density and strength at the femoral neck (the bone found at the hip joint).
In a sense, these results seem counterintuitive. What exactly is causing this blunted effect in bone density and hip strength? Because of the limitations of human research, it would be incredibly useful to have an appropriate animal model to discover the underlying causes for this effect. The trouble is that no one knows what dose of estrogen would be needed to prevent female animals from having a period. Therefore, before we can really get into what effects birth control has on the body, we have to develop a good research model to mimic birth control pill usage. Based on data from animal research, we can then investigate what effects contraceptives have on the rest of the body, not just female reproductive organs.
As we come upon 50 years of women being on the pill, contraceptive development, and the feminist movement, women today deserve to know out how the added hormones of contraceptive medications truly affect them. Through animal research, we can investigate what effects they have on the whole woman rather than just focusing on her periods and fertility.
- Exercise and oral contraceptive use suppress the normal age-related increase in bone mass and strength of the femoral neck in women 18-31 years of age. D.B. Burr, T.Yoshikawa, D. Teegarden, R. Lyle, G. McCabe, L.D. McCabe and C.M. Weaver. Bone 855-863. 2000.