Continuous oestrogen-progestogen treatment and bone metabolism in post-menopausal women

The suggestion that norethisterone acetate (NETA) stimulates bone formation prompted us to investigate calcium and bone metabolism in post-menopausal women treated with a continuous combination of oestrogen and NETA. The study included 49 healthy post-menopausal women. After an initial examination the women were randomly allocated to 2 yr of treatment with either hormones or placebo; 43 women completed the study. Within the first year of treatment the hormone group showed a slight, but significant, increase in bone mineral content in the forearms (single photon absorptiometry) and in the total skeleton (dual photon absorptiometry). After this initial increase the bone mass remained constant throughout the trial. Bone mineral density of the spine (dual photon absorptiometry) showed a significant increase of more than 5% in the hormone group. There were significant decreases of 4-7% in bone mass in the placebo group over 2 yr. Biochemical estimates of bone turnover (plasma bone Gla protein, serum alkaline phosphatase, fasting urinary calcium and fasting urinary hydroxyproline) fell significantly in the hormone group, but remained unchanged in the placebo group. We conclude that continuous administration of NETA in combination with oestrogen provides effective prophylaxis against post-menopausal bone loss, although it does not produce a persistent positive calcium balance in early post-menopausal women.