Bone mineral density of the lumbar spine in endometriosis subjects compared to an age-similar control population

Bone mineral density in women with deep infiltrating endometriosis who have undergone early bilateral oophorectomy

OBJECTIVE

To study bone mineral density (BMD) in women with and without pelvic deep infiltrating endometriosis (DIE) who underwent early bilateral oophorectomy (BO).

METHODS

A case-control study was performed in 83 women who underwent early BO before the age of 45 years, 31 for DIE and 52 for another clinical condition. All the women answered a standardized computer-assisted questionnaire to record their clinical and historical data and were medically examined. Lumbar spine and femoral neck BMDs were measured by dual-energy X-ray absorptiometry after early BO. Simultaneously, serum calcium, intact parathyroid, 25-hydroxyvitamin D, and cross-linked C-telopeptide were also measured. Unadjusted and adjusted odds ratios (with 95% confidence intervals [CI]) for endometriosis were calculated using logistic regression.

RESULTS

The mean lumbar spine and femoral neck BMDs were significantly higher in women who underwent early BO for DIE than in those who underwent early BO for another clinical condition. After adjusting for age at BMD measurement, years since menopause, age at menarche and body mass index, odds ratio for endometriosis associated with a 1-SD increase in lumbar spine and femoral neck BMD was 2.59 (95% CI: 1.45-4.62) and 2.16 (95% CI: 1.23-3.81), respectively.

CONCLUSION

Higher lumbar spine and femoral neck BMDs are associated with an increase in the likelihood of pelvic DIE in women who underwent early BO. This might be expected to the extent that endometriosis is itself associated with enhanced estrogen status, although further studies are needed to confirm such a hypothesis. These findings suggest that BMD measurement could contribute to the hormonal management of surgical menopause in women with DIE.

Gonadotrophin-releasing hormone analogues for endometriosis: bone mineral density

BACKGROUND

Gonadotrophin-releasing hormone analogues (GnRHas) are generally well tolerated, and are effective in relieving the symptoms of endometriosis (Prentice 2003). Unfortunately the low oestrogen state that they induce is associated with adverse effects including an acceleration in bone mineral density (BMD) loss.

OBJECTIVES

To determine the effect of treatment with gonadotrophin-releasing hormone analogues (GnRHas) on the bone mineral density of women with endometriosis, compared to placebo, no treatment, or other treatments for endometriosis, including GnRHas with add-back therapy.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group's specialised register of controlled trials (23rd October 2002) and the Cochrane Central Register of Controlled Trials (Cochrane Library, issue 4, 2002). We also carried out electronic searches of MEDLINE (1966 - March Week 2 2003) and EMBASE (1980 - March Week 2 2003). We also searched the reference lists of articles and contacted researchers in the field.

SELECTION CRITERIA

Prospective, randomised controlled studies of the use of GnRHas for the treatment of women with endometriosis were considered, where bone density measurements were an end point. The control arm of the studies was either placebo, no treatment, another medical therapy for endometriosis, or GnRHas with add-back therapy.

DATA COLLECTION AND ANALYSIS

Two reviewers (JF and MS) independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Thirty studies involving 2,391 women were included, however only 15, involving 910 women, could be included in the meta-analysis. The meta-analysis showed that danazol and progesterone + oestrogen add-back are protective of BMD at the lumbar spine both during treatment and for up to six and twelve months after treatment, respectively. Between the groups receiving GnRHa and the groups receiving danazol/gestrinone, there was a significant difference in percentage change of BMD after six months of treatment, the GnRH analogue producing a reduction in BMD from baseline and danazol producing an increase in BMD (SMD -3.43, 95 % CI -3.91 to -2.95). Progesterone only add-back is not protective; after six months of treatment absolute value BMD measurements of the lumbar spine did not differ significantly from the group receiving GnRH analogues (SMD 0.15, 95 % CI -0.21 to 0.52). In the comparison of GnRHa versus GnRHa + HRT add-back, that is oestrogen + progesterone or oestrogen only, there was a significantly bigger BMD loss in the GnRHa only group (SMD -0.49, 95 % CI -0.77 to -0.21). These numbers reflect the absolute value measurements at the lumbar spine after six months of treatment. Due to the small number of studies in the comparison we are unable to conclude whether calcium-regulating agents are protective. No difference was found between low and high dose add-back regimes but again only one study was identified for this comparison. Only one study comparing GnRH analogues with placebo was identified, but the study gave no data. No studies comparing GnRH with the oral contraceptive pill (OCP) or progestagens were identified.

REVIEWER'S CONCLUSIONS

Both danazol and progesterone + oestrogen add-back have been shown to be protective of BMD, while on treatment and up to six and 12 months later, respectively. However, by 24 months of follow-up there was no difference in BMD in those women who had HRT add-back. Studies of danazol versus GnRHa did not report long-term follow-up. The significant side effects associated with danazol limit its use.

A meta-analysis of the effects of cigarette smoking on bone mineral density

To determine the magnitude and mediators of the association between cigarette smoking and bone mass in the epidemiologic literature we reviewed articles, published abstracts, and conference proceedings, identified through MEDLINE, psychological abstracts, conference proceedings, and article bibliographies. We studied cross-sectional and prospective human studies that provided a quantitative measure of bone mass (X-ray, absorptiometry, or computed tomography) as a function of cigarette smoking exposure. Effects were expressed as pooled standardized mean differences for categorical comparisons (e.g., bone mass in current versus nonsmokers), and as pooled correlation coefficients for continuous comparisons (e.g., correlation of bone mass and pack-years of smoking). Effects were derived for combined bone sites (all bone sites pooled within each study) and four specific sites (hip, lumbar spine, forearm, and os calcis), and were examined overall and as a function of subject and methodologic characteristics (gender, age, body weight, menopausal status, health status). Data were pooled across 86 studies, enrolling 40,753 subjects. Smokers had significantly reduced bone mass compared with nonsmokers (never and former smokers) at all bone sites, averaging a one-tenth standard deviation (SD) deficit for combined sites. Deficits were especially pronounced at the hip, where the bone mass of current smokers was one-third of a SD less than that of never smokers. Overall, effects were greatest in men and in the elderly, and were dose-dependent. In prospective studies, smokers had greater rates of bone loss over time compared with nonsmokers. Bone mass differences remained significant after controlling for age and body weight differences between the two groups. Absolute effect sizes at most bone sites were greatest for current smokers compared with never smokers, intermediate for current smokers compared with former smokers, and lowest for former smokers compared with never smokers, suggesting that smoking cessation may have a positive influence on bone mass. Based on these data, it is estimated that smoking increases the lifetime risk of developing a vertebral fracture by 13% in women and 32% in men. At the hip, smoking is estimated to increase lifetime fracture risk by 31% in women and 40% in men. It appears that smoking has an independent, dose-dependent effect on bone loss, which increases fracture risk, and may be partially reversed by smoking cessation. Given the public health implications of smoking on bone health, it is important that this information be incorporated into smoking prevention and cessation efforts.

Surgically induced endometriosis attenuates accrual of bone mineral density in growing rats

OBJECTIVE

A possible association of endometriosis with decreased bone mineral density in women has been proposed. It has been reported that cortical and trabecular bone mass of the distal portion of the radius is decreased in patients with endometriosis. The objective of this study was to investigate the relationship between endometriosis and bone mineral density with the use of a rat model.

STUDY DESIGN

Cycling female Sprague-Dawley rats (180 days old) were randomly assigned to 1 of 2 groups. The treatment group (n = 16) underwent surgical induction of endometriosis. Female rats (n = 17) with surgically transplanted abdominal muscle served as control animals. Dual-energy x-ray absorptiometry measurements were obtained before surgery and after 90 days with a Lunar DPX-MD+ (GE Lunar, GE Medical Systems, Milwaukee, Wis) bone densitometer, with software standardized for small animal research.

RESULTS

Experimental animals had grossly visible endometriotic disease at necropsy (90 days). The mean net change in total bone mineral density from baseline to 90 days in the control group was +0.019 +/- 0.002 g/cm2, whereas the mean net change in total bone mineral density for the experimental group was +0.013 +/- 0.002 g/cm2. The experimental group gained less bone than the control group (P = .02).

CONCLUSION

The age-appropriate increase in bone mineral density known to occur in this animal model is attenuated by surgically induced endometriosis. This finding supports the idea that endometriosis might be associated with decreased bone mineral density.

Women of reproductive age with endometriosis are not osteopenic

OBJECTIVE

To determine whether women of reproductive age with endometriosis are osteopenic and whether bone density decreases with higher stages of endometriosis.

DESIGN

A multicenter cross-sectional study was performed.

SETTING

Thirty-nine gynecological clinics in the United States, Canada, and Puerto Rico.

PATIENT(S)

Two hundred forty-one women of reproductive age with laparoscopically proved endometriosis.

INTERVENTION(S)

Diagnostic laparoscopy, bone densitometry.

MAIN OUTCOME MEASURE(S)

Endometriosis stages according to the criteria of the American Society for Reproductive Medicine, lumbar spine bone mineral density (L2-L4) as measured by dual-energy x-ray absorptiometry.

RESULT(S)

The mean lumbar spine bone mineral density, as well as the distribution of bone mineral density, of the women with endometriosis was similar to that of a normal population. There were no significant differences between endometriosis stage groups I-IV regarding bone mineral density as well as body weight, body mass index, and height.

CONCLUSION(S)

Women of reproductive age with endometriosis are not osteopenic. More advanced stages of endometriosis are not associated with a decrease in lumbar spine bone mineral density.

The impact of bone loss in women with endometriosis

Low peak adult bone mass in a premenopausal woman puts her at increased risk for osteoporosis postmenopausally. Episodes of hypo-estrogenism premenopausally are associated with loss of bone density. This is seen with gonadotropin-releasing hormone agonist therapy for endometriosis, and thus prolonged or repeated courses of such treatment may increase the future risk of osteoporosis. Danazol and related compounds do not result in any bone loss but may have certain metabolic disadvantages.

Bone loss during gonadotropin releasing hormone agonist treatment and use of nasal calcitonin

Gonadotropin releasing hormone (GnRH) agonists have shown to be effective in the treatment of several sex-hormone-dependent conditions. However, their use could be limited by the bone loss they induce. To evaluate the use of nasal salmon calcitonin (sCT) in preventing this bone loss, 40 patients with endometriosis were treated for 6 months with triptoreline (3.75 mg monthly) and calcium (1 g daily), and randomized in three groups-placebo, sCT 100 IU daily and sCT 200 IU daily-in a prospective double-masked study. Dual-energy X-ray absorptiometry and biochemical parameters were used to evaluate the benefit of the treatment. At baseline, there were no statistically significant differences between the groups. After 6 months, estradiol and biochemical markers of bone metabolism were at postmenopausal levels, with no difference between the groups. There was no difference in bone loss in the three groups, at all sites. Mean lumbar bone loss was 4.01 +/- 2.59% (mean +/- SD) in this population. In this study dosages of 100 IU and 200 IU daily of nasal sCT were insufficient to prevent bone loss during GnRH agonist treatment.

Parathyroid hormone for the prevention of bone loss induced by estrogen deficiency

BACKGROUND

Analogues of gonadotropin-releasing hormone (GnRH) are often given to induce hypogonadism in women who have estrogen-dependent disorders such as endometriosis and uterine leiomyomas. Because estrogen deficiency causes bone loss, concern about premature osteoporosis has prevented long-term therapy with GnRH analogues. We conducted a study to determine whether parathyroid hormone could prevent bone loss in women receiving therapy with GnRH analogues.

METHODS

We administered human parathyroid hormone (40 micrograms subcutaneously daily) to 20 of 40 women with endometriosis who were being treated with nafarelin (200 micrograms intranasally twice daily) for six months; the remaining 20 women received only nafarelin. Cortical and trabecular bone density and biochemical markers of bone turnover were measured every three months during the six-month study period.

RESULTS

Serum estradiol concentrations fell to postmenopausal values in 36 of the 40 women. In the women who received nafarelin alone, the mean (+/- SE) bone density in the lumbar spine decreased by 2.8 +/- 0.5 percent (P < 0.001) when measured in the anteroposterior projection and by 3.5 +/- 0.8 percent (P < 0.001) when measured in the lateral projection. In contrast, bone density in the lumbar spine did not change when measured in the anteroposterior projection and increased by 3.4 +/- 1.2 percent when measured in the lateral projection (P = 0.01) in the women who also received parathyroid hormone. Bone density at the femoral neck decreased slightly and similarly in both groups. Radial bone density did not change in either group. Serum alkaline phosphatase and osteocalcin concentrations and urinary hydroxyproline and pyridinoline excretion increased (P < 0.001) in the women who received nafarelin plus parathyroid hormone.

CONCLUSIONS

Parathyroid hormone can prevent bone loss in the lumbar spine in young women with estrogen deficiency caused by treatment with GnRH analogues.

Bone density and endometriosis

To establish whether there is evidence of low bone density in women with endometriosis, we compared bone density between 48 women with laparoscopically proven endometriosis and 48 age-matched normal controls. Bone density of the lumbar spine (L2-4), proximal femur (femoral neck, Ward's triangle, and trochanteric region), and total body were measured by dual energy roentgenogram absorptiometry. After adjusting for physical and lifestyle differences, bone density was not significantly different between the groups in any site. Bone density measurements were not related to the severity of endometriosis. These results do not confirm evidence of low bone density in women with endometriosis.

Impact of medical treatment of endometriosis on bone mass

A review of studies examining the effect of medical therapy of endometriosis on bone mass and potential approaches to preventing bone loss was undertaken. Studies specifically examining bone density in women with endometriosis treated medically were used. Reports on effects of oral contraceptives and progestins on bone mass were derived from women using them for contraception. Oral contraceptives and medroxyprogesterone acetate apparently did not adversely affect bone mass. While initial studies with dual-photon absorptiometry were unable to detect appreciable bone loss with gonadotropin-releasing hormone agonist, subsequent studies have invariably found significant bone loss beginning as early as 3 months of treatment. Quantitated computerized tomography always shows significant trabecular bone loss of the vertebrae and hip with gonadotropin-releasing hormone agonist. Depot preparations appear to produce more marked loss than daily injections of intranasal spray. Recent studies indicate recovery of bone loss may take longer than 6 months or even 1 year after discontinuation of therapy with considerable individual variation. Danazol produced bone gain. Bone loss with gonadotropin-releasing hormone agonists could be prevented or attenuated with progestins, and this is worthy of further studies. Impact of medical therapy on bone mass should be a practical consideration in the selection of patients, in repeat medical therapy for recurrence of endometriosis, and in formulation of medical therapy so as to attenuate or overcome such silent adverse effects.

Gonadotropin-releasing hormone agonists and the skeleton

OBJECTIVE

To review and evaluate published studies that have assessed the effect on the skeleton of treatment with gonadotropin-releasing hormone agonists (GnRH-a). The effects on bone biochemistry and bone density are presented.

DATA IDENTIFICATION

Major studies reporting on bone and GnRH-a use were identified through Excerpta Medica and Medline searches.

STUDY SELECTION

Those that have reported on GnRH-a treatment in patients where data relating to skeletal metabolism or bone density were obtained.

RESULTS

Changes in bone biochemistry during GnRH-a therapy indicate that there is altered skeletal metabolism associated with GnRH-a use. The data on changes in bone density after a 6-month course of GnRH-a therapy generally indicate some bone loss. The magnitude of any detected change in bone density depends on the skeletal site assessed and the method of assessment. No significant bone loss has been documented in cortical bone; any bone loss occurring is usually associated with trabecular bone and is partially or completely reversible on withdrawal of GnRH-a treatment.

CONCLUSIONS

A 6-month course of GnRH-a therapy may result in a small reduction in trabecular bone density that is partially or completely reversible on withdrawal of treatment. The magnitude of any persistent residual bone loss is unlikely to be of clinical relevance and the benefits of a single 6-month course of GnRH-a therapy should not be withheld on the basis of a possible effect on bone.