Effects of nafarelin on bone density

The effects of the gonadotropin-releasing hormone analog nafarelin on bone metabolism during treatment of premenopausal women for endometriosis were evaluated in two studies, both of which involved 6 months of medication followed by 6 months without medication. With low doses of nafarelin (200 micrograms/day), bone mineral measurements remained constant, whereas with high doses of the drug (400 micrograms/day) bone mineral levels decreased significantly. Within 6 months after treatment was stopped, however, bone mineral measurements returned to normal levels. Both dosages of nafarelin resulted in significant increases in bone resorption, but these determinations also returned to pretreatment values after drug therapy was stopped. In the second study, patients treated with nafarelin, 400 micrograms/day, and norethindrone, 1.2 mg/day, did not lose significant amounts of bone mineral during the treatment period.