We are aware of the potential for loss of bone mineral density (BMD) with Depo-Provera, but what effect, if any, do other hormonal methods of contraception have? A systematic review was published in 2006 which looked at the effects of oral contraceptives on BMD, and another study looked at BMD in users of the intra-uterine system (IUS) compared to the intra-uterine device (IUD).
Hormonal methods of contraception are highly effective and widely used. These methods have important health benefits and risks. For most women, the health benefits exceed the risks.
There is a known association between oestrogen metabolism and bone turnover. The issue of hormonal methods effecting BMD may be of particular importance to adolescent and perimenopausal users of these methods.
The principal clinical outcome of interest with regard to bone health is the occurrence of fracture. Fracture risk is related to many factors, BMD being only one of them. BMD is often used as a surrogate end point as an outcome measure that can be clinically measured, substituting for the clinical outcome of fracture.
The relationship between decrease in BMD and increase in fracture risk has been studied in postmenopausal women, but there is little information on the link, if any, in premenopausal women. In response to the questions raised regarding use of Depo-Provera and the risk of loss of BMD, the World Health Organization (WHO) convened a consultation to assess the current evidence on the relationship between the use of hormonal methods of contraception and bone health.
A systematic review published this month appraised 75 articles on the effect of oral contraceptives and other hormone replacement on BMD. The evidence was appraised using the Oxford Centre for Evidence-Based Medicine levels of evidence.
The review looked at the effects for four groups of women
Healthy premenopausal women
All four randomised controlled trials (RCTs) showed no effect on BMD as measured by dual energy x-ray absorptiometry (DEXA) or computerised tomography (CT), but three of the four showed a positive effect on bone turnover.
Oligo/amenorrhoeic premenopausal women
In all studies that compared baseline BMDs of oligo/amenorrhoeic women with controls, baseline BMD was higher in the controls.
Anorexic premenopausal women
The effect of oestrogen on increasing BMD was greatest in the women with lowest body weights.
Perimenopausal women
The evidence for increasing BMD with the COC was most convincing for this group.
The following table shows the studies reviewed for each of the four groups and whether they showed a positive effect, no effect or a negative effect. The number in brackets is the total number of women in these studies.
| Total studies reviewed | Positive effect | No effect | Negative effect | |
|---|---|---|---|---|
| Healthy | 46 (15588) | 10 (6503) | 29 (7724) | 7 (1361) |
| Oligo/amenorrhoeic | 10 (444) | 7 (379) | 2 (64) | 1 (1) |
| Anorexic | 8 (734) | 2 (483) | 5 (247) | 1 (4) |
| Perimenopausal | 11 (6739) | 8 (5854) | 3 (885) | 0 (0) |
This review did not look at the adolescent group in particular. A review published in August 2005 suggested that the use of low dose 20 mcg COC pills may reduce the peak BMD, particularly when started within the adolescent period. The impact of other hormonal contraceptive methods on bone health appears to be correlated with the degree of suppression of oestrogen levels.
WHO's conclusion was that with regard to bone health there should be no restriction on the use of combined hormonal contraceptive methods among women who are otherwise eligible to use these methods, including no restrictions on duration of use.
The Clinical Effectiveness Unit (CEU) of the Faculty of Family Planning and Reproductive Health Care (FFPRHC) of the Royal College of Obstetricians and Gynaecologies (RCOG) comment that there is no evidence at the present time to suggest that the POP Cerazette has any effect on bone mass density. However they acknowledge the distinct lack of evidence in the literature. A study from 1994 showed that the POP may reduce the lactation related loss of BMD in the first year post-partum.
The National Institute for Clinical Evidence (NICE) reported "there is no evidence of an effect of Implanon use on bone mineral density".
Implanon inhibits ovulation for all women in the first two years of use, but endogenous oestrogen is maintained, so there is no oestrogen deficiency, and it is likely this is why there is no effect on BMD. This is in comparison to Depo-provera, where it is known that serum oestrogen levels are reduced.
A cross-sectional study looked at forearm BMD in a group of 53 IUS users compared with 53 IUD users. Women were paired by age (+/- 1 year) and body mass index (+/-1). BMD was measured in the forearm by use of DEXA scanning. The results showed that the mean BMD was very similar in both groups. This conclusion of no effect of the IUS on BMD is supported by the FFPRHC. NICE did not comment on bone health related to the IUS in its recent review of long acting reversible methods of contraception (LARCs).
WHO concluded that with regard to bone metabolism there should be no restriction on the use of progestogen-only contraceptive methods (other than Depo-Provera) among women who are otherwise eligible to use these methods, including no restrictions on duration of use.