Prevention of post-oophorectomy bone loss with tibolone
The results of a 1-year placebo-controlled study in 25 women who had hysterectomy and bilateral oophorectomy receiving a daily oral dose of 2.5 mg of Tibolone (Org OD 14) are presented. Tibolone is a steroid compound with mild oestrogenic in additional to progestagenic effects. Post-oophorectomy bone loss has been reported to accelerate, at least during the first year after surgery. The efficacy of Tibolone to prevent this accelerated bone loss is questionable. All patients were scheduled to participate in the study before oophorectomy. Patients had a detailed pre-operative examination, including measurement of forearm bone density with an SP2 Lunar single photon absorptiometer and haematological and biochemical investigation. After surgery, patients were randomly allocated in two groups; 15 women received an oral dose of 2.5 mg of Tibolone and 1000 mg of Calcium, while 10 women had only 1000 mg of calcium daily. Patients were examined at the end of 6 and 12 months of observation. Bone density of the radial shaft was found to decrease significantly in the calcium group up to 6.12% (P < 0.01) at the end of 6 months and 12.4% (P < 0.001) at the end of 12 months. On the other hand, bone density of the radial shaft remained unchanged in the Tibolone-treated group during the 12 months of treatment. Bone density of the distal radius was found to decrease in the calcium-treated group up to 10.2% (P < 0.014) at the end of 6 months and up to 15.8% (P < 0.002) at the end of 12 months. Bone density of the distal radius remained almost unchanged in the Tibolone-treated group during the whole period of treatment. Urine hydroxyproline/creatinine ratio was found to increase in the calcium group at the end of 6 and 12 months (P < 0.009) and to decrease significantly (P < 0.05) in the Tibolone-treated group. It is concluded that Tibolone is effective in the prevention of the post-ovariectomy accelerated bone loss and in retaining the initial premenopausal bone mass, at least during the first post-oophorectomy year. As this period is the most crucial in developing osteoporosis, it seems that Tibolone is effective in preventing the post-oophorectomy bone loss. HRT is not obligatory in these patients, as Tibolone seems to cover the whole spectrum of post-oophorectomy consequences.