Thank you for your question. The possibility that depot medroxyprogesterone, injections of medroxyprogesterone acetate150-mg, every three months (DMPA), may cause osteoporosis risk is now in the news because of a recent Federal Drug Agency warning from the USA.
First, all hormonal contraceptives act by suppressing the brain, pituitary and ovary. This means the ovaries make less estrogen and progesterone and don’t release eggs each month. In contrast to DMPA, the Pill supplies high doses of estrogen as well as progestin (synthetic progesterone). DMPA supplies only medroxyprogesterone, a progestin most closely related to bio-identical progesterone. DMPA suppresses ovarian estrogen levels. This results in some bone loss.
The second important information to know is that bone loss (called resorption) is normally in balance with building bone (called formation) in the bone renovation system that keeps bones healthy. However, bone resorption is fast and bone formation is slow. Therefore whenever bone resorption increases, as happens when estrogen levels drop with DMPA, bone loss occurs.
Third, medroxyprogesterone, like bio-identical progesterone, directly causes bone formation by making the osteoblast bone-forming cells work harder {Prior, 1990 1081 /id}. Bone density increased in women taking medroxyprogesterone pills for 10 days each month in a randomized, placebo-controlled study in young women with disturbances of cycles and ovulation {Prior, 1994 1859 /id}. Therefore DMPA, if bone loss is controlled, should build bone.
Although we have many studies showing that DMPA causes higher bone resorption and short term bone loss (Ott, 2001, JCEM) we now know that women gain bone when they stop using DMPA (Scholes Epidemiology 2002){Cundy, 1994 2497 /id}. Cross-sectional studies (measuring bone at one point in time) showed that bone density is not lower on DMPA except in the youngest women who were ages 18-21 (Scholes Obstet Gynecol 1999). However, in a study of women of all races, ages 14-18 on DMPA, the Pill or no contraception, bone density was not significantly lower in those on DMPA (Scholes Contraception 2004). Our best data suggests that after use and stopping of DMPA, bone density is eventually equal to or greater than those never on it.
So, knowing all of this, here’s what I suggest you do. First, if you could use barrier methods of contraception, I would strongly advise it. My reasons are that the normal maturation of menstrual cycles and ovulation is a long and complex process that any hormonal contraception interrupts. Second, today there is a potential to develop AIDS or other viruses—barrier methods are usually protective. Double barriers (condom or diaphragm plus jelly or foam) used every time are the most reliable contraception known and what I recommend. Furthermore, now emergency contraception is readily available and would be a short rather than long-term disruption of your ovulation and menstrual cycle.
Secondly, I’d strongly suggest that you follow the instructions in the “ABCs of Midlife Bone Health [1]” not because you are middle-aged! That article provides measures to prevent the high bone resorption that occurs normally during later perimenopause and in the first four years after menopause. That means get 2000 mg of elemental calcium, 1400 IU of vitamin D and half an hour of exercise every day. The protective effects of increased calcium and vitamin D for bone in DMPA users are currently being studied in controlled trials. You particularly should avoid colas and cigarettes, and limit coffee to two or three—these are all hard on bone. Also, your weight “on the heavy side” is protective for bone, so don’t diet to lose it. If you continue to be active (half an hour of walking or more every day), a slightly higher weight is not a health risk.
This long answer is to reassure you that DMPA is a reasonable choice for contraception. My ideal for all women, however, is that they develop a normal, ovulatory menstrual cycle. For that reason I would use two barrier methods if you can.
I hope this is helpful for you.
