Is Bone Health at Risk for Adolescents on Birth Control?

A new review suggests that benefits continue to outweigh risks when it comes to preventing teen pregnancies

With Laura Bachrach MD

Adolescent girl

The percentage of teenagers engaging in sex has been trending down in recent years – at 40% in 2017 from a high of 47% in 2013. Most of those students are using some form of contraception, and the older they are, the more likely it is to be prescription birth control. But what is the impact on bone health for the girls who opt for hormonal methods to prevent pregnancy during adolescence? And given that girls use hormonal birth control for other reasons as well – including to help regulate heavy periods and hormonal acne – that question is of importance to a significant percentage of girls in their teens today.

While the use of most hormonal contraception in mature women has no demonstrated negative impact on bone health, there is some past evidence that seemed to suggest that in adolescents, it could be problematic in some cases, possibly impairing a still developing body’s ability to lay down more bone mineral at a time when girls are nearing peak bone mass.

A new study offers some reassurance to those young women, their parents, and their physicians that they can prevent pregnancy without worrying about bone health decades later. It also offers caution regarding using hormonal contraception in those years for other reasons, such as to moderate heavy periods and acne.

According to the new report, author Laura Bachrach, MD, a pediatric endocrinologist at Stanford University, found that combined oral contraceptives used by girls during their adolescence can reduce the amount of bone mineral deposited during those years, especially if used up to three years after starting their periods. Teens using low-dose oral contraception also showed reduced bone mass compared to their counterparts who didn’t use combined oral birth control, and the impact appeared in contraceptives with dosages ranging from 15 to 35 mcg of ethenyl estradiol. Based on the multicenter trial, it didn’t appear to matter what formulation of combined oral contraceptives were used, the users laid down less bone mineral than the control group.

Bachrach’s report found little data related to hormonal transdermal patches in teens, One study found that while there was no bone loss among the uses of the patch containing both estrogen and progestin, users didn’t gain bone compared to their counterparts. There is a similar lack of data related to progestin only contraceptive drugs, she noted. However, with DMPA, an intramuscular shot given every 12 weeks, there is a decrease in bone at the 150 mg dose, but not at the 75 mg. This occurs in women of every age using the method, but the loss is greater among teens. Studies show the loss is mostly or even completely reversible when users stop the medication.

Long-acting reversible contraceptive devices like intrauterine devices (IUDs), are increasingly used as the first-line contraception for teens. The limited data on bone health in adolescents and these devices implies that they don’t inhibit bone gain, and longer-term studies with mature women show no damage to bone health.

The use of oral contraceptives as an effort to protect the bones of young women who suffer from anorexia and for athletes who are amenorrheal has had mixed results. Some studies have shown their use is protective of bones, others that it does nothing positive. However, there is evidence that transdermal estrogen can help these patients improve and protect bone mass.

Bachrach says she has been interested in pediatric bone health for a long time, but the knowledge base was lacking. “Someone needed to be a scholar and delve into this,” she says. “There are tremendous holes in what is there that don’t take into account newer methods of birth control, like the long-acting reversible methods that were not around when I was a medical student. I approached this as an opportunity to learn something new.”

What she found is that there are not a lot of clear answers. “The findings that exist are not perfect, but there are many who read it and are very alarmed by the bone density data.” Bachrach herself is less worried.

There are greater risks to the health and well-being of young women from unplanned pregnancies than from a bone health perspective, she says. “If you are prescribing something for contraception, that’s a pretty important benefit. If it’s for other reasons, well, I’m more ambivalent.”

The kind of work that might provide definitive answers is expensive. There are researchers who are actively looking for grants to pay for prospective studies that would look long term at the bone health of young women who take hormonal birth control and follow them through the years to determine fracture risk later in life, or – perhaps more likely – at serial bone scan results that show progression from the time they start using the contraception to post-menopause, seeing how their bone density compares to control groups who didn’t use hormonal contraception. But that information is not available yet. “We have that kind of information for birth control pills. It would be great to have it for long acting contraception.”

In the interim, Bachrach says she tries to weigh the risks and benefits of a particular patient. “In an ideal world, I’d try something non-hormonal, but the failure rate for a younger teen might be high in terms of practice. If they are using the pill, there is a relatively higher failure rate. So there is great appeal for long-acting reversible options.”

For doctors and patients looking for reassurance related to using hormonal contraceptive methods, she says to consider the fact that, "Peak bone mass is reached by the early 20s, with 95% or so laid down by the age of 18. Most girls who are sexually active and on oral contraceptives are fairly far along toward their peak.”

Bacharach suggests that adolescent patients avoid hormonal medications as much as possible for other issues. “Try not to use something systemic. If you are using hormone therapy, lean heavily to using the 30 microgram dose. The 20 microgram dose may make for lighter periods, but isn’t as good for bones.”

In her opinion, long-acting contraception is a first choice treatment only for preventing pregnancy at this age, she adds. “And make sure those patients get enough calcium and are counseled about the dangers of smoking. You can offer these precautions and other recommendations as well for the future health of a young woman.”

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