The effect of oestradiol implants on regional and total bone mass: a three-year longitudinal study

Overview on the effects of progestins on bone

In view of the fact that fractures are the clinically relevant events, risk factors for fractures are discussed first. Bone mineral density (BMD) appears to be a much less important risk factor for the most severe hip fractures than the risk of falling. No results of experimental studies on hormones and fractures at advanced age are available. An overview of the effects of progestins on bone is given. Effects of progestins on bone have been studied by in vitro experiments using cell lines and by more relevant clinical observations. Prospective studies have been conducted following the use of progestins contained in oral contraceptives, alone or in combination with oestrogens; long-term contraception by injection of depot preparations; so-called "add-back" hormonal therapy attempting to reverse the adverse effects of gonadotropin releasing hormone agonists on bone and after different regimens of hormone replacement therapy (HRT) in postmenopausal women. From the data there are no indications that the various progestins, used in clinical practice, have either a bone-protective or an oestrogen antagonistic activity. Progestins do not add or subtract much of the protective action of oestrogens on the bones.

Hormone replacement therapy and fractures in older adults

Estrogen deficiency in women is associated with accelerated bone loss, and estrogen replacement therapy has been proven to be effective in preventing osteoporosis and fractures in postmenopausal women. The introduction of selective estrogen receptor modulators that have an estrogen-like effect on the skeleton but have a different pattern of effects on other tissues may have an important role in the management of osteoporosis in women in the near future. In men, androgen deficiency has been shown to be associated with osteoporosis. Although androgen replacement in hypogonadal men may decrease bone resorption and increase bone mass, long-term placebo-controlled trials are needed to better define the benefits and risks of such therapy before it can be recommended. Sex hormone deficiency is linked to the development of osteoporosis in both women and men. In women, hormonal replacement by estrogen or the newly developed selective estrogen receptor modulators may prevent the development of osteoporosis and its related fractures. In men, there is early evidence that testosterone replacement therapy may enhance bone mass in hypogonadal men.

Sex steroids and bone

Sex steroids are essential for skeletal development and the maintenance of bone health throughout adult life, and estrogen deficiency at menopause is a major pathogenetic factor in the development of osteoporosis in postmenopausal women. The mechanisms by which the skeletal effects of sex steroids are mediated remain incompletely understood, but in recent years there have been considerable advances in our knowledge of how estrogens and, to a lesser extent androgens, influence bone modeling and remodeling in health and disease. New insights into estrogen receptor structure and function, recent discoveries about the development and activity of osteoclasts, and lessons learned from human and animal genetic mutations have all contributed to increased understanding of the skeletal effects of estrogen, both in males and females. Studies of untreated and treated osteoporosis in postmenopausal women have also contributed to this knowledge and have provided unequivocal evidence for the potential of high-dose estrogen therapy to have anabolic skeletal effects. The development of selective estrogen receptor modulators has provided a new approach to the prevention of osteoporosis and other major diseases of menopause and has implications for the therapeutic use of other steroid hormones, including androgens. Further elucidation of the mechanisms by which sex steroids affect bone thus has the potential to improve the clinical management not only of osteoporosis, both in men and women, but also of a number of other diseases related to sex hormone status.

Are high levels of oestradiol after implants associated with features of dependence?

OBJECTIVE

To determine whether features of dependence develop in women receiving oestradiol implants, and if so, whether these features are related to serum oestradiol levels.

DESIGN

A questionnaire survey of women attending for implants over a six month period.

SETTING

An implant clinic in a district general hospital.

MAIN OUTCOME MEASURES

Psychological symptoms and their relationship to serum oestradiol levels.

RESULTS

Women with serum oestradiol levels below 500 pmol/L were generally asymptomatic of psychological symptoms.

CONCLUSION

Serum oestradiol levels of women receiving implants should be kept in the range of 300-500 pmol/L. Higher levels appear to be associated with the development of psychological symptoms which could be classified as features of dependence.

Does estrogen stimulate osteoblast function in postmenopausal women?

How estrogen therapy influences bone metabolism in postmenopausal women has previously been studied using several approaches, including bone densitometry, measurement of biochemical markers of bone turnover, and histomorphometry. Taken together, these investigations suggest that conventional doses of estrogen protect from bone loss predominantly through suppression of bone resorption, with little evidence to suggest that a stimulatory action on osteoblasts is also involved. In contrast, studies of patients treated with estradiol implants suggest that, following prolonged exposure to relatively high estrogen levels, an additional stimulatory effect on osteoblast function is observed. The suggestion that estrogen stimulates osteoblast activity in postmenopausal women under certain circumstances is consistent with other evidence that estrogen is an important physiological regulator of osteoblast activity. Furthermore, these findings raise the possibility that it may be useful to develop strategies for treating postmenopausal osteoporosis that aim to reproduce the stimulatory action of relatively high estrogen levels on bone formation in postmenopausal women.

Hormone replacement therapy

Oestrogen deficiency at the menopause leads to bone loss primarily as a result of increased bone turnover and an increase in the activity of osteoclasts. Hormone replacement therapy (HRT) reverses these changes, preventing menopausal bone loss and reducing fracture risk at the spine, hip, and wrist, although the magnitude of this reduction has not been accurately established. The optimal duration of therapy for the prevention of osteoporosis is uncertain but there is increasing evidence that life-long treatment after the menopause may be required to maintain maximum protection against fracture. The extraskeletal effects of long-term oestrogen therapy include protection against cardiovascular disease and a possible increase in the risk of breast cancer; the persistence of these effects after therapy is withdrawn is uncertain although there is some evidence that the increase in risk of breast cancer is seen only in current users. Furthermore, there is increasing evidence that the use of progestogens in combined formulations does not substantially alter either the cardiovascular benefits or the increased risk of breast cancer, although further studies are needed in this area. The emergence of 'no-bleed' preparations in recent years has increased the acceptability of HRT for some women, particularly those in older age groups. Finally, the development of tissue-selective oestrogen agonists is an exciting advance which may enable life-long therapy after the menopause to protect against cardiovascular and bone disease in the absence of significant side-effects.

Prevention of postmenopausal bone loss using tibolone or conventional peroral or transdermal hormone replacement therapy with 17beta-estradiol and dydrogesterone

Postmenopausal bone loss can be prevented by continuous or intermittent estradiol (E2) administration. Concomitant progestogen therapy is mandatory in nonhysterectomized women to curtail the risk of endometrial hyperplasia or cancer. However, the recurrence of vaginal bleeding induced by sequential progestogen therapy in addition to continuous estrogen administration is one of the reasons for noncompliance to hormone replacement therapy (HRT). Tibolone, a synthetic steroid with simultaneous weak estrogenic, androgenic, and progestational activity, which does not stimulate endometrial proliferation, has recently been proposed for the treatment of climacteric symptoms. To compare the efficacy of conventional oral and transdermal HRT with that of tibolone in the prevention of postmenopausal bone loss, 140 postmenopausal women (age, 52 +/- 0.6 years; median duration of menopause, 3 years) were enrolled in an open 2-year study. Volunteers had been offered a choice between HRT and no therapy (control group, CO). Patients selecting HRT were randomly allocated to one of the following three treatment groups: TIB, tibolone, 2.5 mg/day continuously, orally; PO, peroral E2, 2 mg/day continuously, plus sequential oral dydrogesterone (DYD), 10 mg/day, for 14 days of a 28-day cycle; TTS, transdermal E2 by patch releasing 50 microg/day, plus DYD as above. Bone densitometry of the lumbar spine, upper femur, and whole body was performed using dual-energy X-ray absorptiometry at baseline, and then 6, 12, 18, and 24 months after initiation of therapy. One hundred and fifteen women (82%) completed the 2 years of the study. The dropout rate was similar in each group. Over 2 years, bone preservation was observed in all three treatment groups as compared with controls, without significant differences among treatment regimens. In conclusion, tibolone can be regarded as an alternative to conventional HRT to prevent postmenopausal bone loss.