Variations on HRT.
Low Bone Density
Although the new non hormonal therapies for low bone density are currently
more in favour there is still a place for oestrogen therapy which is
the only treatment which has been shown to decrease the risk of both
vertebral and hip fractures. Oestrogens are anabolic as well anti-catabolic
to the bone and are most effective in older women or in women with an
osteoporotic skeleton. The increase of bone density with oestrogens
is dose dependent with a positive correlation between plasma oestradiol
levels and bone density. There is also a correlation between oestradiol
levels and histomorphometric changes of wall thickness, trabecular volume
and new formation of matrix collagen (17). No such data exists for bisphosphanates.
Plasma oestradiol levels of 300pmols/L are necessary for an increase in bone density in most patients. But as most North American patients are prescribed conjugated equine estrogens, estradiol measurements have not been a feature of American practice’.
The advice from the regulatory authorities that estrogens should not be first line therapy for the prevention or treatment of osteoporosis particularly in otherwise healthy women under the age of 60 has been questioned (34). Regrettably there has always been a conflict, almost a “turf war” between bone physicians for whom the side effects of bleeding, mastalgia and PMS symptoms with progestogen is uncharted territory and gynaecologists who are more familiar with the problems of gonadal hormones. This has been reinforced by Banks et al (35) of the MWS who claim that on cessation of estrogen therapy bone density “rapidly” reverted to pre-treatment levels. This has been disputed, (36 37) but it does further demonstrate the design problem of this study which relied upon a single questionnaire. In reality ten years of moderately low dose estrogen therapy will increase the vertebral bone density by approximately 10% It is both counter-intuitive and certainly against clinical observations that this benefit is rapidly lost .However it is used as further justification to use non hormonal therapy as first choice or to discontinue this therapy after a short course of estrogens in these younger women in spite of the added quality of life benefits of hormone therapy.