Birth control pills are the most common means of preventing pregnancy in the US. The Pill is also prescribed for other reasons, including painful periods, irregular or heavy periods, premenstrual syndrome (PMS), migraine headaches, and acne. Birth control pills are a synthetic form of the hormones estrogen and progesterone. Over the past thirty years, the strength of hormones contained in the Pill has gradually decreased to lessen the risk of side effects such as blood clots.
The current lowest dose birth control pills contain 20 micrograms (mcg) of an estrogen called ethinyl estradiol in combination with another hormone called progesterone, which may vary according to different manufacturers and brands. It is common practice for doctors to prescribe these low-dose pills for women of all ages. Though low-dose pills may be good for thirty-something women through those making the menopausal transition, they are not good for teenagers and young adults.
Until recently, very little attention has been directed toward the effect of different doses of the Pill on bone growth during the teen years. In fact, many doctors who prescribe the low-dose 20 mcg pill are not aware of its potential harmful effects on bone mass. The Pill works by maintaining consistent estrogen and progesterone levels. Without the mid-cycle estrogen surge, the average monthly estrogen levels for pill users are significantly lower than those of women with regular cycles. These lower-than-average estrogen levels associated with low-dose birth control pills may not support normal bone growth. Sufficient estrogen is critical for optimal bone growth in the teen years and for attainment of peak bone mass.
LOW-DOSE PILL EFFECTS ON BONE DEPEND ON YOUR AGE
More than 40 percent of your bone mass accumulates during the teen years. In contrast, when you reach your thirties, you have reached your peak bone mass and have a slow steady loss of bone mass until the menopausal transition. For those reasons, growing teenagers need more estrogen support than older premenopausal women who have already reached their peak bone mass.
Teenagers and Young Women
Recent studies have scrutinized the pill dose of estrogen necessary for optimal bone growth in teenagers and young women. Researchers observed that young pill users had less increase in bone density compared with young women not using the Pill. Studies of the low-dose pill with 20 mcg of ethinyl estradiol cast doubt on its ability to support bone growth and the achievement of optimal peak bone mass.
Use of higher-dose birth control pills that contain 30 to 40 mcg of ethinyl estradiol has no demonstrated detrimental effects on bone density in teens and young women. There is consistent evidence that birth control pills containing 30 mcg of ethinyl estradiol are adequate to ensure sufficient bone accrual during adolescence and normal bone health into adulthood.
The research findings make sense if you think about how birth control pills work. The suppression of hormones with low-dose pills does not allow sufficient estrogen support for the growing skeleton, and this results in less bone mass. The impact of birth control pills is largest during the time of highest bone mass growth. Unfortunately, we do not have information about what happens after teenagers discontinue their use of low-dose pills. Questions remain about the use of low-dose birth control pills by teenagers and young adults. Are the negative effects on bone reversible after stopping the Pill? Is there a long-term risk for osteoporosis and fractures later in life?
It is important to ensure that teenagers and young women achieve the strongest bones possible. For this reason, it is best to limit the use of birth control pills or to use higher-dose pills instead of low-dose preparations. A gynecologist friend told me that a common request for the Pill comes from teens and their mothers for use in control of acne. Instead, she advises them to use local measures and, if needed, consider antibiotics. She says that when these same girls return later for an office visit, she often finds out that they are taking birth control pills that their dermatologists have prescribed, since acne is an indication for its use.
Please understand the implications of using low-dose birth control pills during the teen years. You do not want to jeopardize bone health. If the use of birth control pills is warranted, it is preferable to use preparations containing at least 30 mcg of ethinyl estradiol to ensure proper bone development.
Thirties and Forties (After Attaining Peak Bone Mass)
Premenopausal bone loss starts soon after attaining peak bone mass in the late twenties to early thirties. The rate of bone loss at the spine is estimated to be up to 1 percent each year. The dense bone sites, such as the hip and forearm, have much lower rates of loss. The low-dose birth control pills contain enough estrogen to prevent or slow bone loss, particularly at the spine.
Older studies show that bone density was protected using higher dose pills (30 to 40 mcg of estradiol) for five to ten years. Spine bone density may increase one percent for each year of use. The greatest protection of bone is seen with ten or more years of use of the higher dose pill.
Perimenopause
During the menopausal transition, or so-called perimenopause, women with irregular periods are more likely to lose bone than women who continue to have regular periods. No evidence of bone loss is seen in perimenopausal women who continue normal menstruation. Once menstrual periods become irregular due to low estrogen production during the transition to menopause, bone loss starts to accelerate; bone loss will typically be about 2 percent a year.
Perimenopausal women who use low-dose pills (20 mcg of ethinyl estradiol) can preserve and even increase their bone mass. The biggest effect is seen at the spine, which has the fastest bone metabolism. Without protection against bone loss, a long menopausal transition may signify an additional risk factor for low bone mass and osteoporosis. Low-dose pills make sense for the perimenopausal women, both for protecting the bone and preventing the “oops” baby.
The changes that occur in the bone at different ages should be an important consideration when determining which birth control pill to prescribe. Of specific importance is the estrogen content of the pills. Low-dose pills may be good for women over thirty through the menopausal transition, but they are not good for teenagers and young adults. Teens are not “little adults.” Pills with a higher dose of estrogen are needed for support of bone growth. However, low-dose pills may prevent bone loss in women who have attained peak bone mass, and they may even boost bone mass in perimenopausal women.
DEPO-PROVERA
Depo-Provera (depot medroxyprogesterone acetate) is another effective birth control method that contains only a type of progesterone. Depo-Provera is sometimes an appealing choice for women because it is a shot given every three months, so you don't have to worry about taking a pill everyday.
Depo-Provera prevents pregnancy by a different mechanism than the Pill. A slow release from the injection site provides the prolonged action. It stops the master gland of the body, the pituitary, from producing the messenger hormones that signal the ovary to release an egg during the middle of the normal menstrual cycle. As a result, a woman has no menstrual periods and has decreased production of estrogen.
Unfortunately, the effectiveness of Depo-Provera comes with a downside for the bone, particularly for teenagers and young adults. Use of Depo-Provera for two years is associated with an average bone loss of 6 percent at the spine and 5 percent at the hip in all ages of users. The longer the drug is used, the greater the bone loss. In teens, this loss may be due to lack of bone mass accrual rather than actual loss.
As a result of these research findings, in 2004 the FDA issued a prominent boxed warning in the product label, referred to as a “black box” or “boxed” warning, which can be found in the package insert for Depo-Provera. Because of the bone loss associated with Depo-Provera and the concern that it may not be completely reversible, the FDA recommended that use of Depo-Provera be limited to two years or fewer.
More recent studies indicate that the bone loss observed may be fully or at least partially reversible, with significant increases in bone density occurring after discontinuation. However, bone density improvements after stopping Depo-Provera may be blunted if Depo-Provera is followed by taking low-dose birth control pills. Limiting use of Depo-Provera to two years or fewer appears to be the best option for limiting bone loss.
Nevertheless, the American College of Obstetricians and Gynecologists in a 2008 Committee Opinion concluded that the need for effective birth control to prevent teenage pregnancies outweighs the risk of bone effects. They stated that when Depo-Provera is the best option to prevent pregnancy concerns regarding its effect on bone density “should neither prevent practitioners from prescribing Depo-Provera nor limit its use to two consecutive years.” Longterm use for reasons other than prevention of pregnancy should be avoided.
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The Bare Bones
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