Maintained bone density at advanced ages after long term treatment with low dose oestradiol implants.

OBJECTIVE

To investigate whether the bone preserving effect of low dose oestrogen replacement therapy (20 mg oestradiol implanted subcutaneously every six months) persists during continuous long term treatment through advanced ages.

DESIGN

Cross sectional clinical study of postmenopausal women treated with oestradiol implants as compared with nonusers matched for age.

SETTING

Outpatient research unit at a university hospital.

SUBJECTS

Thirty-five women with a mean age of 67 years (range 47-83 years) at the time of investigation who, after a prior hysterectomy, had been treated with oestradiol implants for climacteric symptoms for a mean period of 16 years (range 5.5-31 years). The results were compared with those in women matched for age and without any diseases or medications known to affect the bone metabolism.

MAIN OUTCOME MEASURES

Bone mineral densities (BMD) in the distal forearm, vertebrae and hip analysed by study group, age and duration of treatment.

RESULTS

Implant users had a median serum oestradiol concentration in the luteal range, 313 (range 126-1711) pmol/l, and premenopausal levels of follicle stimulating hormone (FSH). All women except one who were given the standard dose at the standard intervals had serum oestradiol levels below 650 pmol/l. Compared with nonusers, women treated with oestradiol implants had 20 to 25% higher BMD at all measurement sites: distal radius (P < 0.0001), lumbar vertebrae (P < 0.0002) and femoral neck (P < 0.0001). These differences also remained after adjustment for potential confounders (height, age at menarche, parity, smoking habits, physical exercise and education) (P < or = 0.01 at all sites). In a multiple regression analysis the negative effect of advancing age was more than compensated by the positive effect of increasing treatment duration with a higher BMD at all measurement sites in women with a longer as compared with shorter, duration of treatment; the regression coefficients were significant (P < 0.05) in the spine and hip measurements.

CONCLUSIONS

Continuous long term treatment with low dose oestradiol implants yielding physiological levels of serum oestradiol preserves both compact and cancellous bone and the effect seems to persist into advanced ages without any inevitable age related bone loss.