Estrogen in Birth Control Pills May Affect Bone Health of CF Patients
Supplemental estrogen, most commonly taken for contraception, is associated with poorer bone mineral density in people with cystic fibrosis (CF), a new study suggests.
The study, “Oral ethinyl estradiol treatment in women with cystic fibrosis is associated with lower bone mineral density,” was published in the Journal of Clinical and Translational Endocrinology.
Oral contraceptive pills containing the hormone estrogen at low dose are commonly used to prevent pregnancy by women, including those with CF. However, estrogen not only affects the reproductive system; among its many roles in the body is regulating the growth and maintenance of bones.
Research has suggested that estrogen-containing contraceptives could reduce bone mineral density (BMD) — that is, how hard bones are — in the general population.
Low BMD is associated with an increased risk of bone fracture. This may especially be a concern in people with CF, who are already at a higher risk of bone disease. However, the effect of estrogen supplements on BMD in people with CF is not clear.
A team led by researchers at Emory University School of Medicine analyzed data on 49 premenopausal women with CF, ages 18 to 50, who had undergone bone mineral density evaluation as part of their routine care.
Twelve women were taking estrogen supplements at a mean dose of 23.3 micrograms (mcg) per day (range of 10–30 mcg/day). Of these, 11 were taking oral estrogen (pills), and one was taking estrogen vaginally. All were also taking progesterone, another hormone used for contraception. The average age of this group was 31.4 years, and 75% were Caucasian.
The other 37 patients had no recorded history of estrogen supplementation, although three of them were taking progesterone alone. Demographics between the two groups were similar: the average age in this non-estrogen group was 30.4 years, and 89% were Caucasian.
Results showed that the mean BMD of the lumbar (lower) spine was significantly lower in individuals who had taken estrogen (0.952 g/cm2)  compared to those not taking estrogen (1.023 g/cm2). A related measurement, BMD Z-score, was also significantly lower in those who had taken estrogen supplements (-0.7 vs. 0.04).
Similar trends were observed for the femur (thigh bone) and hips, though differences in BMD did not reach statistical significance in these locations. This is likely because “the lumbar spine is the most sensitive to sex hormone status,” the researchers wrote.
These results suggest a connection between estrogen-containing birth control and a lower BMD, although the researchers note that caution should be exercised in interpreting the findings of a single, relatively small study.
“Low-dose estrogen supplementation in premenopausal women with CF was associated with lower BMD, compared to no estrogen supplementation in a similar group of premenopausal young women with CF,” the researchers concluded, adding that “future studies are needed to investigate the optimal formulation, route of administration, and dose to accrue and preserve bone mass in premenopausal women with CF.”
They also recommended that “healthcare providers should be wary that standard oral contraceptives that contain estrogen may not be adequate for skeletal health in CF, and should monitor bone mineral density of their patients according to CF Foundation guidelines.”
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