Long-term progestogen treatment and bone remodelling in peri-menopausal women: a longitudinal study

In view of the potential adverse consequences of oestrogen treatment, the effects of a progestogen on bone mass and bone remodelling have been evaluated in a longitudinal study. Bone mass and bone remodelling were measured radiogrammetrically in 39 peri-menopausal women who participated in an earlier cross-sectional study and continued to receive progestogen treatment, viz. lynestrenol, 5 mg daily, for 4.5 yr after the first assessment. Follow-up data obtained in untreated peri-menopausal and post-menopausal women and in oestrogen-treated post-menopausal women were used for comparison purposes. Pairs of hand films were measured blind by the same observer. For each pair of films, the average over six metacarpals of periosteal and endosteal width, cortical thickness and cortical area was calculated. In the progestogen-treated group a slight increase in periosteal diameter occurred, comparable to the untreated and oestrogen-treated groups. The increase in endosteal diameter in the progestogen-treated group is half that in the untreated groups, with a resultant smaller loss in cortical thickness in the lynestrenol group as compared with the untreated controls. Although lynestrenol's effectiveness in inhibiting bone resorption seems to be similar to that of oestrogen, the effect is less than that observed in post-menopausal women treated with conjugated equine oestrogens (1.25 mg) or ethinyl oestradiol (0.025 mg).