The prevention of bone loss in young women treated with GnRH analogues with "add-back" estrogen therapy

Abstract

Objective: To determine whether the addition of a low dose of oral estrogen replacement therapy (ERT) taken daily can prevent the bone loss associated with continuous GnRH analogue use.

Methods: In a double-blind, placebo-controlled study, 60 women aged 21-45 years were randomized to one of three treatment groups: placebo implant every 4 weeks plus placebo ERT tablets daily, Zoladex (goserelin 3.6 mg) implant every 4 weeks plus placebo ERT tablets daily, or Zoladex (3.6 mg) implant every 4 weeks plus estradiol valerate, 2 mg/day, with norethisterone 5 mg from days 22-28. A dual x-ray bone density scan was performed before treatment and again after six treatment cycles. The percentage bone change with respect to the initial bone density was calculated.

Results: There was a significant loss of bone density at both the lumbar spine and proximal femur in the group receiving Zoladex plus placebo after 6 months compared with both pre-treatment values and with the group receiving placebo plus placebo. The addition of estrogen "add-back" therapy to GnRH analogue treatment (Zoladex plus ERT) resulted in no significant change in bone density compared with either pre-treatment values or the group receiving placebo plus placebo. The study had a dropout rate of 32%.

Conclusion: The addition of "add-back" estrogen therapy to continuous GnRH analogue use can prevent bone loss.