The effect of continuous oestradiol with intermittent norgestimate on bone mineral density and bone turnover in post-menopausal women.

OBJECTIVE

To assess in post-menopausal women the efficacy and tolerability of a continuous oestradiol/intermittent norgestimate HRT regimen to prevent and to reverse post-menopausal loss of bone mineral density (BMD) and to determine the effects on serum bone turnover markers markers.

METHODS

A 1-year, multicentre, international, placebo-controlled, randomised, double-blind clinical trial was conducted in 146 post-menopausal women with an intact uterus in order to assess the effect on bone loss of continuous oral 17beta-oestradiol (1 mg per day) combined with norgestimate (90 microg per day), for 3 consecutive days out of every 6-day treatment period (E2/iNGM). During a second year extension, all women agreeing to continue were on the E2/iNGM regimen. BMD was assessed prior to treatment and after 1 and 2 years or at the end of treatment in women stopping participation prematurely after at least 6 months of treatment. Serum bone turnover markers were determined prior to and at 1 year of treatment Adverse events were collected at three-monthly intervals during clinic visits over the treatment period.

RESULTS

BMD in the lumbar spine, the primary endpoint, was evaluable in 117 subjects completing >6 months of treatment. BMD increased on average by 2.4% in women on the intermittent progestin regimen. It decreased by 1.4% in placebo treated women. The change from baseline and the difference between active and placebo treatment (Delta placebo) were highly significant (P < 0.0001). On E2/iNGM, also the BMD in the total hip increased (+1.49%, Delta placebo 3.73%, P < 0.0001). The serum markers for bone formation osteocalcin and type I collagen N-propeptide were significantly reduced compared to baseline by 31 and 44%, respectively and the bone resorption marker C-terminal crosslinked telopeptide of type I collagen by 59%. Minor increases (<10%) of markers in the placebo group were not significant. During a second year extension of the trial, all subjects were on active treatment. Subjects on placebo who lost (median+/-CI 95%) 0.66% (-2.3 to +0.5) of spine BMD during the first year now gained 4.41% (2.7-7.6). They also gained 1.6% (0.1-0.3.6) in the total hip. Subjects continuously on oestradiol/intermittent norgestimate (E2/iNGM) gained an additional 5.7% (2.3-13.5) in the lumbar spine and +0.1% (-0.6 to +2.2) at the total hip. Side effects reported by women on the intermittent progestin regimen significantly in excess over reports from the placebo group were uterine bleeding, abdominal and breast pain, but not headache. Back pain and weight gain was reported by significantly fewer women on active treatment compared to placebo.

CONCLUSIONS

The continuous oestradiol/intermittent norgestimate HRT regimen is well tolerated, reduces bone turnover and prevents post-menopausal bone loss in healthy post-menopausal women.